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 <deque>
  22 #include <memory>
  23 #include <map>
  24 #include <stack>
  25 #include <vector>
  26
  27 #define BUFFER_OFFSET(i) ((char *)nullptr + (i))
  28
  29 using namespace std;
  30
  31 // Operating point 3 (10 Hz on CPU, excluding preprocessing).
  32 constexpr float patch_overlap_ratio = 0.75f;
  33 constexpr unsigned coarsest_level = 5;
  34 constexpr unsigned finest_level = 1;
  35 constexpr unsigned patch_size_pixels = 12;
  36
  37 // Weighting constants for the different parts of the variational refinement.
  38 // These don't correspond 1:1 to the values given in the DIS paper,
  39 // since we have different normalizations and ranges in some cases.
  40 float vr_gamma = 10.0f, vr_delta = 5.0f, vr_alpha = 10.0f;
  41
  42 bool enable_timing = true;
  43 bool enable_variational_refinement = true;  // Just for debugging.
  44
  45 // Some global OpenGL objects.
  46 // TODO: These should really be part of DISComputeFlow.
  47 GLuint nearest_sampler, linear_sampler, smoothness_sampler;
  48 GLuint vertex_vbo;
  49
  50 // Structures for asynchronous readback. We assume everything is the same size (and GL_RG16F).
  51 struct ReadInProgress {
  52         GLuint pbo;
  53         string filename0, filename1;
  54         string flow_filename, ppm_filename;  // Either may be empty for no write.
  55 };
  56 stack<GLuint> spare_pbos;
  57 deque<ReadInProgress> reads_in_progress;
  58
  59 string read_file(const string &filename)
  60 {
  61         FILE *fp = fopen(filename.c_str(), "r");
  62         if (fp == nullptr) {
  63                 perror(filename.c_str());
  64                 exit(1);
  65         }
  66
  67         int ret = fseek(fp, 0, SEEK_END);
  68         if (ret == -1) {
  69                 perror("fseek(SEEK_END)");
  70                 exit(1);
  71         }
  72
  73         int size = ftell(fp);
  74
  75         ret = fseek(fp, 0, SEEK_SET);
  76         if (ret == -1) {
  77                 perror("fseek(SEEK_SET)");
  78                 exit(1);
  79         }
  80
  81         string str;
  82         str.resize(size);
  83         ret = fread(&str[0], size, 1, fp);
  84         if (ret == -1) {
  85                 perror("fread");
  86                 exit(1);
  87         }
  88         if (ret == 0) {
  89                 fprintf(stderr, "Short read when trying to read %d bytes from %s\n",
  90                                 size, filename.c_str());
  91                 exit(1);
  92         }
  93         fclose(fp);
  94
  95         return str;
  96 }
  97
  98
  99 GLuint compile_shader(const string &shader_src, GLenum type)
 100 {
 101         GLuint obj = glCreateShader(type);
 102         const GLchar* source[] = { shader_src.data() };
 103         const GLint length[] = { (GLint)shader_src.size() };
 104         glShaderSource(obj, 1, source, length);
 105         glCompileShader(obj);
 106
 107         GLchar info_log[4096];
 108         GLsizei log_length = sizeof(info_log) - 1;
 109         glGetShaderInfoLog(obj, log_length, &log_length, info_log);
 110         info_log[log_length] = 0;
 111         if (strlen(info_log) > 0) {
 112                 fprintf(stderr, "Shader compile log: %s\n", info_log);
 113         }
 114
 115         GLint status;
 116         glGetShaderiv(obj, GL_COMPILE_STATUS, &status);
 117         if (status == GL_FALSE) {
 118                 // Add some line numbers to easier identify compile errors.
