git.sesse.net Git - nageru/blob - flow.cpp

   1 #define NO_SDL_GLEXT 1
   2
   3 #include <epoxy/gl.h>
   4
   5 #include <SDL2/SDL.h>
   6 #include <SDL2/SDL_error.h>
   7 #include <SDL2/SDL_events.h>
   8 #include <SDL2/SDL_image.h>
   9 #include <SDL2/SDL_keyboard.h>
  10 #include <SDL2/SDL_mouse.h>
  11 #include <SDL2/SDL_video.h>
  12
  13 #include <assert.h>
  14 #include <getopt.h>
  15 #include <stdio.h>
  16 #include <unistd.h>
  17
  18 #include "util.h"
  19
  20 #include <algorithm>
  21 #include <memory>
  22 #include <map>
  23 #include <vector>
  24
  25 #define BUFFER_OFFSET(i) ((char *)nullptr + (i))
  26
  27 using namespace std;
  28
  29 // Operating point 3 (10 Hz on CPU, excluding preprocessing).
  30 constexpr float patch_overlap_ratio = 0.75f;
  31 constexpr unsigned coarsest_level = 5;
  32 constexpr unsigned finest_level = 1;
  33 constexpr unsigned patch_size_pixels = 12;
  34
  35 // Weighting constants for the different parts of the variational refinement.
  36 // These don't correspond 1:1 to the values given in the DIS paper,
  37 // since we have different normalizations and ranges in some cases.
  38 float vr_gamma = 10.0f, vr_delta = 5.0f, vr_alpha = 10.0f;
  39
  40 // Some global OpenGL objects.
  41 // TODO: These should really be part of DISComputeFlow.
  42 GLuint nearest_sampler, linear_sampler, smoothness_sampler;
  43 GLuint vertex_vbo;
  44
  45 string read_file(const string &filename)
  46 {
  47         FILE *fp = fopen(filename.c_str(), "r");
  48         if (fp == nullptr) {
  49                 perror(filename.c_str());
  50                 exit(1);
  51         }
  52
  53         int ret = fseek(fp, 0, SEEK_END);
  54         if (ret == -1) {
  55                 perror("fseek(SEEK_END)");
  56                 exit(1);
  57         }
  58
  59         int size = ftell(fp);
  60
  61         ret = fseek(fp, 0, SEEK_SET);
  62         if (ret == -1) {
  63                 perror("fseek(SEEK_SET)");
  64                 exit(1);
  65         }
  66
  67         string str;
  68         str.resize(size);
  69         ret = fread(&str[0], size, 1, fp);
  70         if (ret == -1) {
  71                 perror("fread");
  72                 exit(1);
  73         }
  74         if (ret == 0) {
  75                 fprintf(stderr, "Short read when trying to read %d bytes from %s\n",
  76                                 size, filename.c_str());
  77                 exit(1);
  78         }
  79         fclose(fp);
  80
  81         return str;
  82 }
  83
  84
  85 GLuint compile_shader(const string &shader_src, GLenum type)
  86 {
  87         GLuint obj = glCreateShader(type);
  88         const GLchar* source[] = { shader_src.data() };
  89         const GLint length[] = { (GLint)shader_src.size() };
  90         glShaderSource(obj, 1, source, length);
  91         glCompileShader(obj);
  92
  93         GLchar info_log[4096];
  94         GLsizei log_length = sizeof(info_log) - 1;
  95         glGetShaderInfoLog(obj, log_length, &log_length, info_log);
  96         info_log[log_length] = 0;
  97         if (strlen(info_log) > 0) {
  98                 fprintf(stderr, "Shader compile log: %s\n", info_log);
  99         }
 100
 101         GLint status;
 102         glGetShaderiv(obj, GL_COMPILE_STATUS, &status);
 103         if (status == GL_FALSE) {
 104                 // Add some line numbers to easier identify compile errors.
 105                 string src_with_lines = "/*   1 */ ";
 106                 size_t lineno = 1;
 107                 for (char ch : shader_src) {
 108                         src_with_lines.push_back(ch);
 109                         if (ch == '\n') {
 110                                 char buf[32];
 111                                 snprintf(buf, sizeof(buf), "/* %3zu */ ", ++lineno);
 112                                 src_with_lines += buf;
 113                         }
 114                 }
 115
 116                 fprintf(stderr, "Failed to compile shader:\n%s\n", src_with_lines.c_str());
 117                 exit(1);
 118         }
 119
 120         return obj;
 121 }
 122
 123 GLuint load_texture(const char *filename, unsigned *width_ret, unsigned *height_ret)
 124 {
 125         SDL_Surface *surf = IMG_Load(filename);
 126         if (surf == nullptr) {
 127                 fprintf(stderr, "IMG_Load(%s): %s\n", filename, IMG_GetError());
 128                 exit(1);
 129         }
 130
 131         // For whatever reason, SDL doesn't support converting to YUV surfaces
 132         // nor grayscale, so we'll do it (slowly) ourselves.
 133         SDL_Surface *rgb_surf = SDL_ConvertSurfaceFormat(surf, SDL_PIXELFORMAT_RGBA8888, /*flags=*/0);
 134         if (rgb_surf == nullptr) {
 135                 fprintf(stderr, "SDL_ConvertSurfaceFormat(%s): %s\n", filename, SDL_GetError());
 136                 exit(1);
 137         }
 138
 139         SDL_FreeSurface(surf);
 140
 141         unsigned width = rgb_surf->w, height = rgb_surf->h;
 142         const uint8_t *sptr = (uint8_t *)rgb_surf->pixels;
 143         unique_ptr<uint8_t[]> pix(new uint8_t[width * height]);
 144
 145         // Extract the Y component, and convert to bottom-left origin.
 146         for (unsigned y = 0; y < height; ++y) {
 147                 unsigned y2 = height - 1 - y;
 148                 for (unsigned x = 0; x < width; ++x) {
 149                         uint8_t r = sptr[(y2 * width + x) * 4 + 3];
 150                         uint8_t g = sptr[(y2 * width + x) * 4 + 2];
 151                         uint8_t b = sptr[(y2 * width + x) * 4 + 1];
 152
 153                         // Rec. 709.
