]> git.sesse.net Git - nageru/blobdiff - flow.cpp
Allow symlinked frame files. Useful for testing.
[nageru] / flow.cpp
index 6a9d0eeb74ce551455e2392fb963e211759aaab3..5125d26b53a5d2f09bde21132136d2a6ec333b5c 100644 (file)
--- a/flow.cpp
+++ b/flow.cpp
@@ -1,41 +1,28 @@
 #define NO_SDL_GLEXT 1
 
-#include <epoxy/gl.h>
-
-#include <SDL2/SDL.h>
-#include <SDL2/SDL_error.h>
-#include <SDL2/SDL_events.h>
-#include <SDL2/SDL_image.h>
-#include <SDL2/SDL_keyboard.h>
-#include <SDL2/SDL_mouse.h>
-#include <SDL2/SDL_video.h>
-
-#include <assert.h>
-#include <getopt.h>
-#include <stdio.h>
-#include <unistd.h>
+#include "flow.h"
 
+#include "embedded_files.h"
+#include "gpu_timers.h"
 #include "util.h"
 
 #include <algorithm>
+#include <assert.h>
 #include <deque>
-#include <memory>
+#include <dlfcn.h>
+#include <epoxy/gl.h>
 #include <map>
+#include <memory>
 #include <stack>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
 #include <vector>
 
 #define BUFFER_OFFSET(i) ((char *)nullptr + (i))
 
 using namespace std;
 
-SDL_Window *window;
-
-// Operating point 3 (10 Hz on CPU, excluding preprocessing).
-constexpr float patch_overlap_ratio = 0.75f;
-constexpr unsigned coarsest_level = 5;
-constexpr unsigned finest_level = 1;
-constexpr unsigned patch_size_pixels = 12;
-
 // Weighting constants for the different parts of the variational refinement.
 // These don't correspond 1:1 to the values given in the DIS paper,
 // since we have different normalizations and ranges in some cases.
@@ -43,26 +30,15 @@ constexpr unsigned patch_size_pixels = 12;
 // although the error (EPE) seems to be fairly insensitive to the precise values.
 // Only the relative values matter, so we fix alpha (the smoothness constant)
 // at unity and tweak the others.
+//
+// TODO: Maybe this should not be global.
 float vr_alpha = 1.0f, vr_delta = 0.25f, vr_gamma = 0.25f;
 
-bool enable_timing = true;
-bool enable_variational_refinement = true;  // Just for debugging.
-bool enable_interpolation = false;
-
 // Some global OpenGL objects.
 // TODO: These should really be part of DISComputeFlow.
 GLuint nearest_sampler, linear_sampler, zero_border_sampler;
 GLuint vertex_vbo;
 
-// Structures for asynchronous readback. We assume everything is the same size (and GL_RG16F).
-struct ReadInProgress {
-       GLuint pbo;
-       string filename0, filename1;
-       string flow_filename, ppm_filename;  // Either may be empty for no write.
-};
-stack<GLuint> spare_pbos;
-deque<ReadInProgress> reads_in_progress;
-
 int find_num_levels(int width, int height)
 {
        int levels = 1;
@@ -74,10 +50,18 @@ int find_num_levels(int width, int height)
        return levels;
 }
 
-string read_file(const string &filename)
+string read_file(const string &filename, const unsigned char *start = nullptr, const size_t size = 0)
 {
        FILE *fp = fopen(filename.c_str(), "r");
        if (fp == nullptr) {
+               // Fall back to the version we compiled in. (We prefer disk if we can,
+               // since that makes it possible to work on shaders without recompiling
+               // all the time.)
+               if (start != nullptr) {
+                       return string(reinterpret_cast<const char *>(start),
+                               reinterpret_cast<const char *>(start) + size);
+               }
+
                perror(filename.c_str());
                exit(1);
        }
@@ -88,7 +72,7 @@ string read_file(const string &filename)
                exit(1);
        }
 
-       int size = ftell(fp);
+       int disk_size = ftell(fp);
 
        ret = fseek(fp, 0, SEEK_SET);
        if (ret == -1) {
@@ -97,15 +81,15 @@ string read_file(const string &filename)
        }
 
        string str;
-       str.resize(size);
-       ret = fread(&str[0], size, 1, fp);
+       str.resize(disk_size);
+       ret = fread(&str[0], disk_size, 1, fp);
        if (ret == -1) {
                perror("fread");
                exit(1);
        }
        if (ret == 0) {
                fprintf(stderr, "Short read when trying to read %d bytes from %s\n",
-                               size, filename.c_str());
+                       disk_size, filename.c_str());
                exit(1);
        }
        fclose(fp);
@@ -113,11 +97,10 @@ string read_file(const string &filename)
        return str;
 }
 
-
 GLuint compile_shader(const string &shader_src, GLenum type)
 {
        GLuint obj = glCreateShader(type);
-       const GLcharsource[] = { shader_src.data() };
+       const GLchar *source[] = { shader_src.data() };
        const GLint length[] = { (GLint)shader_src.size() };
        glShaderSource(obj, 1, source, length);
        glCompileShader(obj);
@@ -152,57 +135,6 @@ GLuint compile_shader(const string &shader_src, GLenum type)
        return obj;
 }
 
-enum MipmapPolicy {
-       WITHOUT_MIPMAPS,
-       WITH_MIPMAPS
-};
-
-GLuint load_texture(const char *filename, unsigned *width_ret, unsigned *height_ret, MipmapPolicy mipmaps)
-{
-       SDL_Surface *surf = IMG_Load(filename);
-       if (surf == nullptr) {
-               fprintf(stderr, "IMG_Load(%s): %s\n", filename, IMG_GetError());
-               exit(1);
-       }
-
-       // For whatever reason, SDL doesn't support converting to YUV surfaces
-       // nor grayscale, so we'll do it ourselves.
-       SDL_Surface *rgb_surf = SDL_ConvertSurfaceFormat(surf, SDL_PIXELFORMAT_RGBA32, /*flags=*/0);
-       if (rgb_surf == nullptr) {
-               fprintf(stderr, "SDL_ConvertSurfaceFormat(%s): %s\n", filename, SDL_GetError());
-               exit(1);
-       }
-
-       SDL_FreeSurface(surf);
-
-       unsigned width = rgb_surf->w, height = rgb_surf->h;
-       const uint8_t *sptr = (uint8_t *)rgb_surf->pixels;
-       unique_ptr<uint8_t[]> pix(new uint8_t[width * height * 4]);
-
-       // Extract the Y component, and convert to bottom-left origin.
-       for (unsigned y = 0; y < height; ++y) {
-               unsigned y2 = height - 1 - y;
-               memcpy(pix.get() + y * width * 4, sptr + y2 * rgb_surf->pitch, width * 4);
-       }
-       SDL_FreeSurface(rgb_surf);
-
-       int num_levels = (mipmaps == WITH_MIPMAPS) ? find_num_levels(width, height) : 1;
-
-       GLuint tex;
-       glCreateTextures(GL_TEXTURE_2D, 1, &tex);
-       glTextureStorage2D(tex, num_levels, GL_RGBA8, width, height);
-       glTextureSubImage2D(tex, 0, 0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, pix.get());
-
-       if (mipmaps == WITH_MIPMAPS) {
-               glGenerateTextureMipmap(tex);
-       }
-
-       *width_ret = width;
-       *height_ret = height;
-
-       return tex;
-}
-
 GLuint link_program(GLuint vs_obj, GLuint fs_obj)
 {
        GLuint program = glCreateProgram();
@@ -220,32 +152,6 @@ GLuint link_program(GLuint vs_obj, GLuint fs_obj)
        return program;
 }
 
-GLuint generate_vbo(GLint size, GLsizeiptr data_size, const GLvoid *data)
-{
-       GLuint vbo;
-       glCreateBuffers(1, &vbo);
-       glBufferData(GL_ARRAY_BUFFER, data_size, data, GL_STATIC_DRAW);
-       glNamedBufferData(vbo, data_size, data, GL_STATIC_DRAW);
-       return vbo;
-}
-
-GLuint fill_vertex_attribute(GLuint vao, GLuint glsl_program_num, const string &attribute_name, GLint size, GLenum type, GLsizeiptr data_size, const GLvoid *data)
-{
-       int attrib = glGetAttribLocation(glsl_program_num, attribute_name.c_str());
-       if (attrib == -1) {
-               return -1;
-       }
-
-       GLuint vbo = generate_vbo(size, data_size, data);
-
-       glBindBuffer(GL_ARRAY_BUFFER, vbo);
-       glEnableVertexArrayAttrib(vao, attrib);
-       glVertexAttribPointer(attrib, size, type, GL_FALSE, 0, BUFFER_OFFSET(0));
-       glBindBuffer(GL_ARRAY_BUFFER, 0);
-
-       return vbo;
-}
-
 void bind_sampler(GLuint program, GLint location, GLuint texture_unit, GLuint tex, GLuint sampler)
 {
        if (location == -1) {
@@ -257,36 +163,6 @@ void bind_sampler(GLuint program, GLint location, GLuint texture_unit, GLuint te
        glProgramUniform1i(program, location, texture_unit);
 }
 
-// A class that caches FBOs that render to a given set of textures.
-// It never frees anything, so it is only suitable for rendering to
-// the same (small) set of textures over and over again.
-template<size_t num_elements>
-class PersistentFBOSet {
-public:
-       void render_to(const array<GLuint, num_elements> &textures);
-
-       // Convenience wrappers.
-       void render_to(GLuint texture0, enable_if<num_elements == 1> * = nullptr) {
-               render_to({{texture0}});
-       }
-
-       void render_to(GLuint texture0, GLuint texture1, enable_if<num_elements == 2> * = nullptr) {
-               render_to({{texture0, texture1}});
-       }
-
-       void render_to(GLuint texture0, GLuint texture1, GLuint texture2, enable_if<num_elements == 3> * = nullptr) {
-               render_to({{texture0, texture1, texture2}});
-       }
-
-       void render_to(GLuint texture0, GLuint texture1, GLuint texture2, GLuint texture3, enable_if<num_elements == 4> * = nullptr) {
-               render_to({{texture0, texture1, texture2, texture3}});
-       }
-
-private:
-       // TODO: Delete these on destruction.
-       map<array<GLuint, num_elements>, GLuint> fbos;
-};
-
 template<size_t num_elements>
 void PersistentFBOSet<num_elements>::render_to(const array<GLuint, num_elements> &textures)
 {
@@ -309,26 +185,35 @@ void PersistentFBOSet<num_elements>::render_to(const array<GLuint, num_elements>
        glBindFramebuffer(GL_FRAMEBUFFER, fbo);
 }
 
-// Convert RGB to grayscale, using Rec. 709 coefficients.
-class GrayscaleConversion {
-public:
-       GrayscaleConversion();
-       void exec(GLint tex, GLint gray_tex, int width, int height);
+template<size_t num_elements>
+void PersistentFBOSetWithDepth<num_elements>::render_to(GLuint depth_rb, const array<GLuint, num_elements> &textures)
+{
+       auto key = make_pair(depth_rb, textures);
+
+       auto it = fbos.find(key);
+       if (it != fbos.end()) {
+               glBindFramebuffer(GL_FRAMEBUFFER, it->second);
+               return;
+       }
 
-private:
-       PersistentFBOSet<1> fbos;
-       GLuint gray_vs_obj;
-       GLuint gray_fs_obj;
-       GLuint gray_program;
-       GLuint gray_vao;
+       GLuint fbo;
+       glCreateFramebuffers(1, &fbo);
+       GLenum bufs[num_elements];
+       glNamedFramebufferRenderbuffer(fbo, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depth_rb);
+       for (size_t i = 0; i < num_elements; ++i) {
+               glNamedFramebufferTexture(fbo, GL_COLOR_ATTACHMENT0 + i, textures[i], 0);
+               bufs[i] = GL_COLOR_ATTACHMENT0 + i;
+       }
+       glNamedFramebufferDrawBuffers(fbo, num_elements, bufs);
 
-       GLuint uniform_tex;
-};
+       fbos[key] = fbo;
+       glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+}
 
 GrayscaleConversion::GrayscaleConversion()
 {
-       gray_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
-       gray_fs_obj = compile_shader(read_file("gray.frag"), GL_FRAGMENT_SHADER);
+       gray_vs_obj = compile_shader(read_file("vs.vert", _binary_vs_vert_data, _binary_vs_vert_size), GL_VERTEX_SHADER);
+       gray_fs_obj = compile_shader(read_file("gray.frag", _binary_gray_frag_data, _binary_gray_frag_size), GL_FRAGMENT_SHADER);
        gray_program = link_program(gray_vs_obj, gray_fs_obj);
 
        // Set up the VAO containing all the required position/texcoord data.
@@ -342,7 +227,7 @@ GrayscaleConversion::GrayscaleConversion()
        uniform_tex = glGetUniformLocation(gray_program, "tex");
 }
 
-void GrayscaleConversion::exec(GLint tex, GLint gray_tex, int width, int height)
+void GrayscaleConversion::exec(GLint tex, GLint gray_tex, int width, int height, int num_layers)
 {
        glUseProgram(gray_program);
        bind_sampler(gray_program, uniform_tex, 0, tex, nearest_sampler);
@@ -350,301 +235,131 @@ void GrayscaleConversion::exec(GLint tex, GLint gray_tex, int width, int height)
        glViewport(0, 0, width, height);
        fbos.render_to(gray_tex);
        glBindVertexArray(gray_vao);
-       glUseProgram(gray_program);
        glDisable(GL_BLEND);
-       glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, num_layers);
 }
 
-// Compute gradients in every point, used for the motion search.
-// The DIS paper doesn't actually mention how these are computed,
-// but seemingly, a 3x3 Sobel operator is used here (at least in
-// later versions of the code), while a [1 -8 0 8 -1] kernel is
-// used for all the derivatives in the variational refinement part
-// (which borrows code from DeepFlow). This is inconsistent,
-// but I guess we're better off with staying with the original
-// decisions until we actually know having different ones would be better.
-class Sobel {
-public:
-       Sobel();
-       void exec(GLint tex0_view, GLint grad0_tex, int level_width, int level_height);
-
-private:
-       PersistentFBOSet<1> fbos;
-       GLuint sobel_vs_obj;
-       GLuint sobel_fs_obj;
-       GLuint sobel_program;
-       GLuint sobel_vao;
-
-       GLuint uniform_tex;
-};
-
 Sobel::Sobel()
 {
-       sobel_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
-       sobel_fs_obj = compile_shader(read_file("sobel.frag"), GL_FRAGMENT_SHADER);
+       sobel_vs_obj = compile_shader(read_file("vs.vert", _binary_vs_vert_data, _binary_vs_vert_size), GL_VERTEX_SHADER);
+       sobel_fs_obj = compile_shader(read_file("sobel.frag", _binary_sobel_frag_data, _binary_sobel_frag_size), GL_FRAGMENT_SHADER);
        sobel_program = link_program(sobel_vs_obj, sobel_fs_obj);
 