 119                 string src_with_lines = "/*   1 */ ";
 120                 size_t lineno = 1;
 121                 for (char ch : shader_src) {
 122                         src_with_lines.push_back(ch);
 123                         if (ch == '\n') {
 124                                 char buf[32];
 125                                 snprintf(buf, sizeof(buf), "/* %3zu */ ", ++lineno);
 126                                 src_with_lines += buf;
 127                         }
 128                 }
 129
 130                 fprintf(stderr, "Failed to compile shader:\n%s\n", src_with_lines.c_str());
 131                 exit(1);
 132         }
 133
 134         return obj;
 135 }
 136
 137 GLuint load_texture(const char *filename, unsigned *width_ret, unsigned *height_ret)
 138 {
 139         SDL_Surface *surf = IMG_Load(filename);
 140         if (surf == nullptr) {
 141                 fprintf(stderr, "IMG_Load(%s): %s\n", filename, IMG_GetError());
 142                 exit(1);
 143         }
 144
 145         // For whatever reason, SDL doesn't support converting to YUV surfaces
 146         // nor grayscale, so we'll do it (slowly) ourselves.
 147         SDL_Surface *rgb_surf = SDL_ConvertSurfaceFormat(surf, SDL_PIXELFORMAT_RGBA8888, /*flags=*/0);
 148         if (rgb_surf == nullptr) {
 149                 fprintf(stderr, "SDL_ConvertSurfaceFormat(%s): %s\n", filename, SDL_GetError());
 150                 exit(1);
 151         }
 152
 153         SDL_FreeSurface(surf);
 154
 155         unsigned width = rgb_surf->w, height = rgb_surf->h;
 156         const uint8_t *sptr = (uint8_t *)rgb_surf->pixels;
 157         unique_ptr<uint8_t[]> pix(new uint8_t[width * height]);
 158
 159         // Extract the Y component, and convert to bottom-left origin.
 160         for (unsigned y = 0; y < height; ++y) {
 161                 unsigned y2 = height - 1 - y;
 162                 for (unsigned x = 0; x < width; ++x) {
 163                         uint8_t r = sptr[(y2 * width + x) * 4 + 3];
 164                         uint8_t g = sptr[(y2 * width + x) * 4 + 2];
 165                         uint8_t b = sptr[(y2 * width + x) * 4 + 1];
 166
 167                         // Rec. 709.
 168                         pix[y * width + x] = lrintf(r * 0.2126f + g * 0.7152f + b * 0.0722f);
 169                 }
 170         }
 171         SDL_FreeSurface(rgb_surf);
 172
 173         int levels = 1;
 174         for (int w = width, h = height; w > 1 || h > 1; ) {
 175                 w >>= 1;
 176                 h >>= 1;
 177                 ++levels;
 178         }
 179
 180         GLuint tex;
 181         glCreateTextures(GL_TEXTURE_2D, 1, &tex);
 182         glTextureStorage2D(tex, levels, GL_R8, width, height);
 183         glTextureSubImage2D(tex, 0, 0, 0, width, height, GL_RED, GL_UNSIGNED_BYTE, pix.get());
 184         glGenerateTextureMipmap(tex);
 185
 186         *width_ret = width;
 187         *height_ret = height;
 188
 189         return tex;
 190 }
 191
 192 GLuint link_program(GLuint vs_obj, GLuint fs_obj)
 193 {
 194         GLuint program = glCreateProgram();
 195         glAttachShader(program, vs_obj);
 196         glAttachShader(program, fs_obj);
 197         glLinkProgram(program);
 198         GLint success;
 199         glGetProgramiv(program, GL_LINK_STATUS, &success);
 200         if (success == GL_FALSE) {
 201                 GLchar error_log[1024] = {0};
 202                 glGetProgramInfoLog(program, 1024, nullptr, error_log);
 203                 fprintf(stderr, "Error linking program: %s\n", error_log);
 204                 exit(1);
 205         }
 206         return program;
 207 }
 208
 209 GLuint generate_vbo(GLint size, GLsizeiptr data_size, const GLvoid *data)
 210 {
 211         GLuint vbo;
 212         glCreateBuffers(1, &vbo);
 213         glBufferData(GL_ARRAY_BUFFER, data_size, data, GL_STATIC_DRAW);
 214         glNamedBufferData(vbo, data_size, data, GL_STATIC_DRAW);
 215         return vbo;
 216 }
 217
 218 GLuint fill_vertex_attribute(GLuint vao, GLuint glsl_program_num, const string &attribute_name, GLint size, GLenum type, GLsizeiptr data_size, const GLvoid *data)
 219 {
 220         int attrib = glGetAttribLocation(glsl_program_num, attribute_name.c_str());
 221         if (attrib == -1) {
 222                 return -1;
 223         }
 224
 225         GLuint vbo = generate_vbo(size, data_size, data);
 226
 227         glBindBuffer(GL_ARRAY_BUFFER, vbo);
 228         glEnableVertexArrayAttrib(vao, attrib);
 229         glVertexAttribPointer(attrib, size, type, GL_FALSE, 0, BUFFER_OFFSET(0));
 230         glBindBuffer(GL_ARRAY_BUFFER, 0);
 231
 232         return vbo;
 233 }
 234
 235 void bind_sampler(GLuint program, GLint location, GLuint texture_unit, GLuint tex, GLuint sampler)
 236 {
 237         if (location == -1) {
 238                 return;
 239         }
 240
 241         glBindTextureUnit(texture_unit, tex);
 242         glBindSampler(texture_unit, sampler);
 243         glProgramUniform1i(program, location, texture_unit);
 244 }
 245
 246 // A class that caches FBOs that render to a given set of textures.