 154                         pix[y * width + x] = lrintf(r * 0.2126f + g * 0.7152f + b * 0.0722f);
 155                 }
 156         }
 157         SDL_FreeSurface(rgb_surf);
 158
 159         int levels = 1;
 160         for (int w = width, h = height; w > 1 || h > 1; ) {
 161                 w >>= 1;
 162                 h >>= 1;
 163                 ++levels;
 164         }
 165
 166         GLuint tex;
 167         glCreateTextures(GL_TEXTURE_2D, 1, &tex);
 168         glTextureStorage2D(tex, levels, GL_R8, width, height);
 169         glTextureSubImage2D(tex, 0, 0, 0, width, height, GL_RED, GL_UNSIGNED_BYTE, pix.get());
 170         glGenerateTextureMipmap(tex);
 171
 172         *width_ret = width;
 173         *height_ret = height;
 174
 175         return tex;
 176 }
 177
 178 GLuint link_program(GLuint vs_obj, GLuint fs_obj)
 179 {
 180         GLuint program = glCreateProgram();
 181         glAttachShader(program, vs_obj);
 182         glAttachShader(program, fs_obj);
 183         glLinkProgram(program);
 184         GLint success;
 185         glGetProgramiv(program, GL_LINK_STATUS, &success);
 186         if (success == GL_FALSE) {
 187                 GLchar error_log[1024] = {0};
 188                 glGetProgramInfoLog(program, 1024, nullptr, error_log);
 189                 fprintf(stderr, "Error linking program: %s\n", error_log);
 190                 exit(1);
 191         }
 192         return program;
 193 }
 194
 195 GLuint generate_vbo(GLint size, GLsizeiptr data_size, const GLvoid *data)
 196 {
 197         GLuint vbo;
 198         glCreateBuffers(1, &vbo);
 199         glBufferData(GL_ARRAY_BUFFER, data_size, data, GL_STATIC_DRAW);
 200         glNamedBufferData(vbo, data_size, data, GL_STATIC_DRAW);
 201         return vbo;
 202 }
 203
 204 GLuint fill_vertex_attribute(GLuint vao, GLuint glsl_program_num, const string &attribute_name, GLint size, GLenum type, GLsizeiptr data_size, const GLvoid *data)
 205 {
 206         int attrib = glGetAttribLocation(glsl_program_num, attribute_name.c_str());
 207         if (attrib == -1) {
 208                 return -1;
 209         }
 210
 211         GLuint vbo = generate_vbo(size, data_size, data);
 212
 213         glBindBuffer(GL_ARRAY_BUFFER, vbo);
 214         glEnableVertexArrayAttrib(vao, attrib);
 215         glVertexAttribPointer(attrib, size, type, GL_FALSE, 0, BUFFER_OFFSET(0));
 216         glBindBuffer(GL_ARRAY_BUFFER, 0);
 217
 218         return vbo;
 219 }
 220
 221 void bind_sampler(GLuint program, GLint location, GLuint texture_unit, GLuint tex, GLuint sampler)
 222 {
 223         if (location == -1) {
 224                 return;
 225         }
 226
 227         glBindTextureUnit(texture_unit, tex);
 228         glBindSampler(texture_unit, sampler);
 229         glProgramUniform1i(program, location, texture_unit);
 230 }
 231
 232 // A class that caches FBOs that render to a given set of textures.
 233 // It never frees anything, so it is only suitable for rendering to
 234 // the same (small) set of textures over and over again.
 235 template<size_t num_elements>
 236 class PersistentFBOSet {
 237 public:
 238         void render_to(const array<GLuint, num_elements> &textures);
 239
 240         // Convenience wrappers.
 241         void render_to(GLuint texture0, enable_if<num_elements == 1> * = nullptr) {
 242                 render_to({{texture0}});
 243         }
 244
 245         void render_to(GLuint texture0, GLuint texture1, enable_if<num_elements == 2> * = nullptr) {
 246                 render_to({{texture0, texture1}});
 247         }
 248
 249         void render_to(GLuint texture0, GLuint texture1, GLuint texture2, enable_if<num_elements == 3> * = nullptr) {
 250                 render_to({{texture0, texture1, texture2}});
 251         }
 252
 253         void render_to(GLuint texture0, GLuint texture1, GLuint texture2, GLuint texture3, enable_if<num_elements == 4> * = nullptr) {
 254                 render_to({{texture0, texture1, texture2, texture3}});
 255         }
 256
 257 private:
 258         // TODO: Delete these on destruction.
 259         map<array<GLuint, num_elements>, GLuint> fbos;
 260 };
 261
 262 template<size_t num_elements>
 263 void PersistentFBOSet<num_elements>::render_to(const array<GLuint, num_elements> &textures)
 264 {
 265         auto it = fbos.find(textures);
 266         if (it != fbos.end()) {
 267                 glBindFramebuffer(GL_FRAMEBUFFER, it->second);
 268                 return;
 269         }
 270
 271         GLuint fbo;
 272         glCreateFramebuffers(1, &fbo);
 273         GLenum bufs[num_elements];
 274         for (size_t i = 0; i < num_elements; ++i) {
 275                 glNamedFramebufferTexture(fbo, GL_COLOR_ATTACHMENT0 + i, textures[i], 0);
 276                 bufs[i] = GL_COLOR_ATTACHMENT0 + i;
 277         }
 278         glNamedFramebufferDrawBuffers(fbo, num_elements, bufs);
 279
 280         fbos[textures] = fbo;
 281         glBindFramebuffer(GL_FRAMEBUFFER, fbo);
 282 }
 283
 284 // Compute gradients in every point, used for the motion search.
 285 // The DIS paper doesn't actually mention how these are computed,
 286 // but seemingly, a 3x3 Sobel operator is used here (at least in
 287 // later versions of the code), while a [1 -8 0 8 -1] kernel is
 288 // used for all the derivatives in the variational refinement part
 289 // (which borrows code from DeepFlow). This is inconsistent,
 290 // but I guess we're better off with staying with the original
 291 // decisions until we actually know having different ones would be better.
 292 class Sobel {
 293 public:
 294         Sobel();
 295         void exec(GLint tex0_view, GLint grad0_tex, int level_width, int level_height);
 296
 297 private:
 298         PersistentFBOSet<1> fbos;
 299         GLuint sobel_vs_obj;
 300         GLuint sobel_fs_obj;
 301         GLuint sobel_program;
 302         GLuint sobel_vao;
 303
 304         GLuint uniform_tex, uniform_image_size;
 305 };
 306
 307 Sobel::Sobel()
 308 {
 309         sobel_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
 310         sobel_fs_obj = compile_shader(read_file("sobel.frag"), GL_FRAGMENT_SHADER);
 311         sobel_program = link_program(sobel_vs_obj, sobel_fs_obj);
 312
 313         // Set up the VAO containing all the required position/texcoord data.
 314         glCreateVertexArrays(1, &sobel_vao);
 315         glBindVertexArray(sobel_vao);
 316
 317         GLint position_attrib = glGetAttribLocation(sobel_program, "position");
 318         glEnableVertexArrayAttrib(sobel_vao, position_attrib);
 319         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 320
 321         uniform_tex = glGetUniformLocation(sobel_program, "tex");
 322 }
 323
 324 void Sobel::exec(GLint tex0_view, GLint grad0_tex, int level_width, int level_height)
 325 {
 326         glUseProgram(sobel_program);
 327         glBindTextureUnit(0, tex0_view);
 328         glBindSampler(0, nearest_sampler);
 329         glProgramUniform1i(sobel_program, uniform_tex, 0);
 330
 331         glViewport(0, 0, level_width, level_height);
 332         fbos.render_to(grad0_tex);
 333         glBindVertexArray(sobel_vao);
 334         glUseProgram(sobel_program);
 335         glDisable(GL_BLEND);
 336         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 337 }
 338
 339 // Motion search to find the initial flow. See motion_search.frag for documentation.
 340 class MotionSearch {
 341 public:
 342         MotionSearch();
 343         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);
 344
 345 private:
 346         PersistentFBOSet<1> fbos;
 347
 348         GLuint motion_vs_obj;
 349         GLuint motion_fs_obj;
 350         GLuint motion_search_program;
 351         GLuint motion_search_vao;
 352
 353         GLuint uniform_image_size, uniform_inv_image_size, uniform_inv_prev_level_size;
 354         GLuint uniform_image0_tex, uniform_image1_tex, uniform_grad0_tex, uniform_flow_tex;
 355 };
 356
 357 MotionSearch::MotionSearch()
 358 {
 359         motion_vs_obj = compile_shader(read_file("motion_search.vert"), GL_VERTEX_SHADER);
 360         motion_fs_obj = compile_shader(read_file("motion_search.frag"), GL_FRAGMENT_SHADER);
 361         motion_search_program = link_program(motion_vs_obj, motion_fs_obj);
 362
 363         // Set up the VAO containing all the required position/texcoord data.
