]> git.sesse.net Git - nageru/blobdiff - flow.cpp
av_register_all() is deprecated, so do not call it anymore (no replacement needed).
[nageru] / flow.cpp
index 1e4873362c1586e0f3a1095e74b38ec1b4a6bb2a..b673b9d91cbde9dd14a98dfeb432e4709e3c599f 100644 (file)
--- a/flow.cpp
+++ b/flow.cpp
@@ -48,6 +48,8 @@ float vr_alpha = 1.0f, vr_delta = 0.25f, vr_gamma = 0.25f;
 
 bool enable_timing = true;
 bool detailed_timing = false;
+bool enable_warmup = false;
+bool in_warmup = false;
 bool enable_variational_refinement = true;  // Just for debugging.
 bool enable_interpolation = false;
 
@@ -289,23 +291,23 @@ void PersistentFBOSet<num_elements>::render_to(const array<GLuint, num_elements>
 template<size_t num_elements>
 class PersistentFBOSetWithDepth {
 public:
-       void render_to(GLuint depth_tex, const array<GLuint, num_elements> &textures);
+       void render_to(GLuint depth_rb, const array<GLuint, num_elements> &textures);
 
        // Convenience wrappers.
-       void render_to(GLuint depth_tex, GLuint texture0) {
-               render_to(depth_tex, {{texture0}});
+       void render_to(GLuint depth_rb, GLuint texture0) {
+               render_to(depth_rb, {{texture0}});
        }
 
-       void render_to(GLuint depth_tex, GLuint texture0, GLuint texture1) {
-               render_to(depth_tex, {{texture0, texture1}});
+       void render_to(GLuint depth_rb, GLuint texture0, GLuint texture1) {
+               render_to(depth_rb, {{texture0, texture1}});
        }
 
-       void render_to(GLuint depth_tex, GLuint texture0, GLuint texture1, GLuint texture2) {
-               render_to(depth_tex, {{texture0, texture1, texture2}});
+       void render_to(GLuint depth_rb, GLuint texture0, GLuint texture1, GLuint texture2) {
+               render_to(depth_rb, {{texture0, texture1, texture2}});
        }
 
-       void render_to(GLuint depth_tex, GLuint texture0, GLuint texture1, GLuint texture2, GLuint texture3) {
-               render_to(depth_tex, {{texture0, texture1, texture2, texture3}});
+       void render_to(GLuint depth_rb, GLuint texture0, GLuint texture1, GLuint texture2, GLuint texture3) {
+               render_to(depth_rb, {{texture0, texture1, texture2, texture3}});
        }
 
 private:
@@ -314,9 +316,9 @@ private:
 };
 
 template<size_t num_elements>
-void PersistentFBOSetWithDepth<num_elements>::render_to(GLuint depth_tex, const array<GLuint, num_elements> &textures)
+void PersistentFBOSetWithDepth<num_elements>::render_to(GLuint depth_rb, const array<GLuint, num_elements> &textures)
 {
-       auto key = make_pair(depth_tex, textures);
+       auto key = make_pair(depth_rb, textures);
 
        auto it = fbos.find(key);
        if (it != fbos.end()) {
@@ -327,7 +329,7 @@ void PersistentFBOSetWithDepth<num_elements>::render_to(GLuint depth_tex, const
        GLuint fbo;
        glCreateFramebuffers(1, &fbo);
        GLenum bufs[num_elements];
-       glNamedFramebufferTexture(fbo, GL_DEPTH_ATTACHMENT, depth_tex, 0);
+       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;
@@ -342,7 +344,7 @@ void PersistentFBOSetWithDepth<num_elements>::render_to(GLuint depth_tex, const
 class GrayscaleConversion {
 public:
        GrayscaleConversion();
-       void exec(GLint tex, GLint gray_tex, int width, int height);
+       void exec(GLint tex, GLint gray_tex, int width, int height, int num_layers);
 
 private:
        PersistentFBOSet<1> fbos;
@@ -371,7 +373,7 @@ 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);
@@ -380,7 +382,7 @@ void GrayscaleConversion::exec(GLint tex, GLint gray_tex, int width, int height)
        fbos.render_to(gray_tex);
        glBindVertexArray(gray_vao);
        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.
@@ -394,7 +396,7 @@ void GrayscaleConversion::exec(GLint tex, GLint gray_tex, int width, int height)
 class Sobel {
 public:
        Sobel();
-       void exec(GLint tex0_view, GLint grad0_tex, int level_width, int level_height);
+       void exec(GLint tex_view, GLint grad_tex, int level_width, int level_height, int num_layers);
 
 private:
        PersistentFBOSet<1> fbos;
@@ -414,22 +416,22 @@ Sobel::Sobel()
        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);
+       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);
+       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;
@@ -438,8 +440,8 @@ private:
        GLuint motion_fs_obj;
        GLuint motion_search_program;
 
