#include <stdio.h>
#include <unistd.h>
+#include "flow.h"
#include "gpu_timers.h"
#include "util.h"
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) {
- render_to({{texture0}});
- }
-
- void render_to(GLuint texture0, GLuint texture1) {
- render_to({{texture0, texture1}});
- }
-
- void render_to(GLuint texture0, GLuint texture1, GLuint texture2) {
- render_to({{texture0, texture1, texture2}});
- }
-
- void render_to(GLuint texture0, GLuint texture1, GLuint texture2, GLuint texture3) {
- 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)
{
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
}
-// Same, but with a depth texture.
-template<size_t num_elements>
-class PersistentFBOSetWithDepth {
-public:
- void render_to(GLuint depth_rb, const array<GLuint, num_elements> &textures);
-
- // Convenience wrappers.
- void render_to(GLuint depth_rb, GLuint texture0) {
- render_to(depth_rb, {{texture0}});
- }
-
- void render_to(GLuint depth_rb, GLuint texture0, GLuint texture1) {
- render_to(depth_rb, {{texture0, texture1}});
- }
-
- void render_to(GLuint depth_rb, GLuint texture0, GLuint texture1, GLuint texture2) {
- render_to(depth_rb, {{texture0, texture1, texture2}});
- }
-
- void render_to(GLuint depth_rb, GLuint texture0, GLuint texture1, GLuint texture2, GLuint texture3) {
- render_to(depth_rb, {{texture0, texture1, texture2, texture3}});
- }
-
-private:
- // TODO: Delete these on destruction.
- map<pair<GLuint, array<GLuint, num_elements>>, GLuint> fbos;
-};
-
template<size_t num_elements>
void PersistentFBOSetWithDepth<num_elements>::render_to(GLuint depth_rb, const array<GLuint, num_elements> &textures)
{
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, int num_layers);
-
-private:
- PersistentFBOSet<1> fbos;
- GLuint gray_vs_obj;
- GLuint gray_fs_obj;
- GLuint gray_program;
- GLuint gray_vao;
-
- GLuint uniform_tex;
-};
-
GrayscaleConversion::GrayscaleConversion()
{
gray_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
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 tex_view, GLint grad_tex, int level_width, int level_height, int num_layers);
-
-private:
- PersistentFBOSet<1> fbos;
- GLuint sobel_vs_obj;
- GLuint sobel_fs_obj;
- GLuint sobel_program;
-
- GLuint uniform_tex;
-};
-
Sobel::Sobel()
{
sobel_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
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 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);
-
-private:
- PersistentFBOSet<1> fbos;
-
- GLuint motion_vs_obj;
- GLuint motion_fs_obj;
- GLuint motion_search_program;
-
- GLuint uniform_inv_image_size, uniform_inv_prev_level_size, uniform_out_flow_size;
- GLuint uniform_image_tex, uniform_grad_tex, uniform_flow_tex;
-};
-
MotionSearch::MotionSearch()
{
motion_vs_obj = compile_shader(read_file("motion_search.vert"), GL_VERTEX_SHADER);
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 tex_view, GLuint flow_tex, GLuint dense_flow_tex, int level_width, int level_height, int width_patches, int height_patches, int num_layers);
-
-private:
- PersistentFBOSet<1> fbos;
-
- GLuint densify_vs_obj;
- GLuint densify_fs_obj;
- GLuint densify_program;
-
- GLuint uniform_patch_size;
- GLuint uniform_image_tex, uniform_flow_tex;
-};
-
Densify::Densify()
{
densify_vs_obj = compile_shader(read_file("densify.vert"), GL_VERTEX_SHADER);
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 tex_view, GLuint flow_tex, GLuint normalized_flow_tex, GLuint I_tex, GLuint I_t_tex, int level_width, int level_height, int num_layers);
-
-private:
- PersistentFBOSet<3> fbos;
-
- GLuint prewarp_vs_obj;
- GLuint prewarp_fs_obj;
- GLuint prewarp_program;
-
- GLuint uniform_image_tex, uniform_flow_tex;
-};
-
Prewarp::Prewarp()
{
prewarp_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
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, int num_layers);
-
-private:
- PersistentFBOSet<2> fbos;
-
- GLuint derivatives_vs_obj;
- GLuint derivatives_fs_obj;
- GLuint derivatives_program;
-
- GLuint uniform_tex;
-};
-
Derivatives::Derivatives()
{
derivatives_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, num_layers);
}
-// Calculate the diffusivity for each pixels, g(x,y). Smoothness (s) will
-// be calculated in the shaders on-the-fly by sampling in-between two
-// neighboring g(x,y) pixels, plus a border tweak to make sure we get
-// zero smoothness at the border.