 247 // It never frees anything, so it is only suitable for rendering to
 248 // the same (small) set of textures over and over again.
 249 template<size_t num_elements>
 250 class PersistentFBOSet {
 251 public:
 252         void render_to(const array<GLuint, num_elements> &textures);
 253
 254         // Convenience wrappers.
 255         void render_to(GLuint texture0, enable_if<num_elements == 1> * = nullptr) {
 256                 render_to({{texture0}});
 257         }
 258
 259         void render_to(GLuint texture0, GLuint texture1, enable_if<num_elements == 2> * = nullptr) {
 260                 render_to({{texture0, texture1}});
 261         }
 262
 263         void render_to(GLuint texture0, GLuint texture1, GLuint texture2, enable_if<num_elements == 3> * = nullptr) {
 264                 render_to({{texture0, texture1, texture2}});
 265         }
 266
 267         void render_to(GLuint texture0, GLuint texture1, GLuint texture2, GLuint texture3, enable_if<num_elements == 4> * = nullptr) {
 268                 render_to({{texture0, texture1, texture2, texture3}});
 269         }
 270
 271 private:
 272         // TODO: Delete these on destruction.
 273         map<array<GLuint, num_elements>, GLuint> fbos;
 274 };
 275
 276 template<size_t num_elements>
 277 void PersistentFBOSet<num_elements>::render_to(const array<GLuint, num_elements> &textures)
 278 {
 279         auto it = fbos.find(textures);
 280         if (it != fbos.end()) {
 281                 glBindFramebuffer(GL_FRAMEBUFFER, it->second);
 282                 return;
 283         }
 284
 285         GLuint fbo;
 286         glCreateFramebuffers(1, &fbo);
 287         GLenum bufs[num_elements];
 288         for (size_t i = 0; i < num_elements; ++i) {
 289                 glNamedFramebufferTexture(fbo, GL_COLOR_ATTACHMENT0 + i, textures[i], 0);
 290                 bufs[i] = GL_COLOR_ATTACHMENT0 + i;
 291         }
 292         glNamedFramebufferDrawBuffers(fbo, num_elements, bufs);
 293
 294         fbos[textures] = fbo;
 295         glBindFramebuffer(GL_FRAMEBUFFER, fbo);
 296 }
 297
 298 // Compute gradients in every point, used for the motion search.
 299 // The DIS paper doesn't actually mention how these are computed,
 300 // but seemingly, a 3x3 Sobel operator is used here (at least in
 301 // later versions of the code), while a [1 -8 0 8 -1] kernel is
 302 // used for all the derivatives in the variational refinement part
 303 // (which borrows code from DeepFlow). This is inconsistent,
 304 // but I guess we're better off with staying with the original
 305 // decisions until we actually know having different ones would be better.