 364         glCreateVertexArrays(1, &motion_search_vao);
 365         glBindVertexArray(motion_search_vao);
 366         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 367
 368         GLint position_attrib = glGetAttribLocation(motion_search_program, "position");
 369         glEnableVertexArrayAttrib(motion_search_vao, position_attrib);
 370         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 371
 372         uniform_image_size = glGetUniformLocation(motion_search_program, "image_size");
 373         uniform_inv_image_size = glGetUniformLocation(motion_search_program, "inv_image_size");
 374         uniform_inv_prev_level_size = glGetUniformLocation(motion_search_program, "inv_prev_level_size");
 375         uniform_image0_tex = glGetUniformLocation(motion_search_program, "image0_tex");
 376         uniform_image1_tex = glGetUniformLocation(motion_search_program, "image1_tex");
 377         uniform_grad0_tex = glGetUniformLocation(motion_search_program, "grad0_tex");
 378         uniform_flow_tex = glGetUniformLocation(motion_search_program, "flow_tex");
 379 }
 380
 381 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)
 382 {
 383         glUseProgram(motion_search_program);
 384
 385         bind_sampler(motion_search_program, uniform_image0_tex, 0, tex0_view, nearest_sampler);
 386         bind_sampler(motion_search_program, uniform_image1_tex, 1, tex1_view, linear_sampler);
 387         bind_sampler(motion_search_program, uniform_grad0_tex, 2, grad0_tex, nearest_sampler);
 388         bind_sampler(motion_search_program, uniform_flow_tex, 3, flow_tex, linear_sampler);
 389
 390         glProgramUniform2f(motion_search_program, uniform_image_size, level_width, level_height);
 391         glProgramUniform2f(motion_search_program, uniform_inv_image_size, 1.0f / level_width, 1.0f / level_height);
 392         glProgramUniform2f(motion_search_program, uniform_inv_prev_level_size, 1.0f / prev_level_width, 1.0f / prev_level_height);
 393
 394         glViewport(0, 0, width_patches, height_patches);
 395         fbos.render_to(flow_out_tex);
 396         glBindVertexArray(motion_search_vao);
 397         glUseProgram(motion_search_program);
 398         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 399 }
 400
 401 // Do “densification”, ie., upsampling of the flow patches to the flow field
 402 // (the same size as the image at this level). We draw one quad per patch
 403 // over its entire covered area (using instancing in the vertex shader),
 404 // and then weight the contributions in the pixel shader by post-warp difference.
 405 // This is equation (3) in the paper.
 406 //
 407 // We accumulate the flow vectors in the R/G channels (for u/v) and the total
 408 // weight in the B channel. Dividing R and G by B gives the normalized values.
 409 class Densify {
 410 public:
 411         Densify();
 412         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);
 413
 414 private:
 415         PersistentFBOSet<1> fbos;
 416
 417         GLuint densify_vs_obj;
 418         GLuint densify_fs_obj;
 419         GLuint densify_program;
 420         GLuint densify_vao;
 421
 422         GLuint uniform_width_patches, uniform_patch_size, uniform_patch_spacing;
 423         GLuint uniform_image0_tex, uniform_image1_tex, uniform_flow_tex;
 424 };
 425
 426 Densify::Densify()
 427 {
 428         densify_vs_obj = compile_shader(read_file("densify.vert"), GL_VERTEX_SHADER);
 429         densify_fs_obj = compile_shader(read_file("densify.frag"), GL_FRAGMENT_SHADER);
 430         densify_program = link_program(densify_vs_obj, densify_fs_obj);
 431
 432         // Set up the VAO containing all the required position/texcoord data.
 433         glCreateVertexArrays(1, &densify_vao);
 434         glBindVertexArray(densify_vao);
 435         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 436
 437         GLint position_attrib = glGetAttribLocation(densify_program, "position");
 438         glEnableVertexArrayAttrib(densify_vao, position_attrib);
 439         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 440
 441         uniform_width_patches = glGetUniformLocation(densify_program, "width_patches");
 442         uniform_patch_size = glGetUniformLocation(densify_program, "patch_size");
 443         uniform_patch_spacing = glGetUniformLocation(densify_program, "patch_spacing");
 444         uniform_image0_tex = glGetUniformLocation(densify_program, "image0_tex");
 445         uniform_image1_tex = glGetUniformLocation(densify_program, "image1_tex");
 446         uniform_flow_tex = glGetUniformLocation(densify_program, "flow_tex");
 447 }
 448
 449 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)
 450 {
 451         glUseProgram(densify_program);
 452
 453         bind_sampler(densify_program, uniform_image0_tex, 0, tex0_view, nearest_sampler);
 454         bind_sampler(densify_program, uniform_image1_tex, 1, tex1_view, linear_sampler);
 455         bind_sampler(densify_program, uniform_flow_tex, 2, flow_tex, nearest_sampler);
 456
 457         glProgramUniform1i(densify_program, uniform_width_patches, width_patches);
 458         glProgramUniform2f(densify_program, uniform_patch_size,
 459                 float(patch_size_pixels) / level_width,
 460                 float(patch_size_pixels) / level_height);
 461
 462         float patch_spacing_x = float(level_width - patch_size_pixels) / (width_patches - 1);
 463         float patch_spacing_y = float(level_height - patch_size_pixels) / (height_patches - 1);
 464         if (width_patches == 1) patch_spacing_x = 0.0f;  // Avoid infinities.
 465         if (height_patches == 1) patch_spacing_y = 0.0f;
 466         glProgramUniform2f(densify_program, uniform_patch_spacing,
 467                 patch_spacing_x / level_width,
 468                 patch_spacing_y / level_height);
 469
 470         glViewport(0, 0, level_width, level_height);
 471         glEnable(GL_BLEND);
 472         glBlendFunc(GL_ONE, GL_ONE);
 473         glBindVertexArray(densify_vao);
 474         fbos.render_to(dense_flow_tex);
 475         glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, width_patches * height_patches);
 476 }
 477
 478 // Warp I_1 to I_w, and then compute the mean (I) and difference (I_t) of
 479 // I_0 and I_w. The prewarping is what enables us to solve the variational
 480 // flow for du,dv instead of u,v.
 481 //
 482 // Also calculates the normalized flow, ie. divides by z (this is needed because
 483 // Densify works by additive blending) and multiplies by the image size.
 484 //
 485 // See variational_refinement.txt for more information.
 486 class Prewarp {
 487 public:
 488         Prewarp();
 489         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);
 490
 491 private:
 492         PersistentFBOSet<3> fbos;
 493
 494         GLuint prewarp_vs_obj;
 495         GLuint prewarp_fs_obj;
 496         GLuint prewarp_program;
 497         GLuint prewarp_vao;
 498
 499         GLuint uniform_image0_tex, uniform_image1_tex, uniform_flow_tex;
 500         GLuint uniform_image_size;
 501 };
 502
 503 Prewarp::Prewarp()
 504 {
 505         prewarp_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
 506         prewarp_fs_obj = compile_shader(read_file("prewarp.frag"), GL_FRAGMENT_SHADER);
 507         prewarp_program = link_program(prewarp_vs_obj, prewarp_fs_obj);
 508
 509         // Set up the VAO containing all the required position/texcoord data.