-       // Set up the VAO containing all the required position/texcoord data.
-       glCreateVertexArrays(1, &sobel_vao);
-       glBindVertexArray(sobel_vao);
-
-       GLint position_attrib = glGetAttribLocation(sobel_program, "position");
-       glEnableVertexArrayAttrib(sobel_vao, position_attrib);
-       glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
-
        uniform_tex = glGetUniformLocation(sobel_program, "tex");
 }
 
-void Sobel::exec(GLint tex0_view, GLint grad0_tex, int level_width, int level_height)
+void Sobel::exec(GLint tex_view, GLint grad_tex, int level_width, int level_height, int num_layers)
 {
        glUseProgram(sobel_program);
-       bind_sampler(sobel_program, uniform_tex, 0, tex0_view, nearest_sampler);
+       bind_sampler(sobel_program, uniform_tex, 0, tex_view, nearest_sampler);
 
        glViewport(0, 0, level_width, level_height);
-       fbos.render_to(grad0_tex);
-       glBindVertexArray(sobel_vao);
-       glUseProgram(sobel_program);
+       fbos.render_to(grad_tex);
        glDisable(GL_BLEND);
-       glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, num_layers);
 }
 
-// Motion search to find the initial flow. See motion_search.frag for documentation.
-class MotionSearch {
-public:
-       MotionSearch();
-       void exec(GLuint tex0_view, GLuint tex1_view, GLuint grad0_tex, GLuint flow_tex, GLuint flow_out_tex, int level_width, int level_height, int prev_level_width, int prev_level_height, int width_patches, int height_patches);
-
-private:
-       PersistentFBOSet<1> fbos;
-
-       GLuint motion_vs_obj;
-       GLuint motion_fs_obj;
-       GLuint motion_search_program;
-       GLuint motion_search_vao;
-
-       GLuint uniform_inv_image_size, uniform_inv_prev_level_size;
-       GLuint uniform_image0_tex, uniform_image1_tex, uniform_grad0_tex, uniform_flow_tex;
-};
-
-MotionSearch::MotionSearch()
+MotionSearch::MotionSearch(const OperatingPoint &op)
+       : op(op)
 {
-       motion_vs_obj = compile_shader(read_file("motion_search.vert"), GL_VERTEX_SHADER);
-       motion_fs_obj = compile_shader(read_file("motion_search.frag"), GL_FRAGMENT_SHADER);
+       motion_vs_obj = compile_shader(read_file("motion_search.vert", _binary_motion_search_vert_data, _binary_motion_search_vert_size), GL_VERTEX_SHADER);
+       motion_fs_obj = compile_shader(read_file("motion_search.frag", _binary_motion_search_frag_data, _binary_motion_search_frag_size), GL_FRAGMENT_SHADER);
        motion_search_program = link_program(motion_vs_obj, motion_fs_obj);
 
-       // Set up the VAO containing all the required position/texcoord data.
-       glCreateVertexArrays(1, &motion_search_vao);
-       glBindVertexArray(motion_search_vao);
-       glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
-
-       GLint position_attrib = glGetAttribLocation(motion_search_program, "position");
-       glEnableVertexArrayAttrib(motion_search_vao, position_attrib);
-       glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
-
        uniform_inv_image_size = glGetUniformLocation(motion_search_program, "inv_image_size");
        uniform_inv_prev_level_size = glGetUniformLocation(motion_search_program, "inv_prev_level_size");
-       uniform_image0_tex = glGetUniformLocation(motion_search_program, "image0_tex");
-       uniform_image1_tex = glGetUniformLocation(motion_search_program, "image1_tex");
-       uniform_grad0_tex = glGetUniformLocation(motion_search_program, "grad0_tex");
+       uniform_out_flow_size = glGetUniformLocation(motion_search_program, "out_flow_size");
+       uniform_image_tex = glGetUniformLocation(motion_search_program, "image_tex");
+       uniform_grad_tex = glGetUniformLocation(motion_search_program, "grad_tex");
        uniform_flow_tex = glGetUniformLocation(motion_search_program, "flow_tex");
+       uniform_patch_size = glGetUniformLocation(motion_search_program, "patch_size");
+       uniform_num_iterations = glGetUniformLocation(motion_search_program, "num_iterations");
 }
 
-void MotionSearch::exec(GLuint tex0_view, GLuint tex1_view, GLuint grad0_tex, GLuint flow_tex, GLuint flow_out_tex, int level_width, int level_height, int prev_level_width, int prev_level_height, int width_patches, int height_patches)
+void MotionSearch::exec(GLuint tex_view, GLuint grad_tex, GLuint flow_tex, GLuint flow_out_tex, int level_width, int level_height, int prev_level_width, int prev_level_height, int width_patches, int height_patches, int num_layers)
 {
        glUseProgram(motion_search_program);
 
-       bind_sampler(motion_search_program, uniform_image0_tex, 0, tex0_view, nearest_sampler);
-       bind_sampler(motion_search_program, uniform_image1_tex, 1, tex1_view, linear_sampler);
-       bind_sampler(motion_search_program, uniform_grad0_tex, 2, grad0_tex, zero_border_sampler);
-       bind_sampler(motion_search_program, uniform_flow_tex, 3, flow_tex, linear_sampler);
+       bind_sampler(motion_search_program, uniform_image_tex, 0, tex_view, linear_sampler);
+       bind_sampler(motion_search_program, uniform_grad_tex, 1, grad_tex, nearest_sampler);
+       bind_sampler(motion_search_program, uniform_flow_tex, 2, flow_tex, linear_sampler);
 
        glProgramUniform2f(motion_search_program, uniform_inv_image_size, 1.0f / level_width, 1.0f / level_height);
        glProgramUniform2f(motion_search_program, uniform_inv_prev_level_size, 1.0f / prev_level_width, 1.0f / prev_level_height);
+       glProgramUniform2f(motion_search_program, uniform_out_flow_size, width_patches, height_patches);
+       glProgramUniform1ui(motion_search_program, uniform_patch_size, op.patch_size_pixels);
+       glProgramUniform1ui(motion_search_program, uniform_num_iterations, op.search_iterations);
 
        glViewport(0, 0, width_patches, height_patches);
        fbos.render_to(flow_out_tex);
-       glBindVertexArray(motion_search_vao);
-       glUseProgram(motion_search_program);
-       glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, num_layers);
 }
 
-// Do “densification”, ie., upsampling of the flow patches to the flow field
-// (the same size as the image at this level). We draw one quad per patch
-// over its entire covered area (using instancing in the vertex shader),
-// and then weight the contributions in the pixel shader by post-warp difference.
-// This is equation (3) in the paper.
-//
-// We accumulate the flow vectors in the R/G channels (for u/v) and the total
-// weight in the B channel. Dividing R and G by B gives the normalized values.
-class Densify {
-public:
-       Densify();
-       void exec(GLuint tex0_view, GLuint tex1_view, GLuint flow_tex, GLuint dense_flow_tex, int level_width, int level_height, int width_patches, int height_patches);
-
-private:
-       PersistentFBOSet<1> fbos;
-
-       GLuint densify_vs_obj;
-       GLuint densify_fs_obj;
-       GLuint densify_program;
-       GLuint densify_vao;
-
-       GLuint uniform_patch_size, uniform_patch_spacing;
-       GLuint uniform_image0_tex, uniform_image1_tex, uniform_flow_tex;
-};
-
-Densify::Densify()
+Densify::Densify(const OperatingPoint &op)
+       : op(op)
 {
-       densify_vs_obj = compile_shader(read_file("densify.vert"), GL_VERTEX_SHADER);
-       densify_fs_obj = compile_shader(read_file("densify.frag"), GL_FRAGMENT_SHADER);
+       densify_vs_obj = compile_shader(read_file("densify.vert", _binary_densify_vert_data, _binary_densify_vert_size), GL_VERTEX_SHADER);
+       densify_fs_obj = compile_shader(read_file("densify.frag", _binary_densify_frag_data, _binary_densify_frag_size), GL_FRAGMENT_SHADER);
        densify_program = link_program(densify_vs_obj, densify_fs_obj);
 
-       // Set up the VAO containing all the required position/texcoord data.
-       glCreateVertexArrays(1, &densify_vao);
-       glBindVertexArray(densify_vao);
-       glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
-
-       GLint position_attrib = glGetAttribLocation(densify_program, "position");
-       glEnableVertexArrayAttrib(densify_vao, position_attrib);
-       glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
-
        uniform_patch_size = glGetUniformLocation(densify_program, "patch_size");
-       uniform_patch_spacing = glGetUniformLocation(densify_program, "patch_spacing");
-       uniform_image0_tex = glGetUniformLocation(densify_program, "image0_tex");
-       uniform_image1_tex = glGetUniformLocation(densify_program, "image1_tex");
+       uniform_image_tex = glGetUniformLocation(densify_program, "image_tex");
        uniform_flow_tex = glGetUniformLocation(densify_program, "flow_tex");
 }
 
-void Densify::exec(GLuint tex0_view, GLuint tex1_view, GLuint flow_tex, GLuint dense_flow_tex, int level_width, int level_height, int width_patches, int height_patches)
+void Densify::exec(GLuint tex_view, GLuint flow_tex, GLuint dense_flow_tex, int level_width, int level_height, int width_patches, int height_patches, int num_layers)
 {
        glUseProgram(densify_program);
 
-       bind_sampler(densify_program, uniform_image0_tex, 0, tex0_view, nearest_sampler);
-       bind_sampler(densify_program, uniform_image1_tex, 1, tex1_view, linear_sampler);
-       bind_sampler(densify_program, uniform_flow_tex, 2, flow_tex, nearest_sampler);
+       bind_sampler(densify_program, uniform_image_tex, 0, tex_view, linear_sampler);
+       bind_sampler(densify_program, uniform_flow_tex, 1, flow_tex, nearest_sampler);
 
        glProgramUniform2f(densify_program, uniform_patch_size,
-               float(patch_size_pixels) / level_width,
-               float(patch_size_pixels) / level_height);
-
-       float patch_spacing_x = float(level_width - patch_size_pixels) / (width_patches - 1);
-       float patch_spacing_y = float(level_height - patch_size_pixels) / (height_patches - 1);
-       if (width_patches == 1) patch_spacing_x = 0.0f;  // Avoid infinities.
-       if (height_patches == 1) patch_spacing_y = 0.0f;
-       glProgramUniform2f(densify_program, uniform_patch_spacing,
-               patch_spacing_x / level_width,
-               patch_spacing_y / level_height);
+               float(op.patch_size_pixels) / level_width,
+               float(op.patch_size_pixels) / level_height);
 
        glViewport(0, 0, level_width, level_height);
        glEnable(GL_BLEND);
        glBlendFunc(GL_ONE, GL_ONE);
-       glBindVertexArray(densify_vao);
        fbos.render_to(dense_flow_tex);
-       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, width_patches * height_patches);
+       glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
+       glClear(GL_COLOR_BUFFER_BIT);
+       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, width_patches * height_patches * num_layers);
 }
 
-// Warp I_1 to I_w, and then compute the mean (I) and difference (I_t) of
-// I_0 and I_w. The prewarping is what enables us to solve the variational
-// flow for du,dv instead of u,v.
-//
-// Also calculates the normalized flow, ie. divides by z (this is needed because
-// Densify works by additive blending) and multiplies by the image size.
-//
-// See variational_refinement.txt for more information.
-class Prewarp {
-public:
-       Prewarp();
-       void exec(GLuint tex0_view, GLuint tex1_view, GLuint flow_tex, GLuint normalized_flow_tex, GLuint I_tex, GLuint I_t_tex, int level_width, int level_height);
-
-private:
-       PersistentFBOSet<3> fbos;
-
-       GLuint prewarp_vs_obj;
-       GLuint prewarp_fs_obj;
-       GLuint prewarp_program;
-       GLuint prewarp_vao;
-
-       GLuint uniform_image0_tex, uniform_image1_tex, uniform_flow_tex;
-};
-
 Prewarp::Prewarp()
 {
-       prewarp_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
-       prewarp_fs_obj = compile_shader(read_file("prewarp.frag"), GL_FRAGMENT_SHADER);
+       prewarp_vs_obj = compile_shader(read_file("vs.vert", _binary_vs_vert_data, _binary_vs_vert_size), GL_VERTEX_SHADER);
+       prewarp_fs_obj = compile_shader(read_file("prewarp.frag", _binary_prewarp_frag_data, _binary_prewarp_frag_size), GL_FRAGMENT_SHADER);
        prewarp_program = link_program(prewarp_vs_obj, prewarp_fs_obj);
 
-       // Set up the VAO containing all the required position/texcoord data.
-       glCreateVertexArrays(1, &prewarp_vao);
-       glBindVertexArray(prewarp_vao);
-       glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
-
-       GLint position_attrib = glGetAttribLocation(prewarp_program, "position");
-       glEnableVertexArrayAttrib(prewarp_vao, position_attrib);
-       glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
-
-       uniform_image0_tex = glGetUniformLocation(prewarp_program, "image0_tex");
-       uniform_image1_tex = glGetUniformLocation(prewarp_program, "image1_tex");
+       uniform_image_tex = glGetUniformLocation(prewarp_program, "image_tex");
        uniform_flow_tex = glGetUniformLocation(prewarp_program, "flow_tex");
 }
 
-void Prewarp::exec(GLuint tex0_view, GLuint tex1_view, GLuint flow_tex, GLuint I_tex, GLuint I_t_tex, GLuint normalized_flow_tex, int level_width, int level_height)
+void Prewarp::exec(GLuint tex_view, GLuint flow_tex, GLuint I_tex, GLuint I_t_tex, GLuint normalized_flow_tex, int level_width, int level_height, int num_layers)
 {
        glUseProgram(prewarp_program);
 