 306 class Sobel {
 307 public:
 308         Sobel();
 309         void exec(GLint tex0_view, GLint grad0_tex, int level_width, int level_height);
 310
 311 private:
 312         PersistentFBOSet<1> fbos;
 313         GLuint sobel_vs_obj;
 314         GLuint sobel_fs_obj;
 315         GLuint sobel_program;
 316         GLuint sobel_vao;
 317
 318         GLuint uniform_tex, uniform_image_size;
 319 };
 320
 321 Sobel::Sobel()
 322 {
 323         sobel_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
 324         sobel_fs_obj = compile_shader(read_file("sobel.frag"), GL_FRAGMENT_SHADER);
 325         sobel_program = link_program(sobel_vs_obj, sobel_fs_obj);
 326
 327         // Set up the VAO containing all the required position/texcoord data.
 328         glCreateVertexArrays(1, &sobel_vao);
 329         glBindVertexArray(sobel_vao);
 330
 331         GLint position_attrib = glGetAttribLocation(sobel_program, "position");
 332         glEnableVertexArrayAttrib(sobel_vao, position_attrib);
 333         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 334
 335         uniform_tex = glGetUniformLocation(sobel_program, "tex");
 336 }
 337
 338 void Sobel::exec(GLint tex0_view, GLint grad0_tex, int level_width, int level_height)
 339 {
 340         glUseProgram(sobel_program);
 341         glBindTextureUnit(0, tex0_view);
 342         glBindSampler(0, nearest_sampler);
 343         glProgramUniform1i(sobel_program, uniform_tex, 0);
 344
 345         glViewport(0, 0, level_width, level_height);
 346         fbos.render_to(grad0_tex);
 347         glBindVertexArray(sobel_vao);
 348         glUseProgram(sobel_program);
 349         glDisable(GL_BLEND);
 350         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 351 }
 352
 353 // Motion search to find the initial flow. See motion_search.frag for documentation.
 354 class MotionSearch {
 355 public:
 356         MotionSearch();
 357         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);
 358
 359 private:
 360         PersistentFBOSet<1> fbos;
 361
 362         GLuint motion_vs_obj;
 363         GLuint motion_fs_obj;
 364         GLuint motion_search_program;
 365         GLuint motion_search_vao;
 366
 367         GLuint uniform_image_size, uniform_inv_image_size, uniform_inv_flow_size, uniform_inv_prev_level_size;
 368         GLuint uniform_image0_tex, uniform_image1_tex, uniform_grad0_tex, uniform_flow_tex;
 369 };
 370
 371 MotionSearch::MotionSearch()
 372 {
 373         motion_vs_obj = compile_shader(read_file("motion_search.vert"), GL_VERTEX_SHADER);
 374         motion_fs_obj = compile_shader(read_file("motion_search.frag"), GL_FRAGMENT_SHADER);
 375         motion_search_program = link_program(motion_vs_obj, motion_fs_obj);
 376
 377         // Set up the VAO containing all the required position/texcoord data.