 510         glCreateVertexArrays(1, &prewarp_vao);
 511         glBindVertexArray(prewarp_vao);
 512         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 513
 514         GLint position_attrib = glGetAttribLocation(prewarp_program, "position");
 515         glEnableVertexArrayAttrib(prewarp_vao, position_attrib);
 516         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 517
 518         uniform_image0_tex = glGetUniformLocation(prewarp_program, "image0_tex");
 519         uniform_image1_tex = glGetUniformLocation(prewarp_program, "image1_tex");
 520         uniform_flow_tex = glGetUniformLocation(prewarp_program, "flow_tex");
 521
 522         uniform_image_size = glGetUniformLocation(prewarp_program, "image_size");
 523 }
 524
 525 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)
 526 {
 527         glUseProgram(prewarp_program);
 528
 529         bind_sampler(prewarp_program, uniform_image0_tex, 0, tex0_view, nearest_sampler);
 530         bind_sampler(prewarp_program, uniform_image1_tex, 1, tex1_view, linear_sampler);
 531         bind_sampler(prewarp_program, uniform_flow_tex, 2, flow_tex, nearest_sampler);
 532
 533         glProgramUniform2f(prewarp_program, uniform_image_size, level_width, level_height);
 534
 535         glViewport(0, 0, level_width, level_height);
 536         glDisable(GL_BLEND);
 537         glBindVertexArray(prewarp_vao);
 538         fbos.render_to(I_tex, I_t_tex, normalized_flow_tex);
 539         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 540 }
 541
 542 // From I, calculate the partial derivatives I_x and I_y. We use a four-tap
 543 // central difference filter, since apparently, that's tradition (I haven't
 544 // measured quality versus a more normal 0.5 (I[x+1] - I[x-1]).)
 545 // The coefficients come from
 546 //
 547 //   https://en.wikipedia.org/wiki/Finite_difference_coefficient
 548 //
 549 // Also computes β_0, since it depends only on I_x and I_y.
 550 class Derivatives {
 551 public:
 552         Derivatives();
 553         void exec(GLuint input_tex, GLuint I_x_y_tex, GLuint beta_0_tex, int level_width, int level_height);
 554
 555 private:
 556         PersistentFBOSet<2> fbos;
 557
 558         GLuint derivatives_vs_obj;
 559         GLuint derivatives_fs_obj;
 560         GLuint derivatives_program;
 561         GLuint derivatives_vao;
 562
 563         GLuint uniform_tex;
 564 };
 565
 566 Derivatives::Derivatives()
 567 {
 568         derivatives_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
 569         derivatives_fs_obj = compile_shader(read_file("derivatives.frag"), GL_FRAGMENT_SHADER);
 570         derivatives_program = link_program(derivatives_vs_obj, derivatives_fs_obj);
 571
 572         // Set up the VAO containing all the required position/texcoord data.
 573         glCreateVertexArrays(1, &derivatives_vao);
 574         glBindVertexArray(derivatives_vao);
 575         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 576
 577         GLint position_attrib = glGetAttribLocation(derivatives_program, "position");
 578         glEnableVertexArrayAttrib(derivatives_vao, position_attrib);
 579         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 580
 581         uniform_tex = glGetUniformLocation(derivatives_program, "tex");
 582 }
 583
 584 void Derivatives::exec(GLuint input_tex, GLuint I_x_y_tex, GLuint beta_0_tex, int level_width, int level_height)
 585 {
 586         glUseProgram(derivatives_program);
 587
 588         bind_sampler(derivatives_program, uniform_tex, 0, input_tex, nearest_sampler);
 589
 590         glViewport(0, 0, level_width, level_height);
 591         glDisable(GL_BLEND);
 592         glBindVertexArray(derivatives_vao);
 593         fbos.render_to(I_x_y_tex, beta_0_tex);
 594         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 595 }
 596
 597 // Calculate the smoothness constraints between neighboring pixels;
 598 // s_x(x,y) stores smoothness between pixel (x,y) and (x+1,y),
 599 // and s_y(x,y) stores between (x,y) and (x,y+1). We'll sample with
 600 // border color (0,0) later, so that there's zero diffusion out of
 601 // the border.
 602 //
 603 // See variational_refinement.txt for more information.
 604 class ComputeSmoothness {
 605 public:
 606         ComputeSmoothness();
 607         void exec(GLuint flow_tex, GLuint diff_flow_tex, GLuint smoothness_x_tex, GLuint smoothness_y_tex, int level_width, int level_height);
 608
 609 private:
 610         PersistentFBOSet<2> fbos;
 611
 612         GLuint smoothness_vs_obj;
 613         GLuint smoothness_fs_obj;
 614         GLuint smoothness_program;
 615         GLuint smoothness_vao;
 616
 617         GLuint uniform_flow_tex, uniform_diff_flow_tex;
 618         GLuint uniform_alpha;
 619 };
 620
 621 ComputeSmoothness::ComputeSmoothness()
 622 {
 623         smoothness_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
 624         smoothness_fs_obj = compile_shader(read_file("smoothness.frag"), GL_FRAGMENT_SHADER);
 625         smoothness_program = link_program(smoothness_vs_obj, smoothness_fs_obj);
 626
 627         // Set up the VAO containing all the required position/texcoord data.
 628         glCreateVertexArrays(1, &smoothness_vao);
 629         glBindVertexArray(smoothness_vao);
 630         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 631
 632         GLint position_attrib = glGetAttribLocation(smoothness_program, "position");
 633         glEnableVertexArrayAttrib(smoothness_vao, position_attrib);
 634         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 635
 636         uniform_flow_tex = glGetUniformLocation(smoothness_program, "flow_tex");
 637         uniform_diff_flow_tex = glGetUniformLocation(smoothness_program, "diff_flow_tex");
 638         uniform_alpha = glGetUniformLocation(smoothness_program, "alpha");
 639 }
 640
 641 void ComputeSmoothness::exec(GLuint flow_tex, GLuint diff_flow_tex, GLuint smoothness_x_tex, GLuint smoothness_y_tex, int level_width, int level_height)
 642 {
 643         glUseProgram(smoothness_program);
 644
 645         bind_sampler(smoothness_program, uniform_flow_tex, 0, flow_tex, nearest_sampler);
 646         bind_sampler(smoothness_program, uniform_diff_flow_tex, 1, diff_flow_tex, nearest_sampler);
 647         glProgramUniform1f(smoothness_program, uniform_alpha, vr_alpha);
 648
 649         glViewport(0, 0, level_width, level_height);
 650
 651         glDisable(GL_BLEND);
 652         glBindVertexArray(smoothness_vao);
 653         fbos.render_to(smoothness_x_tex, smoothness_y_tex);
 654         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 655
 656         // Make sure the smoothness on the right and upper borders is zero.
 657         // We could have done this by making (W-1)xH and Wx(H-1) textures instead
 658         // (we're sampling smoothness with all-zero border color), but we'd
 659         // have to adjust the sampling coordinates, which is annoying.
 660         glClearTexSubImage(smoothness_x_tex, 0,  level_width - 1, 0, 0,   1, level_height, 1,  GL_RED, GL_FLOAT, nullptr);
 661         glClearTexSubImage(smoothness_y_tex, 0,  0, level_height - 1, 0,  level_width, 1, 1,   GL_RED, GL_FLOAT, nullptr);
 662 }
 663
 664 // Set up the equations set (two equations in two unknowns, per pixel).
 665 // We store five floats; the three non-redundant elements of the 2x2 matrix (A)
 666 // as 32-bit floats, and the two elements on the right-hand side (b) as 16-bit
 667 // floats. (Actually, we store the inverse of the diagonal elements, because
 668 // we only ever need to divide by them.) This fits into four u32 values;
 669 // R, G, B for the matrix (the last element is symmetric) and A for the two b values.
 670 // All the values of the energy term (E_I, E_G, E_S), except the smoothness
 671 // terms that depend on other pixels, are calculated in one pass.
 672 //
 673 // See variational_refinement.txt for more information.