-//
-// See variational_refinement.txt for more information.
-class ComputeDiffusivity {
-public:
- ComputeDiffusivity();
- void exec(GLuint flow_tex, GLuint diff_flow_tex, GLuint diffusivity_tex, int level_width, int level_height, bool zero_diff_flow, int num_layers);
-
-private:
- PersistentFBOSet<1> fbos;
-
- GLuint diffusivity_vs_obj;
- GLuint diffusivity_fs_obj;
- GLuint diffusivity_program;
-
- GLuint uniform_flow_tex, uniform_diff_flow_tex;
- GLuint uniform_alpha, uniform_zero_diff_flow;
-};
-
ComputeDiffusivity::ComputeDiffusivity()
{
diffusivity_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
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.
-//
-// The equation set is split in two; one contains only the pixels needed for
-// the red pass, and one only for the black pass (see sor.frag). This reduces
-// the amount of data the SOR shader has to pull in, at the cost of some
-// complexity when the equation texture ends up with half the size and we need
-// to adjust texture coordinates. The contraction is done along the horizontal
-// axis, so that on even rows (0, 2, 4, ...), the “red” texture will contain
-// pixels 0, 2, 4, 6, etc., and on odd rows 1, 3, 5, etc..
-//
-// See variational_refinement.txt for more information about the actual
-// equations in use.
-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 diffusivity_tex, GLuint equation_red_tex, GLuint equation_black_tex, int level_width, int level_height, bool zero_diff_flow, int num_layers);
-
-private:
- PersistentFBOSet<2> fbos;
-
- GLuint equations_vs_obj;
- GLuint equations_fs_obj;
- GLuint equations_program;
-
- 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_diffusivity_tex;
- GLuint uniform_gamma, uniform_delta, uniform_zero_diff_flow;
-};
-
SetupEquations::SetupEquations()
{
equations_vs_obj = compile_shader(read_file("equations.vert"), GL_VERTEX_SHADER);
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_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);
-
-private:
- PersistentFBOSet<1> fbos;
-
- GLuint sor_vs_obj;
- GLuint sor_fs_obj;
- GLuint sor_program;
-
- GLuint uniform_diff_flow_tex;
- GLuint uniform_equation_red_tex, uniform_equation_black_tex;
- GLuint uniform_diffusivity_tex;
- GLuint uniform_phase, uniform_num_nonzero_phases;
-};
-
SOR::SOR()
{
sor_vs_obj = compile_shader(read_file("sor.vert"), GL_VERTEX_SHADER);
}
}
-// 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, int num_layers);
-
-private:
- PersistentFBOSet<1> fbos;
-
- GLuint add_flow_vs_obj;
- GLuint add_flow_fs_obj;
- GLuint add_flow_program;
-
- GLuint uniform_diff_flow_tex;
-};
-
AddBaseFlow::AddBaseFlow()
{
add_flow_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
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, int num_layers);
-
-private:
- PersistentFBOSet<1> fbos;
-
- GLuint resize_flow_vs_obj;
- GLuint resize_flow_fs_obj;
- GLuint resize_flow_program;
-
- GLuint uniform_flow_tex;
- GLuint uniform_scale_factor;
-};
-
ResizeFlow::ResizeFlow()
{
resize_flow_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, num_layers);
}
-class TexturePool {
-public:
- GLuint get_texture(GLenum format, GLuint width, GLuint height, GLuint num_layers = 0);
- void release_texture(GLuint tex_num);
- GLuint get_renderbuffer(GLenum format, GLuint width, GLuint height);
- void release_renderbuffer(GLuint tex_num);
-
-private:
- struct Texture {
- GLuint tex_num;
- GLenum format;
- GLuint width, height, num_layers;
- bool in_use = false;
- bool is_renderbuffer = false;
- };
- vector<Texture> textures;
-};
-
-class DISComputeFlow {
-public:
- DISComputeFlow(int width, int height);
-
- enum FlowDirection {
- FORWARD,
- FORWARD_AND_BACKWARD
- };
- enum ResizeStrategy {
- DO_NOT_RESIZE_FLOW,
- RESIZE_FLOW_TO_FULL_SIZE
- };
-
- // The texture must have two layers (first and second frame).