-       GLuint uniform_inv_image_size, uniform_inv_prev_level_size;
-       GLuint uniform_image1_tex, uniform_grad0_tex, uniform_flow_tex;
+       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()
@@ -450,25 +452,27 @@ MotionSearch::MotionSearch()
 
        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_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");
 }
 
-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_image1_tex, 1, tex1_view, linear_sampler);
-       bind_sampler(motion_search_program, uniform_grad0_tex, 2, grad0_tex, nearest_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);
 
        glViewport(0, 0, width_patches, height_patches);
        fbos.render_to(flow_out_tex);
-       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
@@ -482,7 +486,7 @@ void MotionSearch::exec(GLuint tex0_view, GLuint tex1_view, GLuint grad0_tex, GL
 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);
+       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;
@@ -492,7 +496,7 @@ private:
        GLuint densify_program;
 
        GLuint uniform_patch_size;
-       GLuint uniform_image0_tex, uniform_image1_tex, uniform_flow_tex;
+       GLuint uniform_image_tex, uniform_flow_tex;
 };
 
 Densify::Densify()
@@ -502,18 +506,16 @@ Densify::Densify()
        densify_program = link_program(densify_vs_obj, densify_fs_obj);
 
        uniform_patch_size = glGetUniformLocation(densify_program, "patch_size");
-       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,
@@ -525,7 +527,7 @@ void Densify::exec(GLuint tex0_view, GLuint tex1_view, GLuint flow_tex, GLuint d
        fbos.render_to(dense_flow_tex);
        glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
        glClear(GL_COLOR_BUFFER_BIT);
-       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, width_patches * height_patches);
+       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
@@ -539,7 +541,7 @@ void Densify::exec(GLuint tex0_view, GLuint tex1_view, GLuint flow_tex, GLuint d
 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);
+       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;
@@ -548,7 +550,7 @@ private:
        GLuint prewarp_fs_obj;
        GLuint prewarp_program;
 
-       GLuint uniform_image0_tex, uniform_image1_tex, uniform_flow_tex;
+       GLuint uniform_image_tex, uniform_flow_tex;
 };
 
 Prewarp::Prewarp()
@@ -557,23 +559,21 @@ Prewarp::Prewarp()
        prewarp_fs_obj = compile_shader(read_file("prewarp.frag"), GL_FRAGMENT_SHADER);
        prewarp_program = link_program(prewarp_vs_obj, prewarp_fs_obj);
 
-       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);
        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
@@ -587,7 +587,7 @@ void Prewarp::exec(GLuint tex0_view, GLuint tex1_view, GLuint flow_tex, GLuint I
 class Derivatives {
 public:
        Derivatives();
-       void exec(GLuint input_tex, GLuint I_x_y_tex, GLuint beta_0_tex, int level_width, int level_height);
+       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;
@@ -608,7 +608,7 @@ Derivatives::Derivatives()
        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);
 
@@ -617,7 +617,7 @@ 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);
        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 diffusivity for each pixels, g(x,y). Smoothness (s) will
@@ -629,7 +629,7 @@ void Derivatives::exec(GLuint input_tex, GLuint I_x_y_tex, GLuint beta_0_tex, in
 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);
+       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;
@@ -654,7 +654,7 @@ ComputeDiffusivity::ComputeDiffusivity()
        uniform_zero_diff_flow = glGetUniformLocation(diffusivity_program, "zero_diff_flow");
 }
 
-void ComputeDiffusivity::exec(GLuint flow_tex, GLuint diff_flow_tex, GLuint diffusivity_tex, int level_width, int level_height, bool zero_diff_flow)
+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(diffusivity_program);
 
@@ -667,7 +667,7 @@ void ComputeDiffusivity::exec(GLuint flow_tex, GLuint diff_flow_tex, GLuint diff
 
        glDisable(GL_BLEND);
        fbos.render_to(diffusivity_tex);
-       glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, num_layers);
 }
 