 674 class SetupEquations {
 675 public:
 676         SetupEquations();
 677         void exec(GLuint I_x_y_tex, GLuint I_t_tex, GLuint diff_flow_tex, GLuint flow_tex, GLuint beta_0_tex, GLuint smoothness_x_tex, GLuint smoothness_y_tex, GLuint equation_tex, int level_width, int level_height);
 678
 679 private:
 680         PersistentFBOSet<1> fbos;
 681
 682         GLuint equations_vs_obj;
 683         GLuint equations_fs_obj;
 684         GLuint equations_program;
 685         GLuint equations_vao;
 686
 687         GLuint uniform_I_x_y_tex, uniform_I_t_tex;
 688         GLuint uniform_diff_flow_tex, uniform_base_flow_tex;
 689         GLuint uniform_beta_0_tex;
 690         GLuint uniform_smoothness_x_tex, uniform_smoothness_y_tex;
 691         GLuint uniform_gamma, uniform_delta;
 692 };
 693
 694 SetupEquations::SetupEquations()
 695 {
 696         equations_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
 697         equations_fs_obj = compile_shader(read_file("equations.frag"), GL_FRAGMENT_SHADER);
 698         equations_program = link_program(equations_vs_obj, equations_fs_obj);
 699
 700         // Set up the VAO containing all the required position/texcoord data.
 701         glCreateVertexArrays(1, &equations_vao);
 702         glBindVertexArray(equations_vao);
 703         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 704
 705         GLint position_attrib = glGetAttribLocation(equations_program, "position");
 706         glEnableVertexArrayAttrib(equations_vao, position_attrib);
 707         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 708
 709         uniform_I_x_y_tex = glGetUniformLocation(equations_program, "I_x_y_tex");
 710         uniform_I_t_tex = glGetUniformLocation(equations_program, "I_t_tex");
 711         uniform_diff_flow_tex = glGetUniformLocation(equations_program, "diff_flow_tex");
 712         uniform_base_flow_tex = glGetUniformLocation(equations_program, "base_flow_tex");
 713         uniform_beta_0_tex = glGetUniformLocation(equations_program, "beta_0_tex");
 714         uniform_smoothness_x_tex = glGetUniformLocation(equations_program, "smoothness_x_tex");
 715         uniform_smoothness_y_tex = glGetUniformLocation(equations_program, "smoothness_y_tex");
 716         uniform_gamma = glGetUniformLocation(equations_program, "gamma");
 717         uniform_delta = glGetUniformLocation(equations_program, "delta");
 718 }
 719
 720 void SetupEquations::exec(GLuint I_x_y_tex, GLuint I_t_tex, GLuint diff_flow_tex, GLuint base_flow_tex, GLuint beta_0_tex, GLuint smoothness_x_tex, GLuint smoothness_y_tex, GLuint equation_tex, int level_width, int level_height)
 721 {
 722         glUseProgram(equations_program);
 723
 724         bind_sampler(equations_program, uniform_I_x_y_tex, 0, I_x_y_tex, nearest_sampler);
 725         bind_sampler(equations_program, uniform_I_t_tex, 1, I_t_tex, nearest_sampler);
 726         bind_sampler(equations_program, uniform_diff_flow_tex, 2, diff_flow_tex, nearest_sampler);
 727         bind_sampler(equations_program, uniform_base_flow_tex, 3, base_flow_tex, nearest_sampler);
 728         bind_sampler(equations_program, uniform_beta_0_tex, 4, beta_0_tex, nearest_sampler);
 729         bind_sampler(equations_program, uniform_smoothness_x_tex, 5, smoothness_x_tex, smoothness_sampler);
 730         bind_sampler(equations_program, uniform_smoothness_y_tex, 6, smoothness_y_tex, smoothness_sampler);
 731         glProgramUniform1f(equations_program, uniform_delta, vr_delta);
 732         glProgramUniform1f(equations_program, uniform_gamma, vr_gamma);
 733
 734         glViewport(0, 0, level_width, level_height);
 735         glDisable(GL_BLEND);
 736         glBindVertexArray(equations_vao);
 737         fbos.render_to(equation_tex);
 738         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 739 }
 740
 741 // Actually solve the equation sets made by SetupEquations, by means of
 742 // successive over-relaxation (SOR).
 743 //
 744 // See variational_refinement.txt for more information.
 745 class SOR {
 746 public:
 747         SOR();
 748         void exec(GLuint diff_flow_tex, GLuint equation_tex, GLuint smoothness_x_tex, GLuint smoothness_y_tex, int level_width, int level_height, int num_iterations);
 749
 750 private:
 751         PersistentFBOSet<1> fbos;
 752
 753         GLuint sor_vs_obj;
 754         GLuint sor_fs_obj;
 755         GLuint sor_program;
 756         GLuint sor_vao;
 757
 758         GLuint uniform_diff_flow_tex;
 759         GLuint uniform_equation_tex;
 760         GLuint uniform_smoothness_x_tex, uniform_smoothness_y_tex;
 761 };
 762
 763 SOR::SOR()
 764 {
 765         sor_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
 766         sor_fs_obj = compile_shader(read_file("sor.frag"), GL_FRAGMENT_SHADER);
 767         sor_program = link_program(sor_vs_obj, sor_fs_obj);
 768
 769         // Set up the VAO containing all the required position/texcoord data.
 770         glCreateVertexArrays(1, &sor_vao);
 771         glBindVertexArray(sor_vao);
 772         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 773
 774         GLint position_attrib = glGetAttribLocation(sor_program, "position");
 775         glEnableVertexArrayAttrib(sor_vao, position_attrib);
 776         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 777
 778         uniform_diff_flow_tex = glGetUniformLocation(sor_program, "diff_flow_tex");
 779         uniform_equation_tex = glGetUniformLocation(sor_program, "equation_tex");
 780         uniform_smoothness_x_tex = glGetUniformLocation(sor_program, "smoothness_x_tex");
 781         uniform_smoothness_y_tex = glGetUniformLocation(sor_program, "smoothness_y_tex");
 782 }
 783
 784 void SOR::exec(GLuint diff_flow_tex, GLuint equation_tex, GLuint smoothness_x_tex, GLuint smoothness_y_tex, int level_width, int level_height, int num_iterations)
 785 {
 786         glUseProgram(sor_program);
 787
 788         bind_sampler(sor_program, uniform_diff_flow_tex, 0, diff_flow_tex, nearest_sampler);
 789         bind_sampler(sor_program, uniform_smoothness_x_tex, 1, smoothness_x_tex, smoothness_sampler);
 790         bind_sampler(sor_program, uniform_smoothness_y_tex, 2, smoothness_y_tex, smoothness_sampler);
 791         bind_sampler(sor_program, uniform_equation_tex, 3, equation_tex, nearest_sampler);
 792
 793         glViewport(0, 0, level_width, level_height);
 794         glDisable(GL_BLEND);
 795         glBindVertexArray(sor_vao);
 796         fbos.render_to(diff_flow_tex);  // NOTE: Bind to same as we render from!
 797
 798         for (int i = 0; i < num_iterations; ++i) {
 799                 glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 800                 if (i != num_iterations - 1) {
 801                         glTextureBarrier();
 802                 }
 803         }
 804 }
 805
 806 // Simply add the differential flow found by the variational refinement to the base flow.
 807 // The output is in base_flow_tex; we don't need to make a new texture.
 808 class AddBaseFlow {
 809 public:
 810         AddBaseFlow();
 811         void exec(GLuint base_flow_tex, GLuint diff_flow_tex, int level_width, int level_height);
 812
 813 private:
 814         PersistentFBOSet<1> fbos;
 815
 816         GLuint add_flow_vs_obj;
 817         GLuint add_flow_fs_obj;
 818         GLuint add_flow_program;
 819         GLuint add_flow_vao;
 820
 821         GLuint uniform_diff_flow_tex;
 822 };
 823
 824 AddBaseFlow::AddBaseFlow()
 825 {
 826         add_flow_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
 827         add_flow_fs_obj = compile_shader(read_file("add_base_flow.frag"), GL_FRAGMENT_SHADER);
 828         add_flow_program = link_program(add_flow_vs_obj, add_flow_fs_obj);
 829
 830         // Set up the VAO containing all the required position/texcoord data.