- // Returns a texture that must be released with release_texture()
- // after use.
- GLuint exec(GLuint tex, FlowDirection flow_direction, ResizeStrategy resize_strategy);
-
- void release_texture(GLuint tex) {
- pool.release_texture(tex);
- }
-
-private:
- int width, height;
- GLuint initial_flow_tex;
- GLuint vertex_vbo, vao;
- TexturePool pool;
-
- // The various passes.
- Sobel sobel;
- MotionSearch motion_search;
- Densify densify;
- Prewarp prewarp;
- Derivatives derivatives;
- ComputeDiffusivity compute_diffusivity;
- SetupEquations setup_equations;
- SOR sor;
- AddBaseFlow add_base_flow;
- ResizeFlow resize_flow;
-};
-
DISComputeFlow::DISComputeFlow(int width, int height)
: width(width), height(height)
{
}
}
-// 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 image_tex, GLuint bidirectional_flow_tex, GLuint flow_tex, GLuint depth_rb, int width, int height, float alpha);
-
-private:
- PersistentFBOSetWithDepth<1> fbos;
-
- GLuint splat_vs_obj;
- GLuint splat_fs_obj;
- GLuint splat_program;
-
- GLuint uniform_splat_size, uniform_alpha;
- GLuint uniform_image_tex, uniform_flow_tex;
- GLuint uniform_inv_flow_size;
-};
-
Splat::Splat()
{
splat_vs_obj = compile_shader(read_file("splat.vert"), GL_VERTEX_SHADER);
glDisable(GL_DEPTH_TEST);
}
-// Doing good and fast hole-filling on a GPU is nontrivial. We choose an option
-// that's fairly simple (given that most holes are really small) and also hopefully
-// cheap should the holes not be so small. Conceptually, we look for the first
-// non-hole to the left of us (ie., shoot a ray until we hit something), then
-// the first non-hole to the right of us, then up and down, and then average them
-// all together. It's going to create “stars” if the holes are big, but OK, that's
-// a tradeoff.
-//
-// Our implementation here is efficient assuming that the hierarchical Z-buffer is
-// on even for shaders that do discard (this typically kills early Z, but hopefully
-// not hierarchical Z); we set up Z so that only holes are written to, which means
-// that as soon as a hole is filled, the rasterizer should just skip it. Most of the
-// fullscreen quads should just be discarded outright, really.
-class HoleFill {
-public:
- HoleFill();
-
- // Output will be in flow_tex, temp_tex[0, 1, 2], representing the filling
- // from the down, left, right and up, respectively. Use HoleBlend to merge
- // them into one.
- void exec(GLuint flow_tex, GLuint depth_rb, GLuint temp_tex[3], int width, int height);
-
-private:
- PersistentFBOSetWithDepth<1> fbos;
-
- GLuint fill_vs_obj;
- GLuint fill_fs_obj;
- GLuint fill_program;
-
- GLuint uniform_tex;
- GLuint uniform_z, uniform_sample_offset;
-};
-
HoleFill::HoleFill()
{
fill_vs_obj = compile_shader(read_file("hole_fill.vert"), GL_VERTEX_SHADER);
glDisable(GL_DEPTH_TEST);
}
-// Blend the four directions from HoleFill into one pixel, so that single-pixel
-// holes become the average of their four neighbors.