 // Set up the equations set (two equations in two unknowns, per pixel).
@@ -692,7 +692,7 @@ void ComputeDiffusivity::exec(GLuint flow_tex, GLuint diff_flow_tex, GLuint diff
 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);
+       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;
@@ -725,7 +725,7 @@ SetupEquations::SetupEquations()
        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 diffusivity_tex, GLuint equation_red_tex, GLuint equation_black_tex, int level_width, int level_height, bool 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 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);
 
@@ -741,8 +741,8 @@ void SetupEquations::exec(GLuint I_x_y_tex, GLuint I_t_tex, GLuint diff_flow_tex
 
        glViewport(0, 0, (level_width + 1) / 2, level_height);
        glDisable(GL_BLEND);
-       fbos.render_to({equation_red_tex, equation_black_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
@@ -752,7 +752,7 @@ void SetupEquations::exec(GLuint I_x_y_tex, GLuint I_t_tex, GLuint diff_flow_tex
 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, ScopedTimer *sor_timer);
+       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;
@@ -764,7 +764,7 @@ private:
        GLuint uniform_diff_flow_tex;
        GLuint uniform_equation_red_tex, uniform_equation_black_tex;
        GLuint uniform_diffusivity_tex;
-       GLuint uniform_phase, uniform_zero_diff_flow;
+       GLuint uniform_phase, uniform_num_nonzero_phases;
 };
 
 SOR::SOR()
@@ -778,10 +778,10 @@ SOR::SOR()
        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_zero_diff_flow = glGetUniformLocation(sor_program, "zero_diff_flow");
+       uniform_num_nonzero_phases = glGetUniformLocation(sor_program, "num_nonzero_phases");
 }
 
-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, ScopedTimer *sor_timer)
+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);
 
@@ -790,7 +790,9 @@ void SOR::exec(GLuint diff_flow_tex, GLuint equation_red_tex, GLuint equation_bl
        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);
 
-       glProgramUniform1i(sor_program, uniform_zero_diff_flow, zero_diff_flow);
+       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
@@ -803,18 +805,23 @@ void SOR::exec(GLuint diff_flow_tex, GLuint equation_red_tex, GLuint equation_bl
        for (int i = 0; i < num_iterations; ++i) {
                {
                        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);
-                       glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+                       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, num_layers);
                        glTextureBarrier();
                }
                {
                        ScopedTimer timer("Black pass", sor_timer);
                        if (zero_diff_flow && i == 0) {
-                               // Not zero anymore.
-                               glProgramUniform1i(sor_program, uniform_zero_diff_flow, 0);
+                               glProgramUniform1i(sor_program, uniform_num_nonzero_phases, 1);
                        }
                        glProgramUniform1i(sor_program, uniform_phase, 1);
-                       glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+                       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();
                        }
@@ -827,7 +834,7 @@ void SOR::exec(GLuint diff_flow_tex, GLuint equation_red_tex, GLuint equation_bl
 class AddBaseFlow {
 public:
        AddBaseFlow();
-       void exec(GLuint base_flow_tex, GLuint diff_flow_tex, int level_width, int level_height);
+       void exec(GLuint base_flow_tex, GLuint diff_flow_tex, int level_width, int level_height, int num_layers);
 
 private:
        PersistentFBOSet<1> fbos;
@@ -848,7 +855,7 @@ AddBaseFlow::AddBaseFlow()
        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);
 
@@ -859,14 +866,14 @@ void AddBaseFlow::exec(GLuint base_flow_tex, GLuint diff_flow_tex, int level_wid
        glBlendFunc(GL_ONE, GL_ONE);
        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);
+       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;
@@ -889,7 +896,7 @@ ResizeFlow::ResizeFlow()
        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);
 
@@ -901,20 +908,23 @@ void ResizeFlow::exec(GLuint flow_tex, GLuint out_tex, int input_width, int inpu
        glDisable(GL_BLEND);
        fbos.render_to(out_tex);
 
-       glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+       glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, num_layers);
 }
 
 class TexturePool {
 public:
-       GLuint get_texture(GLenum format, GLuint width, GLuint height);
+       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;
+               GLuint width, height, num_layers;
                bool in_use = false;
+               bool is_renderbuffer = false;
        };
        vector<Texture> textures;
 };
@@ -923,14 +933,19 @@ 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 tex0, GLuint tex1, ResizeStrategy resize_strategy);
+       GLuint exec(GLuint tex, FlowDirection flow_direction, ResizeStrategy resize_strategy);
 
        void release_texture(GLuint tex) {
                pool.release_texture(tex);
@@ -984,8 +999,8 @@ DISComputeFlow::DISComputeFlow(int width, int height)
        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.
@@ -1007,8 +1022,9 @@ DISComputeFlow::DISComputeFlow(int width, int height)
        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;
 