 831         glCreateVertexArrays(1, &add_flow_vao);
 832         glBindVertexArray(add_flow_vao);
 833         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 834
 835         GLint position_attrib = glGetAttribLocation(add_flow_program, "position");
 836         glEnableVertexArrayAttrib(add_flow_vao, position_attrib);
 837         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 838
 839         uniform_diff_flow_tex = glGetUniformLocation(add_flow_program, "diff_flow_tex");
 840 }
 841
 842 void AddBaseFlow::exec(GLuint base_flow_tex, GLuint diff_flow_tex, int level_width, int level_height)
 843 {
 844         glUseProgram(add_flow_program);
 845
 846         bind_sampler(add_flow_program, uniform_diff_flow_tex, 0, diff_flow_tex, nearest_sampler);
 847
 848         glViewport(0, 0, level_width, level_height);
 849         glEnable(GL_BLEND);
 850         glBlendFunc(GL_ONE, GL_ONE);
 851         glBindVertexArray(add_flow_vao);
 852         fbos.render_to(base_flow_tex);
 853
 854         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 855 }
 856
 857 // Take a copy of the flow, bilinearly interpolated and scaled up.
 858 class ResizeFlow {
 859 public:
 860         ResizeFlow();
 861         void exec(GLuint in_tex, GLuint out_tex, int input_width, int input_height, int output_width, int output_height);
 862
 863 private:
 864         PersistentFBOSet<1> fbos;
 865
 866         GLuint resize_flow_vs_obj;
 867         GLuint resize_flow_fs_obj;
 868         GLuint resize_flow_program;
 869         GLuint resize_flow_vao;
 870
 871         GLuint uniform_flow_tex;
 872         GLuint uniform_scale_factor;
 873 };
 874
 875 ResizeFlow::ResizeFlow()
 876 {
 877         resize_flow_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
 878         resize_flow_fs_obj = compile_shader(read_file("resize_flow.frag"), GL_FRAGMENT_SHADER);
 879         resize_flow_program = link_program(resize_flow_vs_obj, resize_flow_fs_obj);
 880
 881         // Set up the VAO containing all the required position/texcoord data.
 882         glCreateVertexArrays(1, &resize_flow_vao);
 883         glBindVertexArray(resize_flow_vao);
 884         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 885
 886         GLint position_attrib = glGetAttribLocation(resize_flow_program, "position");
 887         glEnableVertexArrayAttrib(resize_flow_vao, position_attrib);
 888         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 889
 890         uniform_flow_tex = glGetUniformLocation(resize_flow_program, "flow_tex");
 891         uniform_scale_factor = glGetUniformLocation(resize_flow_program, "scale_factor");
 892 }
 893
 894 void ResizeFlow::exec(GLuint flow_tex, GLuint out_tex, int input_width, int input_height, int output_width, int output_height)
 895 {
 896         glUseProgram(resize_flow_program);
 897
 898         bind_sampler(resize_flow_program, uniform_flow_tex, 0, flow_tex, nearest_sampler);
 899
 900         glProgramUniform2f(resize_flow_program, uniform_scale_factor, float(output_width) / input_width, float(output_height) / input_height);
 901
 902         glViewport(0, 0, output_width, output_height);
 903         glDisable(GL_BLEND);
 904         glBindVertexArray(resize_flow_vao);
 905         fbos.render_to(out_tex);
 906
 907         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 908 }
 909
 910 class GPUTimers {
 911 public:
 912         void print();
 913         pair<GLuint, GLuint> begin_timer(const string &name, int level);
 914
 915 private:
 916         struct Timer {
 917                 string name;
 918                 int level;
 919                 pair<GLuint, GLuint> query;
 920         };
 921         vector<Timer> timers;
 922 };
 923
 924 pair<GLuint, GLuint> GPUTimers::begin_timer(const string &name, int level)
 925 {
 926         GLuint queries[2];
 927         glGenQueries(2, queries);
 928         glQueryCounter(queries[0], GL_TIMESTAMP);
 929
 930         Timer timer;
 931         timer.name = name;
 932         timer.level = level;
 933         timer.query.first = queries[0];
 934         timer.query.second = queries[1];
 935         timers.push_back(timer);
 936         return timer.query;
 937 }
 938
 939 void GPUTimers::print()
 940 {
 941         for (const Timer &timer : timers) {
 942                 // NOTE: This makes the CPU wait for the GPU.
 943                 GLuint64 time_start, time_end;
 944                 glGetQueryObjectui64v(timer.query.first, GL_QUERY_RESULT, &time_start);
 945                 glGetQueryObjectui64v(timer.query.second, GL_QUERY_RESULT, &time_end);
 946                 //fprintf(stderr, "GPU time used = %.1f ms\n", time_elapsed / 1e6);
 947                 for (int i = 0; i < timer.level * 2; ++i) {
 948                         fprintf(stderr, " ");
 949                 }
 950                 fprintf(stderr, "%-30s %4.1f ms\n", timer.name.c_str(), GLint64(time_end - time_start) / 1e6);
 951         }
 952 }
 953
 954 // A simple RAII class for timing until the end of the scope.
 955 class ScopedTimer {
 956 public:
 957         ScopedTimer(const string &name, GPUTimers *timers)
 958                 : timers(timers), level(0)
 959         {
 960                 query = timers->begin_timer(name, level);
 961         }
 962
 963         ScopedTimer(const string &name, ScopedTimer *parent_timer)
 964                 : timers(parent_timer->timers),
 965                   level(parent_timer->level + 1)
 966         {
 967                 query = timers->begin_timer(name, level);
 968         }
 969
 970         ~ScopedTimer()
 971         {
 972                 end();
 973         }
 974
 975         void end()
 976         {
 977                 if (!ended) {
 978                         glQueryCounter(query.second, GL_TIMESTAMP);
 979                         ended = true;
 980                 }
 981         }
 982
 983 private:
 984         GPUTimers *timers;
 985         int level;
 986         pair<GLuint, GLuint> query;
 987         bool ended = false;
 988 };
 989
 990 class DISComputeFlow {
 991 public:
 992         DISComputeFlow(int width, int height);
 993         GLuint exec(GLuint tex0, GLuint tex1);
 994
 995 private:
 996         int width, height;
 997         GLuint initial_flow_tex;
 998
 999         // The various passes.
1000         Sobel sobel;
1001         MotionSearch motion_search;
1002         Densify densify;
1003         Prewarp prewarp;
1004         Derivatives derivatives;
1005         ComputeSmoothness compute_smoothness;
1006         SetupEquations setup_equations;
1007         SOR sor;
1008         AddBaseFlow add_base_flow;
1009         ResizeFlow resize_flow;
1010 };
1011
1012 DISComputeFlow::DISComputeFlow(int width, int height)
1013         : width(width), height(height)
1014 {
1015         // Make some samplers.
1016         glCreateSamplers(1, &nearest_sampler);
1017         glSamplerParameteri(nearest_sampler, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
1018         glSamplerParameteri(nearest_sampler, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
1019         glSamplerParameteri(nearest_sampler, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
1020         glSamplerParameteri(nearest_sampler, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
1021
1022         glCreateSamplers(1, &linear_sampler);
1023         glSamplerParameteri(linear_sampler, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
1024         glSamplerParameteri(linear_sampler, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
1025         glSamplerParameteri(linear_sampler, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
1026         glSamplerParameteri(linear_sampler, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
1027
1028         // The smoothness is sampled so that once we get to a smoothness involving
1029         // a value outside the border, the diffusivity between the two becomes zero.