 378         glCreateVertexArrays(1, &motion_search_vao);
 379         glBindVertexArray(motion_search_vao);
 380         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 381
 382         GLint position_attrib = glGetAttribLocation(motion_search_program, "position");
 383         glEnableVertexArrayAttrib(motion_search_vao, position_attrib);
 384         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 385
 386         uniform_image_size = glGetUniformLocation(motion_search_program, "image_size");
 387         uniform_inv_image_size = glGetUniformLocation(motion_search_program, "inv_image_size");
 388         uniform_inv_flow_size = glGetUniformLocation(motion_search_program, "inv_flow_size");
 389         uniform_inv_prev_level_size = glGetUniformLocation(motion_search_program, "inv_prev_level_size");
 390         uniform_image0_tex = glGetUniformLocation(motion_search_program, "image0_tex");
 391         uniform_image1_tex = glGetUniformLocation(motion_search_program, "image1_tex");
 392         uniform_grad0_tex = glGetUniformLocation(motion_search_program, "grad0_tex");
 393         uniform_flow_tex = glGetUniformLocation(motion_search_program, "flow_tex");
 394 }
 395
 396 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)
 397 {
 398         glUseProgram(motion_search_program);
 399
 400         bind_sampler(motion_search_program, uniform_image0_tex, 0, tex0_view, nearest_sampler);
 401         bind_sampler(motion_search_program, uniform_image1_tex, 1, tex1_view, linear_sampler);
 402         bind_sampler(motion_search_program, uniform_grad0_tex, 2, grad0_tex, nearest_sampler);
 403         bind_sampler(motion_search_program, uniform_flow_tex, 3, flow_tex, linear_sampler);
 404
 405         glProgramUniform2f(motion_search_program, uniform_image_size, level_width, level_height);
 406         glProgramUniform2f(motion_search_program, uniform_inv_image_size, 1.0f / level_width, 1.0f / level_height);
 407         glProgramUniform2f(motion_search_program, uniform_inv_flow_size, 1.0f / width_patches, 1.0f / height_patches);
 408         glProgramUniform2f(motion_search_program, uniform_inv_prev_level_size, 1.0f / prev_level_width, 1.0f / prev_level_height);
 409
 410         glViewport(0, 0, width_patches, height_patches);
 411         fbos.render_to(flow_out_tex);
 412         glBindVertexArray(motion_search_vao);
 413         glUseProgram(motion_search_program);
 414         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 415 }
 416
 417 // Do “densification”, ie., upsampling of the flow patches to the flow field
 418 // (the same size as the image at this level). We draw one quad per patch
 419 // over its entire covered area (using instancing in the vertex shader),
 420 // and then weight the contributions in the pixel shader by post-warp difference.
 421 // This is equation (3) in the paper.
 422 //
 423 // We accumulate the flow vectors in the R/G channels (for u/v) and the total
 424 // weight in the B channel. Dividing R and G by B gives the normalized values.
 425 class Densify {
 426 public:
 427         Densify();
 428         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);
 429
 430 private:
 431         PersistentFBOSet<1> fbos;
 432
 433         GLuint densify_vs_obj;
 434         GLuint densify_fs_obj;
 435         GLuint densify_program;
 436         GLuint densify_vao;
 437
 438         GLuint uniform_width_patches, uniform_patch_size, uniform_patch_spacing;
 439         GLuint uniform_image0_tex, uniform_image1_tex, uniform_flow_tex;
 440 };
 441
 442 Densify::Densify()
 443 {
 444         densify_vs_obj = compile_shader(read_file("densify.vert"), GL_VERTEX_SHADER);
 445         densify_fs_obj = compile_shader(read_file("densify.frag"), GL_FRAGMENT_SHADER);
 446         densify_program = link_program(densify_vs_obj, densify_fs_obj);
 447
 448         // Set up the VAO containing all the required position/texcoord data.
 449         glCreateVertexArrays(1, &densify_vao);
 450         glBindVertexArray(densify_vao);
 451         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 452
 453         GLint position_attrib = glGetAttribLocation(densify_program, "position");
 454         glEnableVertexArrayAttrib(densify_vao, position_attrib);
 455         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 456
 457         uniform_width_patches = glGetUniformLocation(densify_program, "width_patches");
 458         uniform_patch_size = glGetUniformLocation(densify_program, "patch_size");
 459         uniform_patch_spacing = glGetUniformLocation(densify_program, "patch_spacing");
 460         uniform_image0_tex = glGetUniformLocation(densify_program, "image0_tex");
 461         uniform_image1_tex = glGetUniformLocation(densify_program, "image1_tex");
 462         uniform_flow_tex = glGetUniformLocation(densify_program, "flow_tex");
 463 }
 464
 465 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)
 466 {
 467         glUseProgram(densify_program);
 468
 469         bind_sampler(densify_program, uniform_image0_tex, 0, tex0_view, nearest_sampler);
 470         bind_sampler(densify_program, uniform_image1_tex, 1, tex1_view, linear_sampler);
 471         bind_sampler(densify_program, uniform_flow_tex, 2, flow_tex, nearest_sampler);
 472
 473         glProgramUniform1i(densify_program, uniform_width_patches, width_patches);
 474         glProgramUniform2f(densify_program, uniform_patch_size,
 475                 float(patch_size_pixels) / level_width,
 476                 float(patch_size_pixels) / level_height);
 477
 478         float patch_spacing_x = float(level_width - patch_size_pixels) / (width_patches - 1);
 479         float patch_spacing_y = float(level_height - patch_size_pixels) / (height_patches - 1);
 480         if (width_patches == 1) patch_spacing_x = 0.0f;  // Avoid infinities.