@@ -1016,7 +1032,7 @@ GLuint DISComputeFlow::exec(GLuint tex0, GLuint tex1, ResizeStrategy resize_stra
 
        glBindVertexArray(vao);
 
-       ScopedTimer total_timer("Total", &timers);
+       ScopedTimer total_timer("Compute flow", &timers);
        for (int level = coarsest_level; level >= int(finest_level); --level) {
                char timer_name[256];
                snprintf(timer_name, sizeof(timer_name), "Level %d (%d x %d)", level, width >> level, height >> level);
@@ -1036,44 +1052,41 @@ 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_R32UI, 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 (cleared in Densify).
-               GLuint dense_flow_tex = pool.get_texture(GL_RGB16F, level_width, level_height);
+               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);
 
@@ -1087,61 +1100,59 @@ 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);
+               glDeleteTextures(1, &tex_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);
+               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("First derivatives", &varref_timer);
-                       derivatives.exec(I_tex, I_x_y_tex, beta_0_tex, level_width, level_height);
+                       derivatives.exec(I_tex, I_x_y_tex, beta_0_tex, level_width, level_height, num_layers);
                }
                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 du_dv_tex = pool.get_texture(GL_RG16F, level_width, level_height);
+               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);
+               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);
-               GLuint equation_black_tex = pool.get_texture(GL_RGBA32UI, (level_width + 1) / 2, level_height);
+               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, du_dv_tex, diffusivity_tex, level_width, level_height, outer_idx == 0);
+                               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, du_dv_tex, base_flow_tex, beta_0_tex, diffusivity_tex, equation_red_tex, equation_black_tex, level_width, level_height, outer_idx == 0);
+                               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 (or quasi-SOR, since we're not really Jacobi) iterations.
-                       // Note that these are to/from the same texture.
+                       // Run a few SOR iterations. Note that these are to/from the same texture.
                        {
                                ScopedTimer timer("SOR", &varref_timer);
-                               sor.exec(du_dv_tex, equation_red_tex, equation_black_tex, diffusivity_tex, level_width, level_height, 5, outer_idx == 0, &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);
                        }
                }
 
@@ -1160,9 +1171,9 @@ GLuint DISComputeFlow::exec(GLuint tex0, GLuint tex1, ResizeStrategy resize_stra
                // 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);
+                       add_base_flow.exec(base_flow_tex, diff_flow_tex, level_width, level_height, num_layers);
                }
-               pool.release_texture(du_dv_tex);
+               pool.release_texture(diff_flow_tex);
 
                if (prev_level_flow_tex != initial_flow_tex) {
                        pool.release_texture(prev_level_flow_tex);
@@ -1173,14 +1184,16 @@ 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) {
                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;
        }
@@ -1193,7 +1206,7 @@ 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);
+       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;
@@ -1202,8 +1215,8 @@ private:
        GLuint splat_fs_obj;
        GLuint splat_program;
 
-       GLuint uniform_invert_flow, uniform_splat_size, uniform_alpha;
-       GLuint uniform_image0_tex, uniform_image1_tex, uniform_flow_tex;
+       GLuint uniform_splat_size, uniform_alpha;
+       GLuint uniform_image_tex, uniform_flow_tex;
        GLuint uniform_inv_flow_size;
 };
 
@@ -1213,21 +1226,19 @@ Splat::Splat()
        splat_fs_obj = compile_shader(read_file("splat.frag"), GL_FRAGMENT_SHADER);
        splat_program = link_program(splat_vs_obj, splat_fs_obj);
 
-       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_image_tex = glGetUniformLocation(splat_program, "image_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 image_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_image_tex, 0, image_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, or even 4.0.
@@ -1243,7 +1254,7 @@ void Splat::exec(GLuint tex0, GLuint tex1, GLuint forward_flow_tex, GLuint backw
        glEnable(GL_DEPTH_TEST);
        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.)
 