-class HoleBlend {
-public:
- HoleBlend();
-
- void exec(GLuint flow_tex, GLuint depth_rb, GLuint temp_tex[3], int width, int height);
-
-private:
- PersistentFBOSetWithDepth<1> fbos;
-
- GLuint blend_vs_obj;
- GLuint blend_fs_obj;
- GLuint blend_program;
-
- GLuint uniform_left_tex, uniform_right_tex, uniform_up_tex, uniform_down_tex;
- GLuint uniform_z, uniform_sample_offset;
-};
-
HoleBlend::HoleBlend()
{
blend_vs_obj = compile_shader(read_file("hole_fill.vert"), GL_VERTEX_SHADER); // Reuse the vertex shader from the fill.
glDisable(GL_DEPTH_TEST);
}
-class Blend {
-public:
- Blend();
- void exec(GLuint image_tex, GLuint flow_tex, GLuint output_tex, int width, int height, float alpha);
-
-private:
- PersistentFBOSet<1> fbos;
- GLuint blend_vs_obj;
- GLuint blend_fs_obj;
- GLuint blend_program;
-
- GLuint uniform_image_tex, uniform_flow_tex;
- GLuint uniform_alpha, uniform_flow_consistency_tolerance;
-};
-
Blend::Blend()
{
blend_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
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. image_tex must be a two-layer RGBA8 texture with mipmaps
- // (unless flow_level == 0).
- GLuint exec(GLuint image_tex, GLuint bidirectional_flow_tex, GLuint width, GLuint height, float alpha);
-
- void release_texture(GLuint tex) {
- pool.release_texture(tex);
- }
-
-private:
- int width, height, flow_level;
- GLuint vertex_vbo, vao;
- TexturePool pool;
-
- Splat splat;
- HoleFill hole_fill;
- HoleBlend hole_blend;
- Blend blend;
-};
-
Interpolate::Interpolate(int width, int height, int flow_level)
: width(width), height(height), flow_level(flow_level) {
// Set up the vertex data that will be shared between all passes.
--- /dev/null
+#ifndef _FLOW_H
+#define _FLOW_H 1
+
+// Code for computing optical flow between two images, and using it to interpolate
+// in-between frames. The main user interface is the Interpolate class.
+
+#include <stdint.h>
+#include <epoxy/gl.h>
+#include <array>
+#include <map>
+#include <vector>
+#include <utility>
+
+class ScopedTimer;
+
+// 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 std::array<GLuint, num_elements> &textures);
+
+ // Convenience wrappers.
+ void render_to(GLuint texture0) {
+ render_to({{texture0}});
+ }
+
+ void render_to(GLuint texture0, GLuint texture1) {
+ render_to({{texture0, texture1}});
+ }
+
+ void render_to(GLuint texture0, GLuint texture1, GLuint texture2) {
+ render_to({{texture0, texture1, texture2}});
+ }
+
+ void render_to(GLuint texture0, GLuint texture1, GLuint texture2, GLuint texture3) {
+ render_to({{texture0, texture1, texture2, texture3}});
+ }
+
+private:
+ // TODO: Delete these on destruction.
+ std::map<std::array<GLuint, num_elements>, GLuint> fbos;
+};
+
+
+// Same, but with a depth texture.
+template<size_t num_elements>
+class PersistentFBOSetWithDepth {
+public:
+ void render_to(GLuint depth_rb, const std::array<GLuint, num_elements> &textures);
+
+ // Convenience wrappers.