-       bind_sampler(prewarp_program, uniform_image0_tex, 0, tex0_view, nearest_sampler);
-       bind_sampler(prewarp_program, uniform_image1_tex, 1, tex1_view, linear_sampler);
-       bind_sampler(prewarp_program, uniform_flow_tex, 2, flow_tex, nearest_sampler);
+       bind_sampler(prewarp_program, uniform_image_tex, 0, tex_view, linear_sampler);
+       bind_sampler(prewarp_program, uniform_flow_tex, 1, flow_tex, nearest_sampler);
 
        glViewport(0, 0, level_width, level_height);
        glDisable(GL_BLEND);
-       glBindVertexArray(prewarp_vao);
        fbos.render_to(I_tex, I_t_tex, normalized_flow_tex);
-       glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, num_layers);
 }
 
-// From I, calculate the partial derivatives I_x and I_y. We use a four-tap
-// central difference filter, since apparently, that's tradition (I haven't
-// measured quality versus a more normal 0.5 (I[x+1] - I[x-1]).)
-// The coefficients come from
-//
-//   https://en.wikipedia.org/wiki/Finite_difference_coefficient
-//
-// Also computes β_0, since it depends only on I_x and I_y.
-class Derivatives {
-public:
-       Derivatives();
-       void exec(GLuint input_tex, GLuint I_x_y_tex, GLuint beta_0_tex, int level_width, int level_height);
-
-private:
-       PersistentFBOSet<2> fbos;
-
-       GLuint derivatives_vs_obj;
-       GLuint derivatives_fs_obj;
-       GLuint derivatives_program;
-       GLuint derivatives_vao;
-
-       GLuint uniform_tex;
-};
-
 Derivatives::Derivatives()
 {
-       derivatives_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
-       derivatives_fs_obj = compile_shader(read_file("derivatives.frag"), GL_FRAGMENT_SHADER);
+       derivatives_vs_obj = compile_shader(read_file("vs.vert", _binary_vs_vert_data, _binary_vs_vert_size), GL_VERTEX_SHADER);
+       derivatives_fs_obj = compile_shader(read_file("derivatives.frag", _binary_derivatives_frag_data, _binary_derivatives_frag_size), GL_FRAGMENT_SHADER);
        derivatives_program = link_program(derivatives_vs_obj, derivatives_fs_obj);
 
-       // Set up the VAO containing all the required position/texcoord data.
-       glCreateVertexArrays(1, &derivatives_vao);
-       glBindVertexArray(derivatives_vao);
-       glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
-
-       GLint position_attrib = glGetAttribLocation(derivatives_program, "position");
-       glEnableVertexArrayAttrib(derivatives_vao, position_attrib);
-       glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
-
        uniform_tex = glGetUniformLocation(derivatives_program, "tex");
 }
 
-void Derivatives::exec(GLuint input_tex, GLuint I_x_y_tex, GLuint beta_0_tex, int level_width, int level_height)
+void Derivatives::exec(GLuint input_tex, GLuint I_x_y_tex, GLuint beta_0_tex, int level_width, int level_height, int num_layers)
 {
        glUseProgram(derivatives_program);
 
@@ -652,135 +367,56 @@ void Derivatives::exec(GLuint input_tex, GLuint I_x_y_tex, GLuint beta_0_tex, in
 
        glViewport(0, 0, level_width, level_height);
        glDisable(GL_BLEND);
-       glBindVertexArray(derivatives_vao);
        fbos.render_to(I_x_y_tex, beta_0_tex);
-       glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, num_layers);
 }
 
-// Calculate the smoothness constraints between neighboring pixels;
-// s_x(x,y) stores smoothness between pixel (x,y) and (x+1,y),
-// and s_y(x,y) stores between (x,y) and (x,y+1). We'll sample with
-// border color (0,0) later, so that there's zero diffusion out of
-// the border.
-//
-// See variational_refinement.txt for more information.
-class ComputeSmoothness {
-public:
-       ComputeSmoothness();
-       void exec(GLuint flow_tex, GLuint diff_flow_tex, GLuint smoothness_x_tex, GLuint smoothness_y_tex, int level_width, int level_height);
-
-private:
-       PersistentFBOSet<2> fbos;
-
-       GLuint smoothness_vs_obj;
-       GLuint smoothness_fs_obj;
-       GLuint smoothness_program;
-       GLuint smoothness_vao;
-
-       GLuint uniform_flow_tex, uniform_diff_flow_tex;
-       GLuint uniform_alpha;
-};
-
-ComputeSmoothness::ComputeSmoothness()
+ComputeDiffusivity::ComputeDiffusivity()
 {
-       smoothness_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
-       smoothness_fs_obj = compile_shader(read_file("smoothness.frag"), GL_FRAGMENT_SHADER);
-       smoothness_program = link_program(smoothness_vs_obj, smoothness_fs_obj);
-
-       // Set up the VAO containing all the required position/texcoord data.
-       glCreateVertexArrays(1, &smoothness_vao);
-       glBindVertexArray(smoothness_vao);
-       glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
-
-       GLint position_attrib = glGetAttribLocation(smoothness_program, "position");
-       glEnableVertexArrayAttrib(smoothness_vao, position_attrib);
-       glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
-
-       uniform_flow_tex = glGetUniformLocation(smoothness_program, "flow_tex");
-       uniform_diff_flow_tex = glGetUniformLocation(smoothness_program, "diff_flow_tex");
-       uniform_alpha = glGetUniformLocation(smoothness_program, "alpha");
+       diffusivity_vs_obj = compile_shader(read_file("vs.vert", _binary_vs_vert_data, _binary_vs_vert_size), GL_VERTEX_SHADER);
+       diffusivity_fs_obj = compile_shader(read_file("diffusivity.frag", _binary_diffusivity_frag_data, _binary_diffusivity_frag_size), GL_FRAGMENT_SHADER);
+       diffusivity_program = link_program(diffusivity_vs_obj, diffusivity_fs_obj);
+
+       uniform_flow_tex = glGetUniformLocation(diffusivity_program, "flow_tex");
+       uniform_diff_flow_tex = glGetUniformLocation(diffusivity_program, "diff_flow_tex");
+       uniform_alpha = glGetUniformLocation(diffusivity_program, "alpha");
+       uniform_zero_diff_flow = glGetUniformLocation(diffusivity_program, "zero_diff_flow");
 }
 
-void ComputeSmoothness::exec(GLuint flow_tex, GLuint diff_flow_tex, GLuint smoothness_x_tex, GLuint smoothness_y_tex, int level_width, int level_height)
+void ComputeDiffusivity::exec(GLuint flow_tex, GLuint diff_flow_tex, GLuint diffusivity_tex, int level_width, int level_height, bool zero_diff_flow, int num_layers)
 {
-       glUseProgram(smoothness_program);
+       glUseProgram(diffusivity_program);
 
-       bind_sampler(smoothness_program, uniform_flow_tex, 0, flow_tex, nearest_sampler);
-       bind_sampler(smoothness_program, uniform_diff_flow_tex, 1, diff_flow_tex, nearest_sampler);
-       glProgramUniform1f(smoothness_program, uniform_alpha, vr_alpha);
+       bind_sampler(diffusivity_program, uniform_flow_tex, 0, flow_tex, nearest_sampler);
+       bind_sampler(diffusivity_program, uniform_diff_flow_tex, 1, diff_flow_tex, nearest_sampler);
+       glProgramUniform1f(diffusivity_program, uniform_alpha, vr_alpha);
+       glProgramUniform1i(diffusivity_program, uniform_zero_diff_flow, zero_diff_flow);
 
        glViewport(0, 0, level_width, level_height);
 
        glDisable(GL_BLEND);
-       glBindVertexArray(smoothness_vao);
-       fbos.render_to(smoothness_x_tex, smoothness_y_tex);
-       glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
-
-       // Make sure the smoothness on the right and upper borders is zero.
-       // We could have done this by making (W-1)xH and Wx(H-1) textures instead
-       // (we're sampling smoothness with all-zero border color), but we'd
-       // have to adjust the sampling coordinates, which is annoying.
-       glClearTexSubImage(smoothness_x_tex, 0,  level_width - 1, 0, 0,   1, level_height, 1,  GL_RED, GL_FLOAT, nullptr);
-       glClearTexSubImage(smoothness_y_tex, 0,  0, level_height - 1, 0,  level_width, 1, 1,   GL_RED, GL_FLOAT, nullptr);
+       fbos.render_to(diffusivity_tex);
+       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, num_layers);
 }
 
-// Set up the equations set (two equations in two unknowns, per pixel).
-// We store five floats; the three non-redundant elements of the 2x2 matrix (A)
-// as 32-bit floats, and the two elements on the right-hand side (b) as 16-bit
-// floats. (Actually, we store the inverse of the diagonal elements, because
-// we only ever need to divide by them.) This fits into four u32 values;
-// R, G, B for the matrix (the last element is symmetric) and A for the two b values.
-// All the values of the energy term (E_I, E_G, E_S), except the smoothness
-// terms that depend on other pixels, are calculated in one pass.
-//
-// See variational_refinement.txt for more information.
-class SetupEquations {
-public:
-       SetupEquations();
-       void exec(GLuint I_x_y_tex, GLuint I_t_tex, GLuint diff_flow_tex, GLuint flow_tex, GLuint beta_0_tex, GLuint smoothness_x_tex, GLuint smoothness_y_tex, GLuint equation_tex, int level_width, int level_height);
-
-private:
-       PersistentFBOSet<1> fbos;
-
-       GLuint equations_vs_obj;
-       GLuint equations_fs_obj;
-       GLuint equations_program;
-       GLuint equations_vao;
-
-       GLuint uniform_I_x_y_tex, uniform_I_t_tex;
-       GLuint uniform_diff_flow_tex, uniform_base_flow_tex;
-       GLuint uniform_beta_0_tex;
-       GLuint uniform_smoothness_x_tex, uniform_smoothness_y_tex;
-       GLuint uniform_gamma, uniform_delta;
-};
-
 SetupEquations::SetupEquations()
 {
-       equations_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
-       equations_fs_obj = compile_shader(read_file("equations.frag"), GL_FRAGMENT_SHADER);
+       equations_vs_obj = compile_shader(read_file("equations.vert", _binary_equations_vert_data, _binary_equations_vert_size), GL_VERTEX_SHADER);
+       equations_fs_obj = compile_shader(read_file("equations.frag", _binary_equations_frag_data, _binary_equations_frag_size), GL_FRAGMENT_SHADER);
        equations_program = link_program(equations_vs_obj, equations_fs_obj);
 
-       // Set up the VAO containing all the required position/texcoord data.
-       glCreateVertexArrays(1, &equations_vao);
-       glBindVertexArray(equations_vao);
-       glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
-
-       GLint position_attrib = glGetAttribLocation(equations_program, "position");
-       glEnableVertexArrayAttrib(equations_vao, position_attrib);
-       glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
-
        uniform_I_x_y_tex = glGetUniformLocation(equations_program, "I_x_y_tex");
        uniform_I_t_tex = glGetUniformLocation(equations_program, "I_t_tex");
        uniform_diff_flow_tex = glGetUniformLocation(equations_program, "diff_flow_tex");
        uniform_base_flow_tex = glGetUniformLocation(equations_program, "base_flow_tex");
        uniform_beta_0_tex = glGetUniformLocation(equations_program, "beta_0_tex");
-       uniform_smoothness_x_tex = glGetUniformLocation(equations_program, "smoothness_x_tex");
-       uniform_smoothness_y_tex = glGetUniformLocation(equations_program, "smoothness_y_tex");
+       uniform_diffusivity_tex = glGetUniformLocation(equations_program, "diffusivity_tex");
        uniform_gamma = glGetUniformLocation(equations_program, "gamma");
        uniform_delta = glGetUniformLocation(equations_program, "delta");
+       uniform_zero_diff_flow = glGetUniformLocation(equations_program, "zero_diff_flow");
 }
 
-void SetupEquations::exec(GLuint I_x_y_tex, GLuint I_t_tex, GLuint diff_flow_tex, GLuint base_flow_tex, GLuint beta_0_tex, GLuint smoothness_x_tex, GLuint smoothness_y_tex, GLuint equation_tex, int level_width, int level_height)
+void SetupEquations::exec(GLuint I_x_y_tex, GLuint I_t_tex, GLuint diff_flow_tex, GLuint base_flow_tex, GLuint beta_0_tex, GLuint diffusivity_tex, GLuint equation_red_tex, GLuint equation_black_tex, int level_width, int level_height, bool zero_diff_flow, int num_layers)
 {
        glUseProgram(equations_program);
 
@@ -789,71 +425,43 @@ void SetupEquations::exec(GLuint I_x_y_tex, GLuint I_t_tex, GLuint diff_flow_tex
        bind_sampler(equations_program, uniform_diff_flow_tex, 2, diff_flow_tex, nearest_sampler);
        bind_sampler(equations_program, uniform_base_flow_tex, 3, base_flow_tex, nearest_sampler);
        bind_sampler(equations_program, uniform_beta_0_tex, 4, beta_0_tex, nearest_sampler);
-       bind_sampler(equations_program, uniform_smoothness_x_tex, 5, smoothness_x_tex, zero_border_sampler);
-       bind_sampler(equations_program, uniform_smoothness_y_tex, 6, smoothness_y_tex, zero_border_sampler);
+       bind_sampler(equations_program, uniform_diffusivity_tex, 5, diffusivity_tex, zero_border_sampler);
        glProgramUniform1f(equations_program, uniform_delta, vr_delta);
        glProgramUniform1f(equations_program, uniform_gamma, vr_gamma);
+       glProgramUniform1i(equations_program, uniform_zero_diff_flow, zero_diff_flow);
 
-       glViewport(0, 0, level_width, level_height);
+       glViewport(0, 0, (level_width + 1) / 2, level_height);
        glDisable(GL_BLEND);
-       glBindVertexArray(equations_vao);
-       fbos.render_to(equation_tex);
-       glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+       fbos.render_to(equation_red_tex, equation_black_tex);
+       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, num_layers);
 }
 