-       fbos.render_to(depth_tex, flow_tex);
+       fbos.render_to(depth_rb, flow_tex);
 
        // Evidently NVIDIA doesn't use fast clears for glClearTexImage, so clear now that
        // we've got it bound.
@@ -1251,15 +1262,7 @@ void Splat::exec(GLuint tex0, GLuint tex1, GLuint forward_flow_tex, GLuint backw
        glClearDepth(1.0f);  // Effectively infinity.
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 
-       // 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);
-
-       // 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);
 }
@@ -1284,7 +1287,7 @@ public:
        // 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_tex, GLuint temp_tex[3], int width, int height);
+       void exec(GLuint flow_tex, GLuint depth_rb, GLuint temp_tex[3], int width, int height);
 
 private:
        PersistentFBOSetWithDepth<1> fbos;
@@ -1308,7 +1311,7 @@ HoleFill::HoleFill()
        uniform_sample_offset = glGetUniformLocation(fill_program, "sample_offset");
 }
 
-void HoleFill::exec(GLuint flow_tex, GLuint depth_tex, GLuint temp_tex[3], int width, int height)
+void HoleFill::exec(GLuint flow_tex, GLuint depth_rb, GLuint temp_tex[3], int width, int height)
 {
        glUseProgram(fill_program);
 
@@ -1321,7 +1324,7 @@ void HoleFill::exec(GLuint flow_tex, GLuint depth_tex, GLuint temp_tex[3], int w
        glEnable(GL_DEPTH_TEST);
        glDepthFunc(GL_LESS);  // Only update the values > 0.999f (ie., only invalid pixels).
 
-       fbos.render_to(depth_tex, flow_tex);  // NOTE: Reading and writing to the same texture.
+       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) {
@@ -1367,7 +1370,7 @@ class HoleBlend {
 public:
        HoleBlend();
 
-       void exec(GLuint flow_tex, GLuint depth_tex, GLuint temp_tex[3], int width, int height);
+       void exec(GLuint flow_tex, GLuint depth_rb, GLuint temp_tex[3], int width, int height);
 
 private:
        PersistentFBOSetWithDepth<1> fbos;
@@ -1394,7 +1397,7 @@ HoleBlend::HoleBlend()
        uniform_sample_offset = glGetUniformLocation(blend_program, "sample_offset");
 }
 
-void HoleBlend::exec(GLuint flow_tex, GLuint depth_tex, GLuint temp_tex[3], int width, int height)
+void HoleBlend::exec(GLuint flow_tex, GLuint depth_rb, GLuint temp_tex[3], int width, int height)
 {
        glUseProgram(blend_program);
 
@@ -1411,7 +1414,7 @@ void HoleBlend::exec(GLuint flow_tex, GLuint depth_tex, GLuint temp_tex[3], int
        glEnable(GL_DEPTH_TEST);
        glDepthFunc(GL_LEQUAL);  // Skip over all of the pixels that were never holes to begin with.
 
-       fbos.render_to(depth_tex, flow_tex);  // NOTE: Reading and writing to the same texture.
+       fbos.render_to(depth_rb, flow_tex);  // NOTE: Reading and writing to the same texture.
 
        glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 
@@ -1421,7 +1424,7 @@ void HoleBlend::exec(GLuint flow_tex, GLuint depth_tex, GLuint temp_tex[3], int
 class Blend {
 public:
        Blend();
-       void exec(GLuint tex0, GLuint tex1, GLuint flow_tex, GLuint output_tex, int width, int height, float alpha);
+       void exec(GLuint image_tex, GLuint flow_tex, GLuint output_tex, int width, int height, float alpha);
 
 private:
        PersistentFBOSet<1> fbos;
@@ -1429,7 +1432,7 @@ private:
        GLuint blend_fs_obj;
        GLuint blend_program;
 
-       GLuint uniform_image0_tex, uniform_image1_tex, uniform_flow_tex;
+       GLuint uniform_image_tex, uniform_flow_tex;
        GLuint uniform_alpha, uniform_flow_consistency_tolerance;
 };
 
@@ -1439,19 +1442,17 @@ Blend::Blend()
        blend_fs_obj = compile_shader(read_file("blend.frag"), GL_FRAGMENT_SHADER);
        blend_program = link_program(blend_vs_obj, blend_fs_obj);
 