+ void render_to(GLuint depth_rb, GLuint texture0) {
+ render_to(depth_rb, {{texture0}});
+ }
+
+ void render_to(GLuint depth_rb, GLuint texture0, GLuint texture1) {
+ render_to(depth_rb, {{texture0, texture1}});
+ }
+
+ void render_to(GLuint depth_rb, GLuint texture0, GLuint texture1, GLuint texture2) {
+ render_to(depth_rb, {{texture0, texture1, texture2}});
+ }
+
+ void render_to(GLuint depth_rb, GLuint texture0, GLuint texture1, GLuint texture2, GLuint texture3) {
+ render_to(depth_rb, {{texture0, texture1, texture2, texture3}});
+ }
+
+private:
+ // TODO: Delete these on destruction.
+ std::map<std::pair<GLuint, std::array<GLuint, num_elements>>, GLuint> fbos;
+};
+
+// Convert RGB to grayscale, using Rec. 709 coefficients.
+class GrayscaleConversion {
+public:
+ GrayscaleConversion();
+ void exec(GLint tex, GLint gray_tex, int width, int height, int num_layers);
+
+private:
+ PersistentFBOSet<1> fbos;
+ GLuint gray_vs_obj;
+ GLuint gray_fs_obj;
+ GLuint gray_program;
+ GLuint gray_vao;
+
+ GLuint uniform_tex;
+};
+
+// 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 tex_view, GLint grad_tex, int level_width, int level_height, int num_layers);
+
+private:
+ PersistentFBOSet<1> fbos;
+ GLuint sobel_vs_obj;
+ GLuint sobel_fs_obj;
+ GLuint sobel_program;
+
+ GLuint uniform_tex;
+};
+
+// Motion search to find the initial flow. See motion_search.frag for documentation.
+class MotionSearch {
+public:
+ MotionSearch();
+ void 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);
+
+private:
+ PersistentFBOSet<1> fbos;
+
+ GLuint motion_vs_obj;
+ GLuint motion_fs_obj;
+ GLuint motion_search_program;
+
+ GLuint uniform_inv_image_size, uniform_inv_prev_level_size, uniform_out_flow_size;
+ GLuint uniform_image_tex, uniform_grad_tex, uniform_flow_tex;
+};
+
+// 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 tex_view, GLuint flow_tex, GLuint dense_flow_tex, int level_width, int level_height, int width_patches, int height_patches, int num_layers);
+
+private:
+ PersistentFBOSet<1> fbos;
+
+ GLuint densify_vs_obj;
+ GLuint densify_fs_obj;
+ GLuint densify_program;
+
+ GLuint uniform_patch_size;
+ GLuint uniform_image_tex, uniform_flow_tex;
+};
+
+// 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 tex_view, GLuint flow_tex, GLuint normalized_flow_tex, GLuint I_tex, GLuint I_t_tex, int level_width, int level_height, int num_layers);
+
+private:
+ PersistentFBOSet<3> fbos;
+
+ GLuint prewarp_vs_obj;
+ GLuint prewarp_fs_obj;
+ GLuint prewarp_program;
+
+ GLuint uniform_image_tex, uniform_flow_tex;
+};
+
+// 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, int num_layers);
+
+private:
+ PersistentFBOSet<2> fbos;
+
+ GLuint derivatives_vs_obj;
+ GLuint derivatives_fs_obj;
+ GLuint derivatives_program;
+
+ GLuint uniform_tex;
+};
+
+// Calculate the diffusivity for each pixels, g(x,y). Smoothness (s) will
+// be calculated in the shaders on-the-fly by sampling in-between two
+// neighboring g(x,y) pixels, plus a border tweak to make sure we get
+// zero smoothness at the border.
+//
+// See variational_refinement.txt for more information.
+class ComputeDiffusivity {
+public:
+ ComputeDiffusivity();
+ void exec(GLuint flow_tex, GLuint diff_flow_tex, GLuint diffusivity_tex, int level_width, int level_height, bool zero_diff_flow, int num_layers);
+
+private:
+ PersistentFBOSet<1> fbos;
+
+ GLuint diffusivity_vs_obj;
+ GLuint diffusivity_fs_obj;
+ GLuint diffusivity_program;
+
+ GLuint uniform_flow_tex, uniform_diff_flow_tex;
+ GLuint uniform_alpha, uniform_zero_diff_flow;
+};
+
+// 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.