-// Actually solve the equation sets made by SetupEquations, by means of
-// successive over-relaxation (SOR).
-//
-// See variational_refinement.txt for more information.
-class SOR {
-public:
-       SOR();
-       void exec(GLuint diff_flow_tex, GLuint equation_tex, GLuint smoothness_x_tex, GLuint smoothness_y_tex, int level_width, int level_height, int num_iterations);
-
-private:
-       PersistentFBOSet<1> fbos;
-
-       GLuint sor_vs_obj;
-       GLuint sor_fs_obj;
-       GLuint sor_program;
-       GLuint sor_vao;
-
-       GLuint uniform_diff_flow_tex;
-       GLuint uniform_equation_tex;
-       GLuint uniform_smoothness_x_tex, uniform_smoothness_y_tex;
-       GLuint uniform_phase;
-};
-
 SOR::SOR()
 {
-       sor_vs_obj = compile_shader(read_file("sor.vert"), GL_VERTEX_SHADER);
-       sor_fs_obj = compile_shader(read_file("sor.frag"), GL_FRAGMENT_SHADER);
+       sor_vs_obj = compile_shader(read_file("sor.vert", _binary_sor_vert_data, _binary_sor_vert_size), GL_VERTEX_SHADER);
+       sor_fs_obj = compile_shader(read_file("sor.frag", _binary_sor_frag_data, _binary_sor_frag_size), GL_FRAGMENT_SHADER);
        sor_program = link_program(sor_vs_obj, sor_fs_obj);
 
-       // Set up the VAO containing all the required position/texcoord data.
-       glCreateVertexArrays(1, &sor_vao);
-       glBindVertexArray(sor_vao);
-       glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
-
-       GLint position_attrib = glGetAttribLocation(sor_program, "position");
-       glEnableVertexArrayAttrib(sor_vao, position_attrib);
-       glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
-
        uniform_diff_flow_tex = glGetUniformLocation(sor_program, "diff_flow_tex");
-       uniform_equation_tex = glGetUniformLocation(sor_program, "equation_tex");
-       uniform_smoothness_x_tex = glGetUniformLocation(sor_program, "smoothness_x_tex");
-       uniform_smoothness_y_tex = glGetUniformLocation(sor_program, "smoothness_y_tex");
+       uniform_equation_red_tex = glGetUniformLocation(sor_program, "equation_red_tex");
+       uniform_equation_black_tex = glGetUniformLocation(sor_program, "equation_black_tex");
+       uniform_diffusivity_tex = glGetUniformLocation(sor_program, "diffusivity_tex");
        uniform_phase = glGetUniformLocation(sor_program, "phase");
+       uniform_num_nonzero_phases = glGetUniformLocation(sor_program, "num_nonzero_phases");
 }
 
-void SOR::exec(GLuint diff_flow_tex, GLuint equation_tex, GLuint smoothness_x_tex, GLuint smoothness_y_tex, int level_width, int level_height, int num_iterations)
+void SOR::exec(GLuint diff_flow_tex, GLuint equation_red_tex, GLuint equation_black_tex, GLuint diffusivity_tex, int level_width, int level_height, int num_iterations, bool zero_diff_flow, int num_layers, ScopedTimer *sor_timer)
 {
        glUseProgram(sor_program);
 
        bind_sampler(sor_program, uniform_diff_flow_tex, 0, diff_flow_tex, nearest_sampler);
-       bind_sampler(sor_program, uniform_smoothness_x_tex, 1, smoothness_x_tex, zero_border_sampler);
-       bind_sampler(sor_program, uniform_smoothness_y_tex, 2, smoothness_y_tex, zero_border_sampler);
-       bind_sampler(sor_program, uniform_equation_tex, 3, equation_tex, nearest_sampler);
+       bind_sampler(sor_program, uniform_diffusivity_tex, 1, diffusivity_tex, zero_border_sampler);
+       bind_sampler(sor_program, uniform_equation_red_tex, 2, equation_red_tex, nearest_sampler);
+       bind_sampler(sor_program, uniform_equation_black_tex, 3, equation_black_tex, nearest_sampler);
+
+       if (!zero_diff_flow) {
+               glProgramUniform1i(sor_program, uniform_num_nonzero_phases, 2);
+       }
 
        // NOTE: We bind to the texture we are rendering from, but we never write any value
        // that we read in the same shader pass (we call discard for red values when we compute
@@ -861,58 +469,45 @@ void SOR::exec(GLuint diff_flow_tex, GLuint equation_tex, GLuint smoothness_x_te
        // as per the spec.
        glViewport(0, 0, level_width, level_height);
        glDisable(GL_BLEND);
-       glBindVertexArray(sor_vao);
        fbos.render_to(diff_flow_tex);
 
        for (int i = 0; i < num_iterations; ++i) {
-               glProgramUniform1i(sor_program, uniform_phase, 0);
-               glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
-               glTextureBarrier();
-               glProgramUniform1i(sor_program, uniform_phase, 1);
-               glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
-               if (i != num_iterations - 1) {
+               {
+                       ScopedTimer timer("Red pass", sor_timer);
+                       if (zero_diff_flow && i == 0) {
+                               glProgramUniform1i(sor_program, uniform_num_nonzero_phases, 0);
+                       }
+                       glProgramUniform1i(sor_program, uniform_phase, 0);
+                       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, num_layers);
                        glTextureBarrier();
                }
+               {
+                       ScopedTimer timer("Black pass", sor_timer);
+                       if (zero_diff_flow && i == 0) {
+                               glProgramUniform1i(sor_program, uniform_num_nonzero_phases, 1);
+                       }
+                       glProgramUniform1i(sor_program, uniform_phase, 1);
+                       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, num_layers);
+                       if (zero_diff_flow && i == 0) {
+                               glProgramUniform1i(sor_program, uniform_num_nonzero_phases, 2);
+                       }
+                       if (i != num_iterations - 1) {
+                               glTextureBarrier();
+                       }
+               }
        }
 }
 
-// Simply add the differential flow found by the variational refinement to the base flow.
-// The output is in base_flow_tex; we don't need to make a new texture.
-class AddBaseFlow {
-public:
-       AddBaseFlow();
-       void exec(GLuint base_flow_tex, GLuint diff_flow_tex, int level_width, int level_height);
-
-private:
-       PersistentFBOSet<1> fbos;
-
-       GLuint add_flow_vs_obj;
-       GLuint add_flow_fs_obj;
-       GLuint add_flow_program;
-       GLuint add_flow_vao;
-
-       GLuint uniform_diff_flow_tex;
-};
-
 AddBaseFlow::AddBaseFlow()
 {
-       add_flow_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
-       add_flow_fs_obj = compile_shader(read_file("add_base_flow.frag"), GL_FRAGMENT_SHADER);
+       add_flow_vs_obj = compile_shader(read_file("vs.vert", _binary_vs_vert_data, _binary_vs_vert_size), GL_VERTEX_SHADER);
+       add_flow_fs_obj = compile_shader(read_file("add_base_flow.frag", _binary_add_base_flow_frag_data, _binary_add_base_flow_frag_size), GL_FRAGMENT_SHADER);
        add_flow_program = link_program(add_flow_vs_obj, add_flow_fs_obj);
 
-       // Set up the VAO containing all the required position/texcoord data.
-       glCreateVertexArrays(1, &add_flow_vao);
-       glBindVertexArray(add_flow_vao);
-       glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
-
-       GLint position_attrib = glGetAttribLocation(add_flow_program, "position");
-       glEnableVertexArrayAttrib(add_flow_vao, position_attrib);
-       glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
-
        uniform_diff_flow_tex = glGetUniformLocation(add_flow_program, "diff_flow_tex");
 }
 
-void AddBaseFlow::exec(GLuint base_flow_tex, GLuint diff_flow_tex, int level_width, int level_height)
+void AddBaseFlow::exec(GLuint base_flow_tex, GLuint diff_flow_tex, int level_width, int level_height, int num_layers)
 {
        glUseProgram(add_flow_program);
 
@@ -921,50 +516,22 @@ void AddBaseFlow::exec(GLuint base_flow_tex, GLuint diff_flow_tex, int level_wid
        glViewport(0, 0, level_width, level_height);
        glEnable(GL_BLEND);
        glBlendFunc(GL_ONE, GL_ONE);
-       glBindVertexArray(add_flow_vao);
        fbos.render_to(base_flow_tex);
 
-       glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, num_layers);
 }
 
-// Take a copy of the flow, bilinearly interpolated and scaled up.
-class ResizeFlow {
-public:
-       ResizeFlow();
-       void exec(GLuint in_tex, GLuint out_tex, int input_width, int input_height, int output_width, int output_height);
-
-private:
-       PersistentFBOSet<1> fbos;
-
-       GLuint resize_flow_vs_obj;
-       GLuint resize_flow_fs_obj;
-       GLuint resize_flow_program;
-       GLuint resize_flow_vao;
-
-       GLuint uniform_flow_tex;
-       GLuint uniform_scale_factor;
-};
-
 ResizeFlow::ResizeFlow()
 {
-       resize_flow_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
-       resize_flow_fs_obj = compile_shader(read_file("resize_flow.frag"), GL_FRAGMENT_SHADER);
+       resize_flow_vs_obj = compile_shader(read_file("vs.vert", _binary_vs_vert_data, _binary_vs_vert_size), GL_VERTEX_SHADER);
+       resize_flow_fs_obj = compile_shader(read_file("resize_flow.frag", _binary_resize_flow_frag_data, _binary_resize_flow_frag_size), GL_FRAGMENT_SHADER);
        resize_flow_program = link_program(resize_flow_vs_obj, resize_flow_fs_obj);
 
-       // Set up the VAO containing all the required position/texcoord data.
-       glCreateVertexArrays(1, &resize_flow_vao);
-       glBindVertexArray(resize_flow_vao);
-       glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
-
-       GLint position_attrib = glGetAttribLocation(resize_flow_program, "position");
-       glEnableVertexArrayAttrib(resize_flow_vao, position_attrib);
-       glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
-
        uniform_flow_tex = glGetUniformLocation(resize_flow_program, "flow_tex");
        uniform_scale_factor = glGetUniformLocation(resize_flow_program, "scale_factor");
 }
 
-void ResizeFlow::exec(GLuint flow_tex, GLuint out_tex, int input_width, int input_height, int output_width, int output_height)
+void ResizeFlow::exec(GLuint flow_tex, GLuint out_tex, int input_width, int input_height, int output_width, int output_height, int num_layers)
 {
        glUseProgram(resize_flow_program);
 
@@ -974,148 +541,13 @@ void ResizeFlow::exec(GLuint flow_tex, GLuint out_tex, int input_width, int inpu
 
        glViewport(0, 0, output_width, output_height);
        glDisable(GL_BLEND);
-       glBindVertexArray(resize_flow_vao);
        fbos.render_to(out_tex);
 
-       glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
-}
-
-class GPUTimers {
-public:
-       void print();
-       pair<GLuint, GLuint> begin_timer(const string &name, int level);
-
-private:
-       struct Timer {
-               string name;
-               int level;
-               pair<GLuint, GLuint> query;
-       };
-       vector<Timer> timers;
-};
-
-pair<GLuint, GLuint> GPUTimers::begin_timer(const string &name, int level)
-{
-       if (!enable_timing) {
-               return make_pair(0, 0);
-       }
-
-       GLuint queries[2];
-       glGenQueries(2, queries);
-       glQueryCounter(queries[0], GL_TIMESTAMP);
-
-       Timer timer;
-       timer.name = name;
-       timer.level = level;
-       timer.query.first = queries[0];
-       timer.query.second = queries[1];
-       timers.push_back(timer);
-       return timer.query;
+       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, num_layers);
 }
 
-void GPUTimers::print()
-{
-       for (const Timer &timer : timers) {
-               // NOTE: This makes the CPU wait for the GPU.
-               GLuint64 time_start, time_end;
-               glGetQueryObjectui64v(timer.query.first, GL_QUERY_RESULT, &time_start);
-               glGetQueryObjectui64v(timer.query.second, GL_QUERY_RESULT, &time_end);
-               //fprintf(stderr, "GPU time used = %.1f ms\n", time_elapsed / 1e6);
-               for (int i = 0; i < timer.level * 2; ++i) {
-                       fprintf(stderr, " ");
-               }
-               fprintf(stderr, "%-30s %4.1f ms\n", timer.name.c_str(), GLint64(time_end - time_start) / 1e6);
-       }
-}
-
-// A simple RAII class for timing until the end of the scope.
-class ScopedTimer {
-public:
-       ScopedTimer(const string &name, GPUTimers *timers)
-               : timers(timers), level(0)
-       {
-               query = timers->begin_timer(name, level);
-       }
-
-       ScopedTimer(const string &name, ScopedTimer *parent_timer)
-               : timers(parent_timer->timers),
-                 level(parent_timer->level + 1)
-       {
-               query = timers->begin_timer(name, level);
-       }
-
-       ~ScopedTimer()
-       {
-               end();
-       }
-
-       void end()
-       {
-               if (enable_timing && !ended) {
-                       glQueryCounter(query.second, GL_TIMESTAMP);
-                       ended = true;
-               }
-       }
-
-private:
-       GPUTimers *timers;
-       int level;
-       pair<GLuint, GLuint> query;
-       bool ended = false;
-};
-
-class TexturePool {
-public:
-       GLuint get_texture(GLenum format, GLuint width, GLuint height);
-       void release_texture(GLuint tex_num);
-
-private:
-       struct Texture {
-               GLuint tex_num;
-               GLenum format;
-               GLuint width, height;
-               bool in_use = false;
-       };
-       vector<Texture> textures;
-};
-
-class DISComputeFlow {
-public:
-       DISComputeFlow(int width, int height);
-
-       enum ResizeStrategy {
-               DO_NOT_RESIZE_FLOW,
-               RESIZE_FLOW_TO_FULL_SIZE
-       };
-
-       // Returns a texture that must be released with release_texture()
-       // after use.
-       GLuint exec(GLuint tex0, GLuint tex1, ResizeStrategy resize_strategy);
-
-       void release_texture(GLuint tex) {
-               pool.release_texture(tex);
-       }
-
-private:
-       int width, height;
-       GLuint initial_flow_tex;
-       TexturePool pool;
-
-       // The various passes.
-       Sobel sobel;
-       MotionSearch motion_search;
-       Densify densify;
-       Prewarp prewarp;
-       Derivatives derivatives;
-       ComputeSmoothness compute_smoothness;
-       SetupEquations setup_equations;
-       SOR sor;
-       AddBaseFlow add_base_flow;
-       ResizeFlow resize_flow;
-};
-
-DISComputeFlow::DISComputeFlow(int width, int height)
-       : width(width), height(height)
+DISComputeFlow::DISComputeFlow(int width, int height, const OperatingPoint &op)
+       : width(width), height(height), op(op), motion_search(op), densify(op)
 {
        // Make some samplers.
        glCreateSamplers(1, &nearest_sampler);
@@ -1135,35 +567,57 @@ DISComputeFlow::DISComputeFlow(int width, int height)
        // Similarly, gradients are zero outside the border, since the edge is taken
        // to be constant.
        glCreateSamplers(1, &zero_border_sampler);
-       glSamplerParameteri(zero_border_sampler, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
-       glSamplerParameteri(zero_border_sampler, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+       glSamplerParameteri(zero_border_sampler, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+       glSamplerParameteri(zero_border_sampler, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glSamplerParameteri(zero_border_sampler, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
        glSamplerParameteri(zero_border_sampler, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
-       float zero[] = { 0.0f, 0.0f, 0.0f, 0.0f };
+       float zero[] = { 0.0f, 0.0f, 0.0f, 0.0f };  // Note that zero alpha means we can also see whether we sampled outside the border or not.
        glSamplerParameterfv(zero_border_sampler, GL_TEXTURE_BORDER_COLOR, zero);
 