-       uniform_image0_tex = glGetUniformLocation(blend_program, "image0_tex");
-       uniform_image1_tex = glGetUniformLocation(blend_program, "image1_tex");
+       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, 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);
 
        glViewport(0, 0, level_width, level_height);
@@ -1465,9 +1466,9 @@ 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
+       // after use. image_tex must be a two-layer RGBA8 texture 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);
+       GLuint exec(GLuint image_tex, GLuint bidirectional_flow_tex, GLuint width, GLuint height, float alpha);
 
        void release_texture(GLuint tex) {
                pool.release_texture(tex);
@@ -1505,33 +1506,30 @@ Interpolate::Interpolate(int width, int height, int flow_level)
        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)
+GLuint Interpolate::exec(GLuint image_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);
 
        // 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, image_tex, GL_RGBA8, 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.
+       GLuint depth_rb = pool.get_renderbuffer(GL_DEPTH_COMPONENT16, flow_width, flow_height);  // Used for ranking flows.
 
        {
                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);
        }
-       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);
@@ -1540,31 +1538,61 @@ GLuint Interpolate::exec(GLuint tex0, GLuint tex1, GLuint forward_flow_tex, GLui
 
        {
                ScopedTimer timer("Fill holes", &total_timer);
-               hole_fill.exec(flow_tex, depth_tex, temp_tex, flow_width, flow_height);
-               hole_blend.exec(flow_tex, depth_tex, temp_tex, flow_width, flow_height);
+               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);
        }
 
        pool.release_texture(temp_tex[0]);
        pool.release_texture(temp_tex[1]);
        pool.release_texture(temp_tex[2]);
-       pool.release_texture(depth_tex);
+       pool.release_renderbuffer(depth_rb);
 
        GLuint output_tex = pool.get_texture(GL_RGBA8, width, height);
        {
                ScopedTimer timer("Blend", &total_timer);
-               blend.exec(tex0, tex1, flow_tex, output_tex, width, height, alpha);
+               blend.exec(image_tex, flow_tex, output_tex, width, height, alpha);
        }
        pool.release_texture(flow_tex);
        total_timer.end();
-       timers.print();
+       if (!in_warmup) {
+               timers.print();
+       }
 
        return output_tex;
 }
 
-GLuint TexturePool::get_texture(GLenum format, GLuint width, GLuint height)
+GLuint TexturePool::get_texture(GLenum format, GLuint width, GLuint height, GLuint num_layers)
 {
        for (Texture &tex : textures) {
-               if (!tex.in_use && tex.format == format &&
+               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;
+               }
+       }
+
+       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);
+       }
+       tex.format = format;
+       tex.width = width;
+       tex.height = height;
+       tex.num_layers = num_layers;
+       tex.in_use = true;
+       tex.is_renderbuffer = false;
+       textures.push_back(tex);
+       return tex.tex_num;
+}
+
+GLuint TexturePool::get_renderbuffer(GLenum format, GLuint width, GLuint height)
+{
+       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;
@@ -1572,12 +1600,14 @@ GLuint TexturePool::get_texture(GLenum format, GLuint width, GLuint height)
        }
 
        Texture tex;
-       glCreateTextures(GL_TEXTURE_2D, 1, &tex.tex_num);
-       glTextureStorage2D(tex.tex_num, 1, format, width, height);
+       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;
        textures.push_back(tex);
        return tex.tex_num;
 }
@@ -1585,7 +1615,7 @@ GLuint TexturePool::get_texture(GLenum format, GLuint width, GLuint height)
 void TexturePool::release_texture(GLuint tex_num)
 {
        for (Texture &tex : textures) {
-               if (tex.tex_num == tex_num) {
+               if (!tex.is_renderbuffer && tex.tex_num == tex_num) {
                        assert(tex.in_use);
                        tex.in_use = false;
                        return;
@@ -1594,6 +1624,18 @@ void TexturePool::release_texture(GLuint tex_num)
        assert(false);
 }
 
+void TexturePool::release_renderbuffer(GLuint tex_num)
+{
+       for (Texture &tex : textures) {
+               if (tex.is_renderbuffer && tex.tex_num == tex_num) {
+                       assert(tex.in_use);
+                       tex.in_use = false;
+                       return;
+               }
+       }
+       //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)
 {
@@ -1736,32 +1778,47 @@ void compute_flow_only(int argc, char **argv, int optind)
                exit(1);
        }
 