+//
+// The equation set is split in two; one contains only the pixels needed for
+// the red pass, and one only for the black pass (see sor.frag). This reduces
+// the amount of data the SOR shader has to pull in, at the cost of some
+// complexity when the equation texture ends up with half the size and we need
+// to adjust texture coordinates. The contraction is done along the horizontal
+// axis, so that on even rows (0, 2, 4, ...), the “red” texture will contain
+// pixels 0, 2, 4, 6, etc., and on odd rows 1, 3, 5, etc..
+//
+// See variational_refinement.txt for more information about the actual
+// equations in use.
+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 diffusivity_tex, GLuint equation_red_tex, GLuint equation_black_tex, int level_width, int level_height, bool zero_diff_flow, int num_layers);
+
+private:
+ PersistentFBOSet<2> fbos;
+
+ GLuint equations_vs_obj;
+ GLuint equations_fs_obj;
+ GLuint equations_program;
+
+ 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_diffusivity_tex;
+ GLuint uniform_gamma, uniform_delta, uniform_zero_diff_flow;
+};
+
+// 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_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);
+
+private:
+ PersistentFBOSet<1> fbos;
+
+ GLuint sor_vs_obj;
+ GLuint sor_fs_obj;
+ GLuint sor_program;
+
+ GLuint uniform_diff_flow_tex;
+ GLuint uniform_equation_red_tex, uniform_equation_black_tex;
+ GLuint uniform_diffusivity_tex;
+ GLuint uniform_phase, uniform_num_nonzero_phases;
+};
+
+// 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, int num_layers);
+
+private:
+ PersistentFBOSet<1> fbos;
+
+ GLuint add_flow_vs_obj;
+ GLuint add_flow_fs_obj;
+ GLuint add_flow_program;
+
+ GLuint uniform_diff_flow_tex;
+};
+
+// 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, int num_layers);
+
+private:
+ PersistentFBOSet<1> fbos;
+
+ GLuint resize_flow_vs_obj;
+ GLuint resize_flow_fs_obj;
+ GLuint resize_flow_program;
+
+ GLuint uniform_flow_tex;
+ GLuint uniform_scale_factor;
+};
+
+class TexturePool {
+public:
+ GLuint get_texture(GLenum format, GLuint width, GLuint height, GLuint num_layers = 0);
+ void release_texture(GLuint tex_num);
+ GLuint get_renderbuffer(GLenum format, GLuint width, GLuint height);
+ void release_renderbuffer(GLuint tex_num);
+
+private:
+ struct Texture {
+ GLuint tex_num;
+ GLenum format;
+ GLuint width, height, num_layers;
+ bool in_use = false;
+ bool is_renderbuffer = false;
+ };
+ std::vector<Texture> textures;
+};
+
+class DISComputeFlow {
+public:
+ DISComputeFlow(int width, int height);
+
+ enum FlowDirection {
+ FORWARD,
+ FORWARD_AND_BACKWARD
+ };
+ enum ResizeStrategy {
+ DO_NOT_RESIZE_FLOW,
+ RESIZE_FLOW_TO_FULL_SIZE
+ };
+
+ // The texture must have two layers (first and second frame).
+ // Returns a texture that must be released with release_texture()
+ // after use.
+ GLuint exec(GLuint tex, FlowDirection flow_direction, ResizeStrategy resize_strategy);
+
+ void release_texture(GLuint tex) {
+ pool.release_texture(tex);
+ }
+
+private:
+ int width, height;
+ GLuint initial_flow_tex;
+ GLuint vertex_vbo, vao;
+ TexturePool pool;
+
+ // The various passes.