        // Initial flow is zero, 1x1.
-       glCreateTextures(GL_TEXTURE_2D, 1, &initial_flow_tex);
-       glTextureStorage2D(initial_flow_tex, 1, GL_RG16F, 1, 1);
+       glCreateTextures(GL_TEXTURE_2D_ARRAY, 1, &initial_flow_tex);
+       glTextureStorage3D(initial_flow_tex, 1, GL_RG16F, 1, 1, 1);
        glClearTexImage(initial_flow_tex, 0, GL_RG, GL_FLOAT, nullptr);
+
+       // Set up the vertex data that will be shared between all passes.
+       float vertices[] = {
+               0.0f, 1.0f,
+               0.0f, 0.0f,
+               1.0f, 1.0f,
+               1.0f, 0.0f,
+       };
+       glCreateBuffers(1, &vertex_vbo);
+       glNamedBufferData(vertex_vbo, sizeof(vertices), vertices, GL_STATIC_DRAW);
+
+       glCreateVertexArrays(1, &vao);
+       glBindVertexArray(vao);
+       glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
+
+       GLint position_attrib = 0;  // Hard-coded in every vertex shader.
+       glEnableVertexArrayAttrib(vao, position_attrib);
+       glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 }
 
-GLuint DISComputeFlow::exec(GLuint tex0, GLuint tex1, ResizeStrategy resize_strategy)
+GLuint DISComputeFlow::exec(GLuint tex, FlowDirection flow_direction, ResizeStrategy resize_strategy)
 {
+       int num_layers = (flow_direction == FORWARD_AND_BACKWARD) ? 2 : 1;
        int prev_level_width = 1, prev_level_height = 1;
        GLuint prev_level_flow_tex = initial_flow_tex;
 
        GPUTimers timers;
 
-       ScopedTimer total_timer("Total", &timers);
-       for (int level = coarsest_level; level >= int(finest_level); --level) {
+       glBindVertexArray(vao);
+       glDisable(GL_DITHER);
+
+       ScopedTimer total_timer("Compute flow", &timers);
+       for (int level = op.coarsest_level; level >= int(op.finest_level); --level) {
                char timer_name[256];
-               snprintf(timer_name, sizeof(timer_name), "Level %d", level);
+               snprintf(timer_name, sizeof(timer_name), "Level %d (%d x %d)", level, width >> level, height >> level);
                ScopedTimer level_timer(timer_name, &total_timer);
 
                int level_width = width >> level;
                int level_height = height >> level;
-               float patch_spacing_pixels = patch_size_pixels * (1.0f - patch_overlap_ratio);
+               float patch_spacing_pixels = op.patch_size_pixels * (1.0f - op.patch_overlap_ratio);
 
                // Make sure we have patches at least every Nth pixel, e.g. for width=9
                // and patch_spacing=3 (the default), we put out patch centers in
@@ -1175,45 +629,41 @@ GLuint DISComputeFlow::exec(GLuint tex0, GLuint tex1, ResizeStrategy resize_stra
                // Make sure we always read from the correct level; the chosen
                // mipmapping could otherwise be rather unpredictable, especially
                // during motion search.
-               GLuint tex0_view, tex1_view;
-               glGenTextures(1, &tex0_view);
-               glTextureView(tex0_view, GL_TEXTURE_2D, tex0, GL_R8, level, 1, 0, 1);
-               glGenTextures(1, &tex1_view);
-               glTextureView(tex1_view, GL_TEXTURE_2D, tex1, GL_R8, level, 1, 0, 1);
+               GLuint tex_view;
+               glGenTextures(1, &tex_view);
+               glTextureView(tex_view, GL_TEXTURE_2D_ARRAY, tex, GL_R8, level, 1, 0, 2);
 
-               // Create a new texture; we could be fancy and render use a multi-level
-               // texture, but meh.
-               GLuint grad0_tex = pool.get_texture(GL_RG16F, level_width, level_height);
+               // Create a new texture to hold the gradients.
+               GLuint grad_tex = pool.get_texture(GL_R32UI, level_width, level_height, num_layers);
 
                // Find the derivative.
                {
                        ScopedTimer timer("Sobel", &level_timer);
-                       sobel.exec(tex0_view, grad0_tex, level_width, level_height);
+                       sobel.exec(tex_view, grad_tex, level_width, level_height, num_layers);
                }
 
                // Motion search to find the initial flow. We use the flow from the previous
                // level (sampled bilinearly; no fancy tricks) as a guide, then search from there.
 
                // Create an output flow texture.
-               GLuint flow_out_tex = pool.get_texture(GL_RGB16F, width_patches, height_patches);
+               GLuint flow_out_tex = pool.get_texture(GL_RGB16F, width_patches, height_patches, num_layers);
 
                // And draw.
                {
                        ScopedTimer timer("Motion search", &level_timer);
-                       motion_search.exec(tex0_view, tex1_view, grad0_tex, prev_level_flow_tex, flow_out_tex, level_width, level_height, prev_level_width, prev_level_height, width_patches, height_patches);
+                       motion_search.exec(tex_view, grad_tex, prev_level_flow_tex, flow_out_tex, level_width, level_height, prev_level_width, prev_level_height, width_patches, height_patches, num_layers);
                }
-               pool.release_texture(grad0_tex);
+               pool.release_texture(grad_tex);
 
                // Densification.
 
-               // Set up an output texture (initially zero).
-               GLuint dense_flow_tex = pool.get_texture(GL_RGB16F, level_width, level_height);
-               glClearTexImage(dense_flow_tex, 0, GL_RGB, GL_FLOAT, nullptr);
+               // Set up an output texture (cleared in Densify).
+               GLuint dense_flow_tex = pool.get_texture(GL_RGB16F, level_width, level_height, num_layers);
 
                // And draw.
                {
                        ScopedTimer timer("Densification", &level_timer);
-                       densify.exec(tex0_view, tex1_view, flow_out_tex, dense_flow_tex, level_width, level_height, width_patches, height_patches);
+                       densify.exec(tex_view, flow_out_tex, dense_flow_tex, level_width, level_height, width_patches, height_patches, num_layers);
                }
                pool.release_texture(flow_out_tex);
 
@@ -1227,84 +677,82 @@ GLuint DISComputeFlow::exec(GLuint tex0, GLuint tex1, ResizeStrategy resize_stra
                // in pixels, not 0..1 normalized OpenGL texture coordinates.
                // This is because variational refinement depends so heavily on derivatives,
                // which are measured in intensity levels per pixel.
-               GLuint I_tex = pool.get_texture(GL_R16F, level_width, level_height);
-               GLuint I_t_tex = pool.get_texture(GL_R16F, level_width, level_height);
-               GLuint base_flow_tex = pool.get_texture(GL_RG16F, level_width, level_height);
+               GLuint I_tex = pool.get_texture(GL_R16F, level_width, level_height, num_layers);
+               GLuint I_t_tex = pool.get_texture(GL_R16F, level_width, level_height, num_layers);
+               GLuint base_flow_tex = pool.get_texture(GL_RG16F, level_width, level_height, num_layers);
                {
                        ScopedTimer timer("Prewarping", &varref_timer);
-                       prewarp.exec(tex0_view, tex1_view, dense_flow_tex, I_tex, I_t_tex, base_flow_tex, level_width, level_height);
+                       prewarp.exec(tex_view, dense_flow_tex, I_tex, I_t_tex, base_flow_tex, level_width, level_height, num_layers);
                }
                pool.release_texture(dense_flow_tex);
-               glDeleteTextures(1, &tex0_view);
-               glDeleteTextures(1, &tex1_view);
-
-               // Calculate I_x and I_y. We're only calculating first derivatives;
-               // the others will be taken on-the-fly in order to sample from fewer
-               // textures overall, since sampling from the L1 cache is cheap.
-               // (TODO: Verify that this is indeed faster than making separate
-               // double-derivative textures.)
-               GLuint I_x_y_tex = pool.get_texture(GL_RG16F, level_width, level_height);
-               GLuint beta_0_tex = pool.get_texture(GL_R16F, level_width, level_height);
-               {
-                       ScopedTimer timer("First derivatives", &varref_timer);
-                       derivatives.exec(I_tex, I_x_y_tex, beta_0_tex, level_width, level_height);
-               }
-               pool.release_texture(I_tex);
-
-               // We need somewhere to store du and dv (the flow increment, relative
-               // to the non-refined base flow u0 and v0). It starts at zero.
-               GLuint du_dv_tex = pool.get_texture(GL_RG16F, level_width, level_height);
-               glClearTexImage(du_dv_tex, 0, GL_RG, GL_FLOAT, nullptr);
-
-               // And for smoothness.
-               GLuint smoothness_x_tex = pool.get_texture(GL_R16F, level_width, level_height);
-               GLuint smoothness_y_tex = pool.get_texture(GL_R16F, level_width, level_height);
-
-               // And finally for the equation set. See SetupEquations for
-               // the storage format.
-               GLuint equation_tex = pool.get_texture(GL_RGBA32UI, level_width, level_height);
-
-               for (int outer_idx = 0; outer_idx < level + 1; ++outer_idx) {
-                       // Calculate the smoothness terms between the neighboring pixels,
-                       // both in x and y direction.
+               glDeleteTextures(1, &tex_view);
+
+               // TODO: If we don't have variational refinement, we don't need I and I_t,
+               // so computing them is a waste.
+               if (op.variational_refinement) {
+                       // Calculate I_x and I_y. We're only calculating first derivatives;
+                       // the others will be taken on-the-fly in order to sample from fewer
+                       // textures overall, since sampling from the L1 cache is cheap.
+                       // (TODO: Verify that this is indeed faster than making separate
+                       // double-derivative textures.)
+                       GLuint I_x_y_tex = pool.get_texture(GL_RG16F, level_width, level_height, num_layers);
+                       GLuint beta_0_tex = pool.get_texture(GL_R16F, level_width, level_height, num_layers);
                        {
-                               ScopedTimer timer("Compute smoothness", &varref_timer);
-                               compute_smoothness.exec(base_flow_tex, du_dv_tex, smoothness_x_tex, smoothness_y_tex, level_width, level_height);
+                               ScopedTimer timer("First derivatives", &varref_timer);
+                               derivatives.exec(I_tex, I_x_y_tex, beta_0_tex, level_width, level_height, num_layers);
                        }
-
-                       // Set up the 2x2 equation system for each pixel.
-                       {
-                               ScopedTimer timer("Set up equations", &varref_timer);
-                               setup_equations.exec(I_x_y_tex, I_t_tex, du_dv_tex, base_flow_tex, beta_0_tex, smoothness_x_tex, smoothness_y_tex, equation_tex, level_width, level_height);
+                       pool.release_texture(I_tex);
+
+                       // We need somewhere to store du and dv (the flow increment, relative
+                       // to the non-refined base flow u0 and v0). It's initially garbage,
+                       // but not read until we've written something sane to it.
+                       GLuint diff_flow_tex = pool.get_texture(GL_RG16F, level_width, level_height, num_layers);
+
+                       // And for diffusivity.
+                       GLuint diffusivity_tex = pool.get_texture(GL_R16F, level_width, level_height, num_layers);
+
+                       // And finally for the equation set. See SetupEquations for
+                       // the storage format.
+                       GLuint equation_red_tex = pool.get_texture(GL_RGBA32UI, (level_width + 1) / 2, level_height, num_layers);
+                       GLuint equation_black_tex = pool.get_texture(GL_RGBA32UI, (level_width + 1) / 2, level_height, num_layers);
+
+                       for (int outer_idx = 0; outer_idx < level + 1; ++outer_idx) {
+                               // Calculate the diffusivity term for each pixel.
+                               {
+                                       ScopedTimer timer("Compute diffusivity", &varref_timer);
+                                       compute_diffusivity.exec(base_flow_tex, diff_flow_tex, diffusivity_tex, level_width, level_height, outer_idx == 0, num_layers);
+                               }
+
+                               // Set up the 2x2 equation system for each pixel.
+                               {
+                                       ScopedTimer timer("Set up equations", &varref_timer);
+                                       setup_equations.exec(I_x_y_tex, I_t_tex, diff_flow_tex, base_flow_tex, beta_0_tex, diffusivity_tex, equation_red_tex, equation_black_tex, level_width, level_height, outer_idx == 0, num_layers);
+                               }
+
+                               // Run a few SOR iterations. Note that these are to/from the same texture.
+                               {
+                                       ScopedTimer timer("SOR", &varref_timer);
+                                       sor.exec(diff_flow_tex, equation_red_tex, equation_black_tex, diffusivity_tex, level_width, level_height, 5, outer_idx == 0, num_layers, &timer);
+                               }
                        }
 