1030         glCreateSamplers(1, &smoothness_sampler);
1031         glSamplerParameteri(smoothness_sampler, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
1032         glSamplerParameteri(smoothness_sampler, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
1033         glSamplerParameteri(smoothness_sampler, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
1034         glSamplerParameteri(smoothness_sampler, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
1035         float zero[] = { 0.0f, 0.0f, 0.0f, 0.0f };
1036         glSamplerParameterfv(smoothness_sampler, GL_TEXTURE_BORDER_COLOR, zero);
1037
1038         // Initial flow is zero, 1x1.
1039         glCreateTextures(GL_TEXTURE_2D, 1, &initial_flow_tex);
1040         glTextureStorage2D(initial_flow_tex, 1, GL_RG16F, 1, 1);
1041         glClearTexImage(initial_flow_tex, 0, GL_RG, GL_FLOAT, nullptr);
1042 }
1043
1044 GLuint DISComputeFlow::exec(GLuint tex0, GLuint tex1)
1045 {
1046         int prev_level_width = 1, prev_level_height = 1;
1047         GLuint prev_level_flow_tex = initial_flow_tex;
1048
1049         GPUTimers timers;
1050
1051         ScopedTimer total_timer("Total", &timers);
1052         for (int level = coarsest_level; level >= int(finest_level); --level) {
1053                 char timer_name[256];
1054                 snprintf(timer_name, sizeof(timer_name), "Level %d", level);
1055                 ScopedTimer level_timer(timer_name, &total_timer);
1056
1057                 int level_width = width >> level;
1058                 int level_height = height >> level;
1059                 float patch_spacing_pixels = patch_size_pixels * (1.0f - patch_overlap_ratio);
1060                 int width_patches = 1 + lrintf((level_width - patch_size_pixels) / patch_spacing_pixels);
1061                 int height_patches = 1 + lrintf((level_height - patch_size_pixels) / patch_spacing_pixels);
1062
1063                 // Make sure we always read from the correct level; the chosen
1064                 // mipmapping could otherwise be rather unpredictable, especially
1065                 // during motion search.
1066                 // TODO: create these beforehand, and stop leaking them.
1067                 GLuint tex0_view, tex1_view;
1068                 glGenTextures(1, &tex0_view);
1069                 glTextureView(tex0_view, GL_TEXTURE_2D, tex0, GL_R8, level, 1, 0, 1);
1070                 glGenTextures(1, &tex1_view);
1071                 glTextureView(tex1_view, GL_TEXTURE_2D, tex1, GL_R8, level, 1, 0, 1);
1072
1073                 // Create a new texture; we could be fancy and render use a multi-level
1074                 // texture, but meh.
1075                 GLuint grad0_tex;
1076                 glCreateTextures(GL_TEXTURE_2D, 1, &grad0_tex);
1077                 glTextureStorage2D(grad0_tex, 1, GL_RG16F, level_width, level_height);
1078
1079                 // Find the derivative.
1080                 {
1081                         ScopedTimer timer("Sobel", &level_timer);
1082                         sobel.exec(tex0_view, grad0_tex, level_width, level_height);
1083                 }
1084
1085                 // Motion search to find the initial flow. We use the flow from the previous
1086                 // level (sampled bilinearly; no fancy tricks) as a guide, then search from there.
1087
1088                 // Create an output flow texture.
1089                 GLuint flow_out_tex;
1090                 glCreateTextures(GL_TEXTURE_2D, 1, &flow_out_tex);
1091                 glTextureStorage2D(flow_out_tex, 1, GL_RGB16F, width_patches, height_patches);
1092
1093                 // And draw.
1094                 {
1095                         ScopedTimer timer("Motion search", &level_timer);
1096                         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);
1097                 }
1098
1099                 // Densification.
1100
1101                 // Set up an output texture (initially zero).
1102                 GLuint dense_flow_tex;
1103                 glCreateTextures(GL_TEXTURE_2D, 1, &dense_flow_tex);
1104                 glTextureStorage2D(dense_flow_tex, 1, GL_RGB16F, level_width, level_height);
1105                 glClearTexImage(dense_flow_tex, 0, GL_RGB, GL_FLOAT, nullptr);
1106
1107                 // And draw.
1108                 {
1109                         ScopedTimer timer("Densification", &level_timer);
1110                         densify.exec(tex0_view, tex1_view, flow_out_tex, dense_flow_tex, level_width, level_height, width_patches, height_patches);
1111                 }
1112
1113                 // Everything below here in the loop belongs to variational refinement.
1114                 ScopedTimer varref_timer("Variational refinement", &level_timer);
1115
1116                 // Prewarping; create I and I_t, and a normalized base flow (so we don't
1117                 // have to normalize it over and over again, and also save some bandwidth).
1118                 //
1119                 // During the entire rest of the variational refinement, flow will be measured
1120                 // in pixels, not 0..1 normalized OpenGL texture coordinates.
1121                 // This is because variational refinement depends so heavily on derivatives,
1122                 // which are measured in intensity levels per pixel.
1123                 GLuint I_tex, I_t_tex, base_flow_tex;
1124                 glCreateTextures(GL_TEXTURE_2D, 1, &I_tex);
1125                 glCreateTextures(GL_TEXTURE_2D, 1, &I_t_tex);
1126                 glCreateTextures(GL_TEXTURE_2D, 1, &base_flow_tex);
1127                 glTextureStorage2D(I_tex, 1, GL_R16F, level_width, level_height);
1128                 glTextureStorage2D(I_t_tex, 1, GL_R16F, level_width, level_height);
1129                 glTextureStorage2D(base_flow_tex, 1, GL_RG16F, level_width, level_height);
1130                 {
1131                         ScopedTimer timer("Prewarping", &varref_timer);
1132                         prewarp.exec(tex0_view, tex1_view, dense_flow_tex, I_tex, I_t_tex, base_flow_tex, level_width, level_height);
1133                 }
1134
1135                 // Calculate I_x and I_y. We're only calculating first derivatives;
1136                 // the others will be taken on-the-fly in order to sample from fewer
1137                 // textures overall, since sampling from the L1 cache is cheap.
1138                 // (TODO: Verify that this is indeed faster than making separate
1139                 // double-derivative textures.)
1140                 GLuint I_x_y_tex, beta_0_tex;
1141                 glCreateTextures(GL_TEXTURE_2D, 1, &I_x_y_tex);
1142                 glCreateTextures(GL_TEXTURE_2D, 1, &beta_0_tex);
1143                 glTextureStorage2D(I_x_y_tex, 1, GL_RG16F, level_width, level_height);
1144                 glTextureStorage2D(beta_0_tex, 1, GL_R16F, level_width, level_height);
1145                 {
1146                         ScopedTimer timer("First derivatives", &varref_timer);
1147                         derivatives.exec(I_tex, I_x_y_tex, beta_0_tex, level_width, level_height);
1148                 }
1149
1150                 // We need somewhere to store du and dv (the flow increment, relative
1151                 // to the non-refined base flow u0 and v0). It starts at zero.
1152                 GLuint du_dv_tex;
1153                 glCreateTextures(GL_TEXTURE_2D, 1, &du_dv_tex);
1154                 glTextureStorage2D(du_dv_tex, 1, GL_RG16F, level_width, level_height);
1155                 glClearTexImage(du_dv_tex, 0, GL_RG, GL_FLOAT, nullptr);
1156
1157                 // And for smoothness.