+       // Move them into an array texture, since that's how the rest of the code
+       // would like them.
+       GLuint image_tex;
+       glCreateTextures(GL_TEXTURE_2D_ARRAY, 1, &image_tex);
+       glTextureStorage3D(image_tex, 1, GL_RGBA8, width1, height1, 2);
+       glCopyImageSubData(tex0, GL_TEXTURE_2D, 0, 0, 0, 0, image_tex, GL_TEXTURE_2D_ARRAY, 0, 0, 0, 0, width1, height1, 1);
+       glCopyImageSubData(tex1, GL_TEXTURE_2D, 0, 0, 0, 0, image_tex, GL_TEXTURE_2D_ARRAY, 0, 0, 0, 1, width1, height1, 1);
+       glDeleteTextures(1, &tex0);
+       glDeleteTextures(1, &tex1);
+
        // 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);
+               glNamedBufferData(pbos[i], width1 * height1 * 2 * 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);
+       GLuint tex_gray;
+       glCreateTextures(GL_TEXTURE_2D_ARRAY, 1, &tex_gray);
+       glTextureStorage3D(tex_gray, levels, GL_R8, width1, height1, 2);
 
-       gray.exec(tex1, tex1_gray, width1, height1);
-       glDeleteTextures(1, &tex1);
-       glGenerateTextureMipmap(tex1_gray);
+       GrayscaleConversion gray;
+       gray.exec(image_tex, tex_gray, width1, height1, /*num_layers=*/2);
+       glGenerateTextureMipmap(tex_gray);
 
        DISComputeFlow compute_flow(width1, height1);
-       GLuint final_tex = compute_flow.exec(tex0_gray, tex1_gray, DISComputeFlow::RESIZE_FLOW_TO_FULL_SIZE);
+
+       if (enable_warmup) {
+               in_warmup = true;
+               for (int i = 0; i < 10; ++i) {
+                       GLuint final_tex = compute_flow.exec(tex_gray, DISComputeFlow::FORWARD, DISComputeFlow::RESIZE_FLOW_TO_FULL_SIZE);
+                       compute_flow.release_texture(final_tex);
+               }
+               in_warmup = false;
+       }
+
+       GLuint final_tex = compute_flow.exec(tex_gray, DISComputeFlow::FORWARD, DISComputeFlow::RESIZE_FLOW_TO_FULL_SIZE);
+       //GLuint final_tex = compute_flow.exec(tex_gray, DISComputeFlow::FORWARD_AND_BACKWARD, DISComputeFlow::RESIZE_FLOW_TO_FULL_SIZE);
 
        schedule_read<FlowType>(final_tex, width1, height1, filename0, filename1, flow_filename, "flow.ppm");
        compute_flow.release_texture(final_tex);
@@ -1780,8 +1837,7 @@ void compute_flow_only(int argc, char **argv, int optind)
                                filename0, width, height, width1, height1);
                        exit(1);
                }
-               gray.exec(tex0, tex0_gray, width, height);
-               glGenerateTextureMipmap(tex0_gray);
+               glCopyImageSubData(tex0, GL_TEXTURE_2D, 0, 0, 0, 0, image_tex, GL_TEXTURE_2D_ARRAY, 0, 0, 0, 0, width1, height1, 1);
                glDeleteTextures(1, &tex0);
 
                GLuint tex1 = load_texture(filename1, &width, &height, WITHOUT_MIPMAPS);
@@ -1790,17 +1846,18 @@ void compute_flow_only(int argc, char **argv, int optind)
                                filename1, width, height, width1, height1);
                        exit(1);
                }
-               gray.exec(tex1, tex1_gray, width, height);
-               glGenerateTextureMipmap(tex1_gray);
+               glCopyImageSubData(tex1, GL_TEXTURE_2D, 0, 0, 0, 0, image_tex, GL_TEXTURE_2D_ARRAY, 0, 0, 0, 1, width1, height1, 1);
                glDeleteTextures(1, &tex1);
 
-               GLuint final_tex = compute_flow.exec(tex0_gray, tex1_gray, DISComputeFlow::RESIZE_FLOW_TO_FULL_SIZE);
+               gray.exec(image_tex, tex_gray, width1, height1, /*num_layers=*/2);
+               glGenerateTextureMipmap(tex_gray);
+
+               GLuint final_tex = compute_flow.exec(tex_gray, DISComputeFlow::FORWARD, DISComputeFlow::RESIZE_FLOW_TO_FULL_SIZE);
 
                schedule_read<FlowType>(final_tex, width1, height1, filename0, filename1, flow_filename, "");
                compute_flow.release_texture(final_tex);
        }
-       glDeleteTextures(1, &tex0_gray);
-       glDeleteTextures(1, &tex1_gray);
+       glDeleteTextures(1, &tex_gray);
 
        while (!reads_in_progress.empty()) {
                finish_one_read<FlowType>(width1, height1);
@@ -1830,6 +1887,18 @@ void interpolate_image(int argc, char **argv, int optind)
                exit(1);
        }
 