-                       // Run a few SOR (or quasi-SOR, since we're not really Jacobi) iterations.
-                       // Note that these are to/from the same texture.
+                       pool.release_texture(I_t_tex);
+                       pool.release_texture(I_x_y_tex);
+                       pool.release_texture(beta_0_tex);
+                       pool.release_texture(diffusivity_tex);
+                       pool.release_texture(equation_red_tex);
+                       pool.release_texture(equation_black_tex);
+
+                       // Add the differential flow found by the variational refinement to the base flow,
+                       // giving the final flow estimate for this level.
+                       // The output is in base_flow_tex; we don't need to make a new texture.
                        {
-                               ScopedTimer timer("SOR", &varref_timer);
-                               sor.exec(du_dv_tex, equation_tex, smoothness_x_tex, smoothness_y_tex, level_width, level_height, 5);
+                               ScopedTimer timer("Add differential flow", &varref_timer);
+                               add_base_flow.exec(base_flow_tex, diff_flow_tex, level_width, level_height, num_layers);
                        }
+                       pool.release_texture(diff_flow_tex);
                }
 
-               pool.release_texture(I_t_tex);
-               pool.release_texture(I_x_y_tex);
-               pool.release_texture(beta_0_tex);
-               pool.release_texture(smoothness_x_tex);
-               pool.release_texture(smoothness_y_tex);
-               pool.release_texture(equation_tex);
-
-               // Add the differential flow found by the variational refinement to the base flow,
-               // giving the final flow estimate for this level.
-               // The output is in diff_flow_tex; we don't need to make a new texture.
-               //
-               // Disabling this doesn't save any time (although we could easily make it so that
-               // it is more efficient), but it helps debug the motion search.
-               if (enable_variational_refinement) {
-                       ScopedTimer timer("Add differential flow", &varref_timer);
-                       add_base_flow.exec(base_flow_tex, du_dv_tex, level_width, level_height);
-               }
-               pool.release_texture(du_dv_tex);
-
                if (prev_level_flow_tex != initial_flow_tex) {
                        pool.release_texture(prev_level_flow_tex);
                }
@@ -1314,581 +762,380 @@ GLuint DISComputeFlow::exec(GLuint tex0, GLuint tex1, ResizeStrategy resize_stra
        }
        total_timer.end();
 
-       timers.print();
+       if (!in_warmup) {
+               timers.print();
+       }
 
        // Scale up the flow to the final size (if needed).
-       if (finest_level == 0 || resize_strategy == DO_NOT_RESIZE_FLOW) {
+       if (op.finest_level == 0 || resize_strategy == DO_NOT_RESIZE_FLOW) {
                return prev_level_flow_tex;
        } else {
-               GLuint final_tex = pool.get_texture(GL_RG16F, width, height);
-               resize_flow.exec(prev_level_flow_tex, final_tex, prev_level_width, prev_level_height, width, height);
+               GLuint final_tex = pool.get_texture(GL_RG16F, width, height, num_layers);
+               resize_flow.exec(prev_level_flow_tex, final_tex, prev_level_width, prev_level_height, width, height, num_layers);
                pool.release_texture(prev_level_flow_tex);
                return final_tex;
        }
 }
 
-// Forward-warp the flow half-way (or rather, by alpha). A non-zero “splatting”
-// radius fills most of the holes.
-class Splat {
-public:
-       Splat();
-
-       // alpha is the time of the interpolated frame (0..1).
-       void exec(GLuint tex0, GLuint tex1, GLuint forward_flow_tex, GLuint backward_flow_tex, GLuint flow_tex, GLuint depth_tex, int width, int height, float alpha);
-
-private:
-       PersistentFBOSet<2> fbos;
-
-       GLuint splat_vs_obj;
-       GLuint splat_fs_obj;
-       GLuint splat_program;
-       GLuint splat_vao;
-
-       GLuint uniform_invert_flow, uniform_splat_size, uniform_alpha;
-       GLuint uniform_image0_tex, uniform_image1_tex, uniform_flow_tex;
-       GLuint uniform_inv_flow_size;
-};
-
-Splat::Splat()
+Splat::Splat(const OperatingPoint &op)
+       : op(op)
 {
-       splat_vs_obj = compile_shader(read_file("splat.vert"), GL_VERTEX_SHADER);
-       splat_fs_obj = compile_shader(read_file("splat.frag"), GL_FRAGMENT_SHADER);
+       splat_vs_obj = compile_shader(read_file("splat.vert", _binary_splat_vert_data, _binary_splat_vert_size), GL_VERTEX_SHADER);
+       splat_fs_obj = compile_shader(read_file("splat.frag", _binary_splat_frag_data, _binary_splat_frag_size), GL_FRAGMENT_SHADER);
        splat_program = link_program(splat_vs_obj, splat_fs_obj);
 
-       // Set up the VAO containing all the required position/texcoord data.
-       glCreateVertexArrays(1, &splat_vao);
-       glBindVertexArray(splat_vao);
-       glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
-
-       GLint position_attrib = glGetAttribLocation(splat_program, "position");
-       glEnableVertexArrayAttrib(splat_vao, position_attrib);
-       glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
-
-       uniform_invert_flow = glGetUniformLocation(splat_program, "invert_flow");
        uniform_splat_size = glGetUniformLocation(splat_program, "splat_size");
        uniform_alpha = glGetUniformLocation(splat_program, "alpha");
-       uniform_image0_tex = glGetUniformLocation(splat_program, "image0_tex");
-       uniform_image1_tex = glGetUniformLocation(splat_program, "image1_tex");
+       uniform_gray_tex = glGetUniformLocation(splat_program, "gray_tex");
        uniform_flow_tex = glGetUniformLocation(splat_program, "flow_tex");
        uniform_inv_flow_size = glGetUniformLocation(splat_program, "inv_flow_size");
 }
 
-void Splat::exec(GLuint tex0, GLuint tex1, GLuint forward_flow_tex, GLuint backward_flow_tex, GLuint flow_tex, GLuint depth_tex, int width, int height, float alpha)
+void Splat::exec(GLuint gray_tex, GLuint bidirectional_flow_tex, GLuint flow_tex, GLuint depth_rb, int width, int height, float alpha)
 {
        glUseProgram(splat_program);
 
-       bind_sampler(splat_program, uniform_image0_tex, 0, tex0, linear_sampler);
-       bind_sampler(splat_program, uniform_image1_tex, 1, tex1, linear_sampler);
+       bind_sampler(splat_program, uniform_gray_tex, 0, gray_tex, linear_sampler);
+       bind_sampler(splat_program, uniform_flow_tex, 1, bidirectional_flow_tex, nearest_sampler);
 
-       // FIXME: This is set to 1.0 right now so not to trigger Haswell's “PMA stall”.
-       // Move to 2.0 later.
-       float splat_size = 1.0f;  // 4x4 splat means 16x overdraw, 2x2 splat means 4x overdraw.
-       glProgramUniform2f(splat_program, uniform_splat_size, splat_size / width, splat_size / height);
+       glProgramUniform2f(splat_program, uniform_splat_size, op.splat_size / width, op.splat_size / height);
        glProgramUniform1f(splat_program, uniform_alpha, alpha);
        glProgramUniform2f(splat_program, uniform_inv_flow_size, 1.0f / width, 1.0f / height);
 
        glViewport(0, 0, width, height);
        glDisable(GL_BLEND);
        glEnable(GL_DEPTH_TEST);
+       glDepthMask(GL_TRUE);
        glDepthFunc(GL_LESS);  // We store the difference between I_0 and I_1, where less difference is good. (Default 1.0 is effectively +inf, which always loses.)
-       glBindVertexArray(splat_vao);
 
-       // FIXME: Get this into FBOSet, so we can reuse FBOs across frames.
-       GLuint fbo;
-       glCreateFramebuffers(1, &fbo);
-       glNamedFramebufferTexture(fbo, GL_COLOR_ATTACHMENT0, flow_tex, 0);
-       glNamedFramebufferTexture(fbo, GL_DEPTH_ATTACHMENT, depth_tex, 0);
-       glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+       fbos.render_to(depth_rb, flow_tex);
 
-       // Do forward splatting.
-       bind_sampler(splat_program, uniform_flow_tex, 2, forward_flow_tex, nearest_sampler);
-       glProgramUniform1i(splat_program, uniform_invert_flow, 0);
-       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, width * height);
+       // Evidently NVIDIA doesn't use fast clears for glClearTexImage, so clear now that
+       // we've got it bound.
+       glClearColor(1000.0f, 1000.0f, 0.0f, 1.0f);  // Invalid flow.
+       glClearDepth(1.0f);  // Effectively infinity.
+       glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 
-       // Do backward splatting.
-       bind_sampler(splat_program, uniform_flow_tex, 2, backward_flow_tex, nearest_sampler);
-       glProgramUniform1i(splat_program, uniform_invert_flow, 1);
-       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, width * height);
+       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, width * height * 2);
 
        glDisable(GL_DEPTH_TEST);
+}
 
-       glDeleteFramebuffers(1, &fbo);
+HoleFill::HoleFill()
+{
+       fill_vs_obj = compile_shader(read_file("hole_fill.vert", _binary_hole_fill_vert_data, _binary_hole_fill_vert_size), GL_VERTEX_SHADER);
+       fill_fs_obj = compile_shader(read_file("hole_fill.frag", _binary_hole_fill_frag_data, _binary_hole_fill_frag_size), GL_FRAGMENT_SHADER);
+       fill_program = link_program(fill_vs_obj, fill_fs_obj);
+
+       uniform_tex = glGetUniformLocation(fill_program, "tex");
+       uniform_z = glGetUniformLocation(fill_program, "z");
+       uniform_sample_offset = glGetUniformLocation(fill_program, "sample_offset");
 }
 
-class Blend {
-public:
-       Blend();
-       void exec(GLuint tex0, GLuint tex1, GLuint flow_tex, GLuint output_tex, int width, int height, float alpha);
+void HoleFill::exec(GLuint flow_tex, GLuint depth_rb, GLuint temp_tex[3], int width, int height)
+{
+       glUseProgram(fill_program);
 
-private:
-       PersistentFBOSet<1> fbos;
-       GLuint blend_vs_obj;
-       GLuint blend_fs_obj;
-       GLuint blend_program;
-       GLuint blend_vao;
+       bind_sampler(fill_program, uniform_tex, 0, flow_tex, nearest_sampler);
 
-       GLuint uniform_image0_tex, uniform_image1_tex, uniform_flow_tex;
-       GLuint uniform_alpha, uniform_flow_consistency_tolerance;
-};
+       glProgramUniform1f(fill_program, uniform_z, 1.0f - 1.0f / 1024.0f);
 
-Blend::Blend()
+       glViewport(0, 0, width, height);
+       glDisable(GL_BLEND);
+       glEnable(GL_DEPTH_TEST);
+       glDepthFunc(GL_LESS);  // Only update the values > 0.999f (ie., only invalid pixels).
+
+       fbos.render_to(depth_rb, flow_tex);  // NOTE: Reading and writing to the same texture.
+
+       // Fill holes from the left, by shifting 1, 2, 4, 8, etc. pixels to the right.
+       for (int offs = 1; offs < width; offs *= 2) {
+               glProgramUniform2f(fill_program, uniform_sample_offset, -offs / float(width), 0.0f);
+               glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+               glTextureBarrier();
+       }
+       glCopyImageSubData(flow_tex, GL_TEXTURE_2D, 0, 0, 0, 0, temp_tex[0], GL_TEXTURE_2D, 0, 0, 0, 0, width, height, 1);
+
+       // Similar to the right; adjust Z a bit down, so that we re-fill the pixels that
+       // were overwritten in the last algorithm.
+       glProgramUniform1f(fill_program, uniform_z, 1.0f - 2.0f / 1024.0f);
+       for (int offs = 1; offs < width; offs *= 2) {
+               glProgramUniform2f(fill_program, uniform_sample_offset, offs / float(width), 0.0f);
+               glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+               glTextureBarrier();
+       }
+       glCopyImageSubData(flow_tex, GL_TEXTURE_2D, 0, 0, 0, 0, temp_tex[1], GL_TEXTURE_2D, 0, 0, 0, 0, width, height, 1);
+
+       // Up.
+       glProgramUniform1f(fill_program, uniform_z, 1.0f - 3.0f / 1024.0f);
+       for (int offs = 1; offs < height; offs *= 2) {
+               glProgramUniform2f(fill_program, uniform_sample_offset, 0.0f, -offs / float(height));
+               glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+               glTextureBarrier();
+       }
+       glCopyImageSubData(flow_tex, GL_TEXTURE_2D, 0, 0, 0, 0, temp_tex[2], GL_TEXTURE_2D, 0, 0, 0, 0, width, height, 1);
+
+       // Down.
+       glProgramUniform1f(fill_program, uniform_z, 1.0f - 4.0f / 1024.0f);
+       for (int offs = 1; offs < height; offs *= 2) {
+               glProgramUniform2f(fill_program, uniform_sample_offset, 0.0f, offs / float(height));
+               glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+               glTextureBarrier();
+       }
+
+       glDisable(GL_DEPTH_TEST);
+}
+
+HoleBlend::HoleBlend()
 {
-       blend_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
-       blend_fs_obj = compile_shader(read_file("blend.frag"), GL_FRAGMENT_SHADER);
+       blend_vs_obj = compile_shader(read_file("hole_fill.vert", _binary_hole_fill_vert_data, _binary_hole_fill_vert_size), GL_VERTEX_SHADER);  // Reuse the vertex shader from the fill.
+       blend_fs_obj = compile_shader(read_file("hole_blend.frag", _binary_hole_blend_frag_data, _binary_hole_blend_frag_size), GL_FRAGMENT_SHADER);
        blend_program = link_program(blend_vs_obj, blend_fs_obj);
 
-       // Set up the VAO containing all the required position/texcoord data.
-       glCreateVertexArrays(1, &blend_vao);
-       glBindVertexArray(blend_vao);
+       uniform_left_tex = glGetUniformLocation(blend_program, "left_tex");
+       uniform_right_tex = glGetUniformLocation(blend_program, "right_tex");
+       uniform_up_tex = glGetUniformLocation(blend_program, "up_tex");
+       uniform_down_tex = glGetUniformLocation(blend_program, "down_tex");
+       uniform_z = glGetUniformLocation(blend_program, "z");
+       uniform_sample_offset = glGetUniformLocation(blend_program, "sample_offset");
+}
 