1158                 GLuint smoothness_x_tex, smoothness_y_tex;
1159                 glCreateTextures(GL_TEXTURE_2D, 1, &smoothness_x_tex);
1160                 glCreateTextures(GL_TEXTURE_2D, 1, &smoothness_y_tex);
1161                 glTextureStorage2D(smoothness_x_tex, 1, GL_R16F, level_width, level_height);
1162                 glTextureStorage2D(smoothness_y_tex, 1, GL_R16F, level_width, level_height);
1163
1164                 // And finally for the equation set. See SetupEquations for
1165                 // the storage format.
1166                 GLuint equation_tex;
1167                 glCreateTextures(GL_TEXTURE_2D, 1, &equation_tex);
1168                 glTextureStorage2D(equation_tex, 1, GL_RGBA32UI, level_width, level_height);
1169
1170                 for (int outer_idx = 0; outer_idx < level + 1; ++outer_idx) {
1171                         // Calculate the smoothness terms between the neighboring pixels,
1172                         // both in x and y direction.
1173                         {
1174                                 ScopedTimer timer("Compute smoothness", &varref_timer);
1175                                 compute_smoothness.exec(base_flow_tex, du_dv_tex, smoothness_x_tex, smoothness_y_tex, level_width, level_height);
1176                         }
1177
1178                         // Set up the 2x2 equation system for each pixel.
1179                         {
1180                                 ScopedTimer timer("Set up equations", &varref_timer);
1181                                 setup_equations.exec(I_x_y_tex, I_t_tex, du_dv_tex, base_flow_tex, beta_0_tex, smoothness_x_tex, smoothness_y_tex, equation_tex, level_width, level_height);
1182                         }
1183
1184                         // Run a few SOR (or quasi-SOR, since we're not really Jacobi) iterations.
1185                         // Note that these are to/from the same texture.
1186                         {
1187                                 ScopedTimer timer("SOR", &varref_timer);
1188                                 sor.exec(du_dv_tex, equation_tex, smoothness_x_tex, smoothness_y_tex, level_width, level_height, 5);
1189                         }
1190                 }
1191
1192                 // Add the differential flow found by the variational refinement to the base flow,
1193                 // giving the final flow estimate for this level.
1194                 // The output is in diff_flow_tex; we don't need to make a new texture.
1195                 // You can comment out this part if you wish to test disabling of the variational refinement.
1196                 {
1197                         ScopedTimer timer("Add differential flow", &varref_timer);
1198                         add_base_flow.exec(base_flow_tex, du_dv_tex, level_width, level_height);
1199                 }
1200
1201                 prev_level_flow_tex = base_flow_tex;
1202                 prev_level_width = level_width;
1203                 prev_level_height = level_height;
1204         }
1205         total_timer.end();
1206
1207         timers.print();
1208
1209         // Scale up the flow to the final size (if needed).
1210         if (finest_level == 0) {
1211                 return prev_level_flow_tex;
1212         } else {
1213                 GLuint final_tex;
1214                 glCreateTextures(GL_TEXTURE_2D, 1, &final_tex);
1215                 glTextureStorage2D(final_tex, 1, GL_RG16F, width, height);
1216                 resize_flow.exec(prev_level_flow_tex, final_tex, prev_level_width, prev_level_height, width, height);
1217                 return final_tex;
1218         }
1219 }
1220
1221 int main(int argc, char **argv)
1222 {
1223         static const option long_options[] = {
1224                 { "alpha", required_argument, 0, 'a' },
1225                 { "delta", required_argument, 0, 'd' },
1226                 { "gamma", required_argument, 0, 'g' }
1227         };
1228
1229         for ( ;; ) {
1230                 int option_index = 0;
1231                 int c = getopt_long(argc, argv, "a:d:g:", long_options, &option_index);
1232
1233                 if (c == -1) {
1234                         break;
1235                 }
1236                 switch (c) {
1237                 case 'a':
1238                         vr_alpha = atof(optarg);
1239                         break;
1240                 case 'd':
1241                         vr_delta = atof(optarg);
1242                         break;
1243                 case 'g':
1244                         vr_gamma = atof(optarg);
1245                         break;
1246                 default:
1247                         fprintf(stderr, "Unknown option '%s'\n", argv[option_index]);
1248                         exit(1);
1249                 };
1250         }
1251
1252         if (SDL_Init(SDL_INIT_EVERYTHING) == -1) {
1253                 fprintf(stderr, "SDL_Init failed: %s\n", SDL_GetError());
1254                 exit(1);
1255         }
1256         SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);
1257         SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 0);
1258         SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 0);
1259         SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
1260
1261         SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
1262         SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4);
1263         SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 5);
1264         // SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_DEBUG_FLAG);
1265         SDL_Window *window = SDL_CreateWindow("OpenGL window",
1266                         SDL_WINDOWPOS_UNDEFINED,
1267                         SDL_WINDOWPOS_UNDEFINED,
1268                         64, 64,
1269                         SDL_WINDOW_OPENGL);
1270         SDL_GLContext context = SDL_GL_CreateContext(window);
1271         assert(context != nullptr);
1272
1273         // Load pictures.
1274         unsigned width1, height1, width2, height2;
1275         GLuint tex0 = load_texture(argc >= (optind + 1) ? argv[optind] : "test1499.png", &width1, &height1);
1276         GLuint tex1 = load_texture(argc >= (optind + 2) ? argv[optind + 1] : "test1500.png", &width2, &height2);
1277
1278         if (width1 != width2 || height1 != height2) {
1279                 fprintf(stderr, "Image dimensions don't match (%dx%d versus %dx%d)\n",
1280                         width1, height1, width2, height2);
1281                 exit(1);
1282         }
1283
1284         // FIXME: Should be part of DISComputeFlow (but needs to be initialized
1285         // before all the render passes).
1286         float vertices[] = {
1287                 0.0f, 1.0f,
1288                 0.0f, 0.0f,
1289                 1.0f, 1.0f,
1290                 1.0f, 0.0f,
1291         };
1292         glCreateBuffers(1, &vertex_vbo);
1293         glNamedBufferData(vertex_vbo, sizeof(vertices), vertices, GL_STATIC_DRAW);
1294         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
1295
1296         DISComputeFlow compute_flow(width1, height1);
1297         GLuint final_tex = compute_flow.exec(tex0, tex1);
1298
1299         unique_ptr<float[]> dense_flow(new float[width1 * height1 * 2]);
1300         glGetTextureImage(final_tex, 0, GL_RG, GL_FLOAT, width1 * height1 * 2 * sizeof(float), dense_flow.get());
1301
1302         FILE *fp = fopen("flow.ppm", "wb");
1303         FILE *flowfp = fopen("flow.flo", "wb");
1304         fprintf(fp, "P6\n%d %d\n255\n", width1, height1);
1305         fprintf(flowfp, "FEIH");
1306         fwrite(&width1, 4, 1, flowfp);
1307         fwrite(&height1, 4, 1, flowfp);
1308         for (unsigned y = 0; y < unsigned(height1); ++y) {
1309                 int yy = height1 - y - 1;
1310                 for (unsigned x = 0; x < unsigned(width1); ++x) {
1311                         float du = dense_flow[(yy * width1 + x) * 2 + 0];
1312                         float dv = dense_flow[(yy * width1 + x) * 2 + 1];
1313
1314                         dv = -dv;
1315
1316                         fwrite(&du, 4, 1, flowfp);
1317                         fwrite(&dv, 4, 1, flowfp);
1318
1319                         uint8_t r, g, b;
1320                         flow2rgb(du, dv, &r, &g, &b);
1321                         putc(r, fp);
1322                         putc(g, fp);
1323                         putc(b, fp);
1324                 }
1325         }
1326         fclose(fp);
1327         fclose(flowfp);
1328
1329         fprintf(stderr, "err = %d\n", glGetError());
1330 }