+       // Move them into an array texture, since that's how the rest of the code
+       // would like them.
+       int levels = find_num_levels(width1, height1);
+       GLuint image_tex;
+       glCreateTextures(GL_TEXTURE_2D_ARRAY, 1, &image_tex);
+       glTextureStorage3D(image_tex, levels, GL_RGBA8, width1, height1, 2);
+       glCopyImageSubData(tex0, GL_TEXTURE_2D, 0, 0, 0, 0, image_tex, GL_TEXTURE_2D_ARRAY, 0, 0, 0, 0, width1, height1, 1);
+       glCopyImageSubData(tex1, GL_TEXTURE_2D, 0, 0, 0, 0, image_tex, GL_TEXTURE_2D_ARRAY, 0, 0, 0, 1, width1, height1, 1);
+       glDeleteTextures(1, &tex0);
+       glDeleteTextures(1, &tex1);
+       glGenerateTextureMipmap(image_tex);
+
        // Set up some PBOs to do asynchronous readback.
        GLuint pbos[5];
        glCreateBuffers(5, pbos);
@@ -1842,28 +1911,31 @@ void interpolate_image(int argc, char **argv, int optind)
        GrayscaleConversion gray;
        Interpolate interpolate(width1, height1, finest_level);
 
-       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 tex_gray;
+       glCreateTextures(GL_TEXTURE_2D_ARRAY, 1, &tex_gray);
+       glTextureStorage3D(tex_gray, levels, GL_R8, width1, height1, 2);
+       gray.exec(image_tex, tex_gray, width1, height1, /*num_layers=*/2);
+       glGenerateTextureMipmap(tex_gray);
+
+       if (enable_warmup) {
+               in_warmup = true;
+               for (int i = 0; i < 10; ++i) {
+                       GLuint bidirectional_flow_tex = compute_flow.exec(tex_gray, DISComputeFlow::FORWARD_AND_BACKWARD, DISComputeFlow::DO_NOT_RESIZE_FLOW);
+                       GLuint interpolated_tex = interpolate.exec(image_tex, bidirectional_flow_tex, width1, height1, 0.5f);
+                       compute_flow.release_texture(bidirectional_flow_tex);
+                       interpolate.release_texture(interpolated_tex);
+               }
+               in_warmup = false;
+       }
 
-       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);
+       GLuint bidirectional_flow_tex = compute_flow.exec(tex_gray, DISComputeFlow::FORWARD_AND_BACKWARD, DISComputeFlow::DO_NOT_RESIZE_FLOW);
 
        for (int frameno = 1; frameno < 60; ++frameno) {
                char ppm_filename[256];
                snprintf(ppm_filename, sizeof(ppm_filename), "interp%04d.ppm", frameno);
 
                float alpha = frameno / 60.0f;
-               GLuint interpolated_tex = interpolate.exec(tex0, tex1, forward_flow_tex, backward_flow_tex, width1, height1, alpha);
+               GLuint interpolated_tex = interpolate.exec(image_tex, bidirectional_flow_tex, width1, height1, alpha);
 
                schedule_read<RGBAType>(interpolated_tex, width1, height1, filename0, filename1, "", ppm_filename);
                interpolate.release_texture(interpolated_tex);
@@ -1883,7 +1955,8 @@ int main(int argc, char **argv)
                { "disable-timing", no_argument, 0, 1000 },
                { "detailed-timing", no_argument, 0, 1003 },
                { "ignore-variational-refinement", no_argument, 0, 1001 },  // Still calculates it, just doesn't apply it.
-               { "interpolate", no_argument, 0, 1002 }
+               { "interpolate", no_argument, 0, 1002 },
+               { "warmup", no_argument, 0, 1004 }
        };
 
        for ( ;; ) {
@@ -1915,6 +1988,9 @@ int main(int argc, char **argv)
                case 1003:
                        detailed_timing = true;
                        break;
+               case 1004:
+                       enable_warmup = true;
+                       break;
                default:
                        fprintf(stderr, "Unknown option '%s'\n", argv[option_index]);
                        exit(1);