-       GLint position_attrib = glGetAttribLocation(blend_program, "position");
-       glEnableVertexArrayAttrib(blend_vao, position_attrib);
-       glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
+void HoleBlend::exec(GLuint flow_tex, GLuint depth_rb, GLuint temp_tex[3], int width, int height)
+{
+       glUseProgram(blend_program);
+
+       bind_sampler(blend_program, uniform_left_tex, 0, temp_tex[0], nearest_sampler);
+       bind_sampler(blend_program, uniform_right_tex, 1, temp_tex[1], nearest_sampler);
+       bind_sampler(blend_program, uniform_up_tex, 2, temp_tex[2], nearest_sampler);
+       bind_sampler(blend_program, uniform_down_tex, 3, flow_tex, nearest_sampler);
+
+       glProgramUniform1f(blend_program, uniform_z, 1.0f - 4.0f / 1024.0f);
+       glProgramUniform2f(blend_program, uniform_sample_offset, 0.0f, 0.0f);
+
+       glViewport(0, 0, width, height);
+       glDisable(GL_BLEND);
+       glEnable(GL_DEPTH_TEST);
+       glDepthFunc(GL_LEQUAL);  // Skip over all of the pixels that were never holes to begin with.
+
+       fbos.render_to(depth_rb, flow_tex);  // NOTE: Reading and writing to the same texture.
+
+       glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+
+       glDisable(GL_DEPTH_TEST);
+}
+
+Blend::Blend(bool split_ycbcr_output)
+       : split_ycbcr_output(split_ycbcr_output)
+{
+       string frag_shader = read_file("blend.frag", _binary_blend_frag_data, _binary_blend_frag_size);
+       if (split_ycbcr_output) {
+               // Insert after the first #version line.
+               size_t offset = frag_shader.find('\n');
+               assert(offset != string::npos);
+               frag_shader = frag_shader.substr(0, offset + 1) + "#define SPLIT_YCBCR_OUTPUT 1\n" + frag_shader.substr(offset + 1);
+       }
 
-       uniform_image0_tex = glGetUniformLocation(blend_program, "image0_tex");
-       uniform_image1_tex = glGetUniformLocation(blend_program, "image1_tex");
+       blend_vs_obj = compile_shader(read_file("vs.vert", _binary_vs_vert_data, _binary_vs_vert_size), GL_VERTEX_SHADER);
+       blend_fs_obj = compile_shader(frag_shader, GL_FRAGMENT_SHADER);
+       blend_program = link_program(blend_vs_obj, blend_fs_obj);
+
+       uniform_image_tex = glGetUniformLocation(blend_program, "image_tex");
        uniform_flow_tex = glGetUniformLocation(blend_program, "flow_tex");
        uniform_alpha = glGetUniformLocation(blend_program, "alpha");
        uniform_flow_consistency_tolerance = glGetUniformLocation(blend_program, "flow_consistency_tolerance");
 }
 
-void Blend::exec(GLuint tex0, GLuint tex1, GLuint flow_tex, GLuint output_tex, int level_width, int level_height, float alpha)
+void Blend::exec(GLuint image_tex, GLuint flow_tex, GLuint output_tex, GLuint output2_tex, int level_width, int level_height, float alpha)
 {
        glUseProgram(blend_program);
-       bind_sampler(blend_program, uniform_image0_tex, 0, tex0, linear_sampler);
-       bind_sampler(blend_program, uniform_image1_tex, 1, tex1, linear_sampler);
-       bind_sampler(blend_program, uniform_flow_tex, 2, flow_tex, linear_sampler);  // May be upsampled.
+       bind_sampler(blend_program, uniform_image_tex, 0, image_tex, linear_sampler);
+       bind_sampler(blend_program, uniform_flow_tex, 1, flow_tex, linear_sampler);  // May be upsampled.
        glProgramUniform1f(blend_program, uniform_alpha, alpha);
-       //glProgramUniform1f(blend_program, uniform_flow_consistency_tolerance, 1.0f / 
 
        glViewport(0, 0, level_width, level_height);
-       fbos.render_to(output_tex);
-       glBindVertexArray(blend_vao);
-       glUseProgram(blend_program);
+       if (split_ycbcr_output) {
+               fbos_split.render_to(output_tex, output2_tex);
+       } else {
+               fbos.render_to(output_tex);
+       }
        glDisable(GL_BLEND);  // A bit ironic, perhaps.
        glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 }
 
-class Interpolate {
-public:
-       Interpolate(int width, int height, int flow_level);
-
-       // Returns a texture that must be released with release_texture()
-       // after use. tex0 and tex1 must be RGBA8 textures with mipmaps
-       // (unless flow_level == 0).
-       GLuint exec(GLuint tex0, GLuint tex1, GLuint forward_flow_tex, GLuint backward_flow_tex, GLuint width, GLuint height, float alpha);
-
-       void release_texture(GLuint tex) {
-               pool.release_texture(tex);
-       }
+Interpolate::Interpolate(const OperatingPoint &op, bool split_ycbcr_output)
+       : flow_level(op.finest_level),
+         split_ycbcr_output(split_ycbcr_output),
+         splat(op),
+         blend(split_ycbcr_output) {
+       // Set up the vertex data that will be shared between all passes.
+       float vertices[] = {
+               0.0f, 1.0f,
+               0.0f, 0.0f,
+               1.0f, 1.0f,
+               1.0f, 0.0f,
+       };
+       glCreateBuffers(1, &vertex_vbo);
+       glNamedBufferData(vertex_vbo, sizeof(vertices), vertices, GL_STATIC_DRAW);
 
-private:
-       int width, height, flow_level;
-       TexturePool pool;
-       Splat splat;
-       Blend blend;
-};
+       glCreateVertexArrays(1, &vao);
+       glBindVertexArray(vao);
+       glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 
-Interpolate::Interpolate(int width, int height, int flow_level)
-       : width(width), height(height), flow_level(flow_level) {}
+       GLint position_attrib = 0;  // Hard-coded in every vertex shader.
+       glEnableVertexArrayAttrib(vao, position_attrib);
+       glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
+}
 
-GLuint Interpolate::exec(GLuint tex0, GLuint tex1, GLuint forward_flow_tex, GLuint backward_flow_tex, GLuint width, GLuint height, float alpha)
+pair<GLuint, GLuint> Interpolate::exec(GLuint image_tex, GLuint gray_tex, GLuint bidirectional_flow_tex, GLuint width, GLuint height, float alpha)
 {
        GPUTimers timers;
 
-       ScopedTimer total_timer("Total", &timers);
+       ScopedTimer total_timer("Interpolate", &timers);
+
+       glBindVertexArray(vao);
+       glDisable(GL_DITHER);
 
        // Pick out the right level to test splatting results on.
-       GLuint tex0_view, tex1_view;
-       glGenTextures(1, &tex0_view);
-       glTextureView(tex0_view, GL_TEXTURE_2D, tex0, GL_RGBA8, flow_level, 1, 0, 1);
-       glGenTextures(1, &tex1_view);
-       glTextureView(tex1_view, GL_TEXTURE_2D, tex1, GL_RGBA8, flow_level, 1, 0, 1);
+       GLuint tex_view;
+       glGenTextures(1, &tex_view);
+       glTextureView(tex_view, GL_TEXTURE_2D_ARRAY, gray_tex, GL_R8, flow_level, 1, 0, 2);
 
        int flow_width = width >> flow_level;
        int flow_height = height >> flow_level;
 
        GLuint flow_tex = pool.get_texture(GL_RG16F, flow_width, flow_height);
-       GLuint depth_tex = pool.get_texture(GL_DEPTH_COMPONENT32F, flow_width, flow_height);  // Used for ranking flows.
-       {
-               ScopedTimer timer("Clear", &total_timer);
-               glClearTexImage(flow_tex, 0, GL_RG, GL_FLOAT, nullptr);
-               float infinity = 1.0f;
-               glClearTexImage(depth_tex, 0, GL_DEPTH_COMPONENT, GL_FLOAT, &infinity);
-       }
+       GLuint depth_rb = pool.get_renderbuffer(GL_DEPTH_COMPONENT16, flow_width, flow_height);  // Used for ranking flows.
 
-       //SDL_GL_SwapWindow(window);
        {
                ScopedTimer timer("Splat", &total_timer);
-               splat.exec(tex0_view, tex1_view, forward_flow_tex, backward_flow_tex, flow_tex, depth_tex, flow_width, flow_height, alpha);
+               splat.exec(tex_view, bidirectional_flow_tex, flow_tex, depth_rb, flow_width, flow_height, alpha);
        }
-       //SDL_GL_SwapWindow(window);
-       pool.release_texture(depth_tex);
-       glDeleteTextures(1, &tex0_view);
-       glDeleteTextures(1, &tex1_view);
+       glDeleteTextures(1, &tex_view);
+
+       GLuint temp_tex[3];
+       temp_tex[0] = pool.get_texture(GL_RG16F, flow_width, flow_height);
+       temp_tex[1] = pool.get_texture(GL_RG16F, flow_width, flow_height);
+       temp_tex[2] = pool.get_texture(GL_RG16F, flow_width, flow_height);
 
-       GLuint output_tex = pool.get_texture(GL_RGB8, width, height);
        {
-               ScopedTimer timer("Blend", &total_timer);
-               blend.exec(tex0, tex1, flow_tex, output_tex, width, height, alpha);
+               ScopedTimer timer("Fill holes", &total_timer);
+               hole_fill.exec(flow_tex, depth_rb, temp_tex, flow_width, flow_height);
+               hole_blend.exec(flow_tex, depth_rb, temp_tex, flow_width, flow_height);
        }
-       total_timer.end();
-       timers.print();
 
-       return output_tex;
-}
+       pool.release_texture(temp_tex[0]);
+       pool.release_texture(temp_tex[1]);
+       pool.release_texture(temp_tex[2]);
+       pool.release_renderbuffer(depth_rb);
 
-GLuint TexturePool::get_texture(GLenum format, GLuint width, GLuint height)
-{
-       for (Texture &tex : textures) {
-               if (!tex.in_use && tex.format == format &&
-                   tex.width == width && tex.height == height) {
-                       tex.in_use = true;
-                       return tex.tex_num;
+       GLuint output_tex, output2_tex = 0;
+       if (split_ycbcr_output) {
+               output_tex = pool.get_texture(GL_R8, width, height);
+               output2_tex = pool.get_texture(GL_RG8, width, height);
+               {
+                       ScopedTimer timer("Blend", &total_timer);
+                       blend.exec(image_tex, flow_tex, output_tex, output2_tex, width, height, alpha);
                }
-       }
-
-       Texture tex;
-       glCreateTextures(GL_TEXTURE_2D, 1, &tex.tex_num);
-       glTextureStorage2D(tex.tex_num, 1, format, width, height);
-       tex.format = format;
-       tex.width = width;
-       tex.height = height;
-       tex.in_use = true;
-       textures.push_back(tex);
-       return tex.tex_num;
-}
-
-void TexturePool::release_texture(GLuint tex_num)
-{
-       for (Texture &tex : textures) {
-               if (tex.tex_num == tex_num) {
-                       assert(tex.in_use);
-                       tex.in_use = false;
-                       return;
+       } else {
+               output_tex = pool.get_texture(GL_RGBA8, width, height);
+               {
+                       ScopedTimer timer("Blend", &total_timer);
+                       blend.exec(image_tex, flow_tex, output_tex, 0, width, height, alpha);
                }
        }
-       assert(false);
-}
-
-// OpenGL uses a bottom-left coordinate system, .flo files use a top-left coordinate system.
-void flip_coordinate_system(float *dense_flow, unsigned width, unsigned height)
-{
-       for (unsigned i = 0; i < width * height; ++i) {
-               dense_flow[i * 2 + 1] = -dense_flow[i * 2 + 1];
+       pool.release_texture(flow_tex);
+       total_timer.end();
+       if (!in_warmup) {
+               timers.print();
        }
-}
 
-void write_flow(const char *filename, const float *dense_flow, unsigned width, unsigned height)
-{
-       FILE *flowfp = fopen(filename, "wb");
-       fprintf(flowfp, "FEIH");
-       fwrite(&width, 4, 1, flowfp);
-       fwrite(&height, 4, 1, flowfp);
-       for (unsigned y = 0; y < height; ++y) {
-               int yy = height - y - 1;
-               fwrite(&dense_flow[yy * width * 2], width * 2 * sizeof(float), 1, flowfp);
-       }
-       fclose(flowfp);
+       return make_pair(output_tex, output2_tex);
 }
 
-void write_ppm(const char *filename, const float *dense_flow, unsigned width, unsigned height)
+GLuint TexturePool::get_texture(GLenum format, GLuint width, GLuint height, GLuint num_layers)
 {
-       FILE *fp = fopen(filename, "wb");
-       fprintf(fp, "P6\n%d %d\n255\n", width, height);
-       for (unsigned y = 0; y < unsigned(height); ++y) {
-               int yy = height - y - 1;
-               for (unsigned x = 0; x < unsigned(width); ++x) {
-                       float du = dense_flow[(yy * width + x) * 2 + 0];
-                       float dv = dense_flow[(yy * width + x) * 2 + 1];
-
-                       uint8_t r, g, b;
-                       flow2rgb(du, dv, &r, &g, &b);
-                       putc(r, fp);
-                       putc(g, fp);
-                       putc(b, fp);
+       {
+               lock_guard<mutex> lock(mu);
+               for (Texture &tex : textures) {
+                       if (!tex.in_use && !tex.is_renderbuffer && tex.format == format &&
+                           tex.width == width && tex.height == height && tex.num_layers == num_layers) {
+                               tex.in_use = true;
+                               return tex.tex_num;
+                       }
                }
        }
-       fclose(fp);
-}
 