+ Sobel sobel;
+ MotionSearch motion_search;
+ Densify densify;
+ Prewarp prewarp;
+ Derivatives derivatives;
+ ComputeDiffusivity compute_diffusivity;
+ SetupEquations setup_equations;
+ SOR sor;
+ AddBaseFlow add_base_flow;
+ ResizeFlow resize_flow;
+};
+
+// 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 image_tex, GLuint bidirectional_flow_tex, GLuint flow_tex, GLuint depth_rb, int width, int height, float alpha);
+
+private:
+ PersistentFBOSetWithDepth<1> fbos;
+
+ GLuint splat_vs_obj;
+ GLuint splat_fs_obj;
+ GLuint splat_program;
+
+ GLuint uniform_splat_size, uniform_alpha;
+ GLuint uniform_image_tex, uniform_flow_tex;
+ GLuint uniform_inv_flow_size;
+};
+
+// Doing good and fast hole-filling on a GPU is nontrivial. We choose an option
+// that's fairly simple (given that most holes are really small) and also hopefully
+// cheap should the holes not be so small. Conceptually, we look for the first
+// non-hole to the left of us (ie., shoot a ray until we hit something), then
+// the first non-hole to the right of us, then up and down, and then average them
+// all together. It's going to create “stars” if the holes are big, but OK, that's
+// a tradeoff.
+//
+// Our implementation here is efficient assuming that the hierarchical Z-buffer is
+// on even for shaders that do discard (this typically kills early Z, but hopefully
+// not hierarchical Z); we set up Z so that only holes are written to, which means
+// that as soon as a hole is filled, the rasterizer should just skip it. Most of the
+// fullscreen quads should just be discarded outright, really.
+class HoleFill {
+public:
+ HoleFill();
+
+ // Output will be in flow_tex, temp_tex[0, 1, 2], representing the filling
+ // from the down, left, right and up, respectively. Use HoleBlend to merge
+ // them into one.
+ void exec(GLuint flow_tex, GLuint depth_rb, GLuint temp_tex[3], int width, int height);
+
+private:
+ PersistentFBOSetWithDepth<1> fbos;
+
+ GLuint fill_vs_obj;
+ GLuint fill_fs_obj;
+ GLuint fill_program;
+
+ GLuint uniform_tex;
+ GLuint uniform_z, uniform_sample_offset;
+};
+
+// Blend the four directions from HoleFill into one pixel, so that single-pixel
+// holes become the average of their four neighbors.
+class HoleBlend {
+public:
+ HoleBlend();
+
+ void exec(GLuint flow_tex, GLuint depth_rb, GLuint temp_tex[3], int width, int height);
+
+private:
+ PersistentFBOSetWithDepth<1> fbos;
+
+ GLuint blend_vs_obj;
+ GLuint blend_fs_obj;
+ GLuint blend_program;
+
+ GLuint uniform_left_tex, uniform_right_tex, uniform_up_tex, uniform_down_tex;
+ GLuint uniform_z, uniform_sample_offset;
+};
+
+class Blend {
+public:
+ Blend();
+ void exec(GLuint image_tex, GLuint flow_tex, GLuint output_tex, int width, int height, float alpha);
+
+private:
+ PersistentFBOSet<1> fbos;
+ GLuint blend_vs_obj;
+ GLuint blend_fs_obj;
+ GLuint blend_program;
+
+ GLuint uniform_image_tex, uniform_flow_tex;
+ GLuint uniform_alpha, uniform_flow_consistency_tolerance;
+};
+
+class Interpolate {
+public:
+ Interpolate(int width, int height, int flow_level);
+
+ // Returns a texture that must be released with release_texture()
+ // after use. image_tex must be a two-layer RGBA8 texture with mipmaps
+ // (unless flow_level == 0).
+ GLuint exec(GLuint image_tex, GLuint bidirectional_flow_tex, GLuint width, GLuint height, float alpha);
+
+ void release_texture(GLuint tex) {
+ pool.release_texture(tex);
+ }
+
+private:
+ int width, height, flow_level;
+ GLuint vertex_vbo, vao;
+ TexturePool pool;
+
+ Splat splat;
+ HoleFill hole_fill;
+ HoleBlend hole_blend;
+ Blend blend;
+};
+
+#endif // !defined(_FLOW_H)
projects / nageru / commitdiff