-void finish_one_read(GLuint width, GLuint height)
-{
-       assert(!reads_in_progress.empty());
-       ReadInProgress read = reads_in_progress.front();
-       reads_in_progress.pop_front();
-
-       unique_ptr<float[]> flow(new float[width * height * 2]);
-       void *buf = glMapNamedBufferRange(read.pbo, 0, width * height * 2 * sizeof(float), GL_MAP_READ_BIT);  // Blocks if the read isn't done yet.
-       memcpy(flow.get(), buf, width * height * 2 * sizeof(float));
-       glUnmapNamedBuffer(read.pbo);
-       spare_pbos.push(read.pbo);
-
-       flip_coordinate_system(flow.get(), width, height);
-       if (!read.flow_filename.empty()) {
-               write_flow(read.flow_filename.c_str(), flow.get(), width, height);
-               fprintf(stderr, "%s %s -> %s\n", read.filename0.c_str(), read.filename1.c_str(), read.flow_filename.c_str());
-       }
-       if (!read.ppm_filename.empty()) {
-               write_ppm(read.ppm_filename.c_str(), flow.get(), width, height);
+       Texture tex;
+       if (num_layers == 0) {
+               glCreateTextures(GL_TEXTURE_2D, 1, &tex.tex_num);
+               glTextureStorage2D(tex.tex_num, 1, format, width, height);
+       } else {
+               glCreateTextures(GL_TEXTURE_2D_ARRAY, 1, &tex.tex_num);
+               glTextureStorage3D(tex.tex_num, 1, format, width, height, num_layers);
        }
-}
-
-void schedule_read(GLuint tex, GLuint width, GLuint height, const char *filename0, const char *filename1, const char *flow_filename, const char *ppm_filename)
-{
-       if (spare_pbos.empty()) {
-               finish_one_read(width, height);
+       tex.format = format;
+       tex.width = width;
+       tex.height = height;
+       tex.num_layers = num_layers;
+       tex.in_use = true;
+       tex.is_renderbuffer = false;
+       {
+               lock_guard<mutex> lock(mu);
+               textures.push_back(tex);
        }
-       assert(!spare_pbos.empty());
-       reads_in_progress.emplace_back(ReadInProgress{ spare_pbos.top(), filename0, filename1, flow_filename, ppm_filename });
-       glBindBuffer(GL_PIXEL_PACK_BUFFER, spare_pbos.top());
-       spare_pbos.pop();
-       glGetTextureImage(tex, 0, GL_RG, GL_FLOAT, width * height * 2 * sizeof(float), nullptr);
-       glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);
+       return tex.tex_num;
 }
 
-void compute_flow_only(int argc, char **argv, int optind)
+GLuint TexturePool::get_renderbuffer(GLenum format, GLuint width, GLuint height)
 {
-       const char *filename0 = argc >= (optind + 1) ? argv[optind] : "test1499.png";
-       const char *filename1 = argc >= (optind + 2) ? argv[optind + 1] : "test1500.png";
-       const char *flow_filename = argc >= (optind + 3) ? argv[optind + 2] : "flow.flo";
-
-       // Load pictures.
-       unsigned width1, height1, width2, height2;
-       GLuint tex0 = load_texture(filename0, &width1, &height1, WITHOUT_MIPMAPS);
-       GLuint tex1 = load_texture(filename1, &width2, &height2, WITHOUT_MIPMAPS);
-
-       if (width1 != width2 || height1 != height2) {
-               fprintf(stderr, "Image dimensions don't match (%dx%d versus %dx%d)\n",
-                       width1, height1, width2, height2);
-               exit(1);
-       }
-
-       // Set up some PBOs to do asynchronous readback.
-       GLuint pbos[5];
-       glCreateBuffers(5, pbos);
-       for (int i = 0; i < 5; ++i) {
-               glNamedBufferData(pbos[i], width1 * height1 * 2 * sizeof(float), nullptr, GL_STREAM_READ);
-               spare_pbos.push(pbos[i]);
-       }
-
-       int levels = find_num_levels(width1, height1);
-       GLuint tex0_gray, tex1_gray;
-       glCreateTextures(GL_TEXTURE_2D, 1, &tex0_gray);
-       glCreateTextures(GL_TEXTURE_2D, 1, &tex1_gray);
-       glTextureStorage2D(tex0_gray, levels, GL_R8, width1, height1);
-       glTextureStorage2D(tex1_gray, levels, GL_R8, width1, height1);
-
-       GrayscaleConversion gray;
-       gray.exec(tex0, tex0_gray, width1, height1);
-       glDeleteTextures(1, &tex0);
-       glGenerateTextureMipmap(tex0_gray);
-
-       gray.exec(tex1, tex1_gray, width1, height1);
-       glDeleteTextures(1, &tex1);
-       glGenerateTextureMipmap(tex1_gray);
-
-       DISComputeFlow compute_flow(width1, height1);
-       GLuint final_tex = compute_flow.exec(tex0_gray, tex1_gray, DISComputeFlow::RESIZE_FLOW_TO_FULL_SIZE);
-
-       schedule_read(final_tex, width1, height1, filename0, filename1, flow_filename, "flow.ppm");
-       compute_flow.release_texture(final_tex);
-
-       // See if there are more flows on the command line (ie., more than three arguments),
-       // and if so, process them.
-       int num_flows = (argc - optind) / 3;
-       for (int i = 1; i < num_flows; ++i) {
-               const char *filename0 = argv[optind + i * 3 + 0];
-               const char *filename1 = argv[optind + i * 3 + 1];
-               const char *flow_filename = argv[optind + i * 3 + 2];
-               GLuint width, height;
-               GLuint tex0 = load_texture(filename0, &width, &height, WITHOUT_MIPMAPS);
-               if (width != width1 || height != height1) {
-                       fprintf(stderr, "%s: Image dimensions don't match (%dx%d versus %dx%d)\n",
-                               filename0, width, height, width1, height1);
-                       exit(1);
-               }
-               gray.exec(tex0, tex0_gray, width, height);
-               glGenerateTextureMipmap(tex0_gray);
-               glDeleteTextures(1, &tex0);
-
-               GLuint tex1 = load_texture(filename1, &width, &height, WITHOUT_MIPMAPS);
-               if (width != width1 || height != height1) {
-                       fprintf(stderr, "%s: Image dimensions don't match (%dx%d versus %dx%d)\n",
-                               filename1, width, height, width1, height1);
-                       exit(1);
+       {
+               lock_guard<mutex> lock(mu);
+               for (Texture &tex : textures) {
+                       if (!tex.in_use && tex.is_renderbuffer && tex.format == format &&
+                           tex.width == width && tex.height == height) {
+                               tex.in_use = true;
+                               return tex.tex_num;
+                       }
                }
-               gray.exec(tex1, tex1_gray, width, height);
-               glGenerateTextureMipmap(tex1_gray);
-               glDeleteTextures(1, &tex1);
-
-               GLuint final_tex = compute_flow.exec(tex0_gray, tex1_gray, DISComputeFlow::RESIZE_FLOW_TO_FULL_SIZE);
-
-               schedule_read(final_tex, width1, height1, filename0, filename1, flow_filename, "");
-               compute_flow.release_texture(final_tex);
        }
-       glDeleteTextures(1, &tex0_gray);
-       glDeleteTextures(1, &tex1_gray);
 
-       while (!reads_in_progress.empty()) {
-               finish_one_read(width1, height1);
+       Texture tex;
+       glCreateRenderbuffers(1, &tex.tex_num);
+       glNamedRenderbufferStorage(tex.tex_num, format, width, height);
+
+       tex.format = format;
+       tex.width = width;
+       tex.height = height;
+       tex.in_use = true;
+       tex.is_renderbuffer = true;
+       {
+               lock_guard<mutex> lock(mu);
+               textures.push_back(tex);
        }
+       return tex.tex_num;
 }
 
-// Interpolate images based on
-//
-//   Herbst, Seitz, Baker: “Occlusion Reasoning for Temporal Interpolation
-//   Using Optical Flow”
-//
-// or at least a reasonable subset thereof. Unfinished.
-void interpolate_image(int argc, char **argv, int optind)
+void TexturePool::release_texture(GLuint tex_num)
 {
-       const char *filename0 = argc >= (optind + 1) ? argv[optind] : "test1499.png";
-       const char *filename1 = argc >= (optind + 2) ? argv[optind + 1] : "test1500.png";
-       //const char *out_filename = argc >= (optind + 3) ? argv[optind + 2] : "interpolated.png";
-
-       // Load pictures.
-       unsigned width1, height1, width2, height2;
-       GLuint tex0 = load_texture(filename0, &width1, &height1, WITH_MIPMAPS);
-       GLuint tex1 = load_texture(filename1, &width2, &height2, WITH_MIPMAPS);
-
-       if (width1 != width2 || height1 != height2) {
-               fprintf(stderr, "Image dimensions don't match (%dx%d versus %dx%d)\n",
-                       width1, height1, width2, height2);
-               exit(1);
-       }
-
-       // Set up some PBOs to do asynchronous readback.
-       GLuint pbos[5];
-       glCreateBuffers(5, pbos);
-       for (int i = 0; i < 5; ++i) {
-               glNamedBufferData(pbos[i], width1 * height1 * 2 * sizeof(float), nullptr, GL_STREAM_READ);
-               spare_pbos.push(pbos[i]);
-       }
-
-       DISComputeFlow compute_flow(width1, height1);
-       GrayscaleConversion gray;
-       Interpolate interpolate(width1, height1, finest_level);
-       //Interpolate interpolate(width1, height1, 0);
-
-       int levels = find_num_levels(width1, height1);
-       GLuint tex0_gray, tex1_gray;
-       glCreateTextures(GL_TEXTURE_2D, 1, &tex0_gray);
-       glCreateTextures(GL_TEXTURE_2D, 1, &tex1_gray);
-       glTextureStorage2D(tex0_gray, levels, GL_R8, width1, height1);
-       glTextureStorage2D(tex1_gray, levels, GL_R8, width1, height1);
-
-       gray.exec(tex0, tex0_gray, width1, height1);
-       glGenerateTextureMipmap(tex0_gray);
-
-       gray.exec(tex1, tex1_gray, width1, height1);
-       glGenerateTextureMipmap(tex1_gray);
-
-       GLuint forward_flow_tex = compute_flow.exec(tex0_gray, tex1_gray, DISComputeFlow::DO_NOT_RESIZE_FLOW);
-       GLuint backward_flow_tex = compute_flow.exec(tex1_gray, tex0_gray, DISComputeFlow::DO_NOT_RESIZE_FLOW);
-
-       for (int frameno = 1; frameno < 60; ++frameno) {
-               float alpha = frameno / 60.0f;
-               GLuint interpolated_tex = interpolate.exec(tex0, tex1, forward_flow_tex, backward_flow_tex, width1, height1, alpha);
-
-               unique_ptr<uint8_t[]> rgb(new uint8_t[width1 * height1 * 3]);
-               glGetTextureImage(interpolated_tex, 0, GL_RGB, GL_UNSIGNED_BYTE, width1 * height1 * 3, rgb.get());
-
-               char buf[256];
-               snprintf(buf, sizeof(buf), "interp%04d.ppm", frameno);
-               FILE *fp = fopen(buf, "wb");
-               fprintf(fp, "P6\n%d %d\n255\n", width1, height1);
-               for (unsigned y = 0; y < height1; ++y) {
-                       unsigned y2 = height1 - 1 - y;
-                       fwrite(rgb.get() + y2 * width1 * 3, width1 * 3, 1, fp);
+       lock_guard<mutex> lock(mu);
+       for (Texture &tex : textures) {
+               if (!tex.is_renderbuffer && tex.tex_num == tex_num) {
+                       assert(tex.in_use);
+                       tex.in_use = false;
+                       return;
                }
-               fclose(fp);
        }
-
-       //schedule_read(interpolated_tex, width1, height1, filename0, filename1, "", "halfflow.ppm");
-       //interpolate.release_texture(interpolated_tex);
-       //finish_one_read(width1, height1);
+       assert(false);
 }
 
-int main(int argc, char **argv)
+void TexturePool::release_renderbuffer(GLuint tex_num)
 {
-        static const option long_options[] = {
-               { "smoothness-relative-weight", required_argument, 0, 's' },  // alpha.
-               { "intensity-relative-weight", required_argument, 0, 'i' },  // delta.
-               { "gradient-relative-weight", required_argument, 0, 'g' },  // gamma.
-               { "disable-timing", no_argument, 0, 1000 },
-               { "ignore-variational-refinement", no_argument, 0, 1001 },  // Still calculates it, just doesn't apply it.
-               { "interpolate", no_argument, 0, 1002 }
-       };
-
-       for ( ;; ) {
-               int option_index = 0;
-               int c = getopt_long(argc, argv, "s:i:g:", long_options, &option_index);
-
-               if (c == -1) {
-                       break;
+       lock_guard<mutex> lock(mu);
+       for (Texture &tex : textures) {
+               if (tex.is_renderbuffer && tex.tex_num == tex_num) {
+                       assert(tex.in_use);
+                       tex.in_use = false;
+                       return;
                }
-               switch (c) {
-               case 's':
-                       vr_alpha = atof(optarg);
-                       break;
-               case 'i':
-                       vr_delta = atof(optarg);
-                       break;
-               case 'g':
-                       vr_gamma = atof(optarg);
-                       break;
-               case 1000:
-                       enable_timing = false;
-                       break;
-               case 1001:
-                       enable_variational_refinement = false;
-                       break;
-               case 1002:
-                       enable_interpolation = true;
-                       break;
-               default:
-                       fprintf(stderr, "Unknown option '%s'\n", argv[option_index]);
-                       exit(1);
-               };
-       }
-
-       if (SDL_Init(SDL_INIT_EVERYTHING) == -1) {
-               fprintf(stderr, "SDL_Init failed: %s\n", SDL_GetError());
-               exit(1);
-       }
-       SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);
-       SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 0);
-       SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 0);
-       SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
-
-       SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
-       SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4);
-       SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 5);
-       // SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_DEBUG_FLAG);
-       window = SDL_CreateWindow("OpenGL window",
-               SDL_WINDOWPOS_UNDEFINED,
-               SDL_WINDOWPOS_UNDEFINED,
-               64, 64,
-               SDL_WINDOW_OPENGL | SDL_WINDOW_HIDDEN);
-       SDL_GLContext context = SDL_GL_CreateContext(window);
-       assert(context != nullptr);
-
-       // FIXME: Should be part of DISComputeFlow (but needs to be initialized
-       // before all the render passes).
-       float vertices[] = {
-               0.0f, 1.0f,
-               0.0f, 0.0f,
-               1.0f, 1.0f,
-               1.0f, 0.0f,
-       };
-       glCreateBuffers(1, &vertex_vbo);
-       glNamedBufferData(vertex_vbo, sizeof(vertices), vertices, GL_STATIC_DRAW);
-       glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
-
-       if (enable_interpolation) {
-               interpolate_image(argc, argv, optind);
-       } else {
-               compute_flow_only(argc, argv, optind);
        }
+       //assert(false);
 }