 481         if (height_patches == 1) patch_spacing_y = 0.0f;
 482         glProgramUniform2f(densify_program, uniform_patch_spacing,
 483                 patch_spacing_x / level_width,
 484                 patch_spacing_y / level_height);
 485
 486         glViewport(0, 0, level_width, level_height);
 487         glEnable(GL_BLEND);
 488         glBlendFunc(GL_ONE, GL_ONE);
 489         glBindVertexArray(densify_vao);
 490         fbos.render_to(dense_flow_tex);
 491         glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, width_patches * height_patches);
 492 }
 493
 494 // Warp I_1 to I_w, and then compute the mean (I) and difference (I_t) of
 495 // I_0 and I_w. The prewarping is what enables us to solve the variational
 496 // flow for du,dv instead of u,v.
 497 //
 498 // Also calculates the normalized flow, ie. divides by z (this is needed because
 499 // Densify works by additive blending) and multiplies by the image size.
 500 //
 501 // See variational_refinement.txt for more information.
 502 class Prewarp {
 503 public:
 504         Prewarp();
 505         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);
 506
 507 private:
 508         PersistentFBOSet<3> fbos;
 509
 510         GLuint prewarp_vs_obj;
 511         GLuint prewarp_fs_obj;
 512         GLuint prewarp_program;
 513         GLuint prewarp_vao;
 514
 515         GLuint uniform_image0_tex, uniform_image1_tex, uniform_flow_tex;
 516         GLuint uniform_image_size;
 517 };
 518
 519 Prewarp::Prewarp()
 520 {
 521         prewarp_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
 522         prewarp_fs_obj = compile_shader(read_file("prewarp.frag"), GL_FRAGMENT_SHADER);
 523         prewarp_program = link_program(prewarp_vs_obj, prewarp_fs_obj);
 524
 525         // Set up the VAO containing all the required position/texcoord data.
 526         glCreateVertexArrays(1, &prewarp_vao);
 527         glBindVertexArray(prewarp_vao);
 528         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 529
 530         GLint position_attrib = glGetAttribLocation(prewarp_program, "position");
 531         glEnableVertexArrayAttrib(prewarp_vao, position_attrib);
 532         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 533
 534         uniform_image0_tex = glGetUniformLocation(prewarp_program, "image0_tex");
 535         uniform_image1_tex = glGetUniformLocation(prewarp_program, "image1_tex");
 536         uniform_flow_tex = glGetUniformLocation(prewarp_program, "flow_tex");
 537
 538         uniform_image_size = glGetUniformLocation(prewarp_program, "image_size");
 539 }
 540
 541 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)
 542 {
 543         glUseProgram(prewarp_program);
 544
 545         bind_sampler(prewarp_program, uniform_image0_tex, 0, tex0_view, nearest_sampler);
 546         bind_sampler(prewarp_program, uniform_image1_tex, 1, tex1_view, linear_sampler);
 547         bind_sampler(prewarp_program, uniform_flow_tex, 2, flow_tex, nearest_sampler);
 548
 549         glProgramUniform2f(prewarp_program, uniform_image_size, level_width, level_height);
 550
 551         glViewport(0, 0, level_width, level_height);
 552         glDisable(GL_BLEND);
 553         glBindVertexArray(prewarp_vao);
 554         fbos.render_to(I_tex, I_t_tex, normalized_flow_tex);
 555         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 556 }
 557
 558 // From I, calculate the partial derivatives I_x and I_y. We use a four-tap
 559 // central difference filter, since apparently, that's tradition (I haven't
 560 // measured quality versus a more normal 0.5 (I[x+1] - I[x-1]).)
 561 // The coefficients come from
 562 //
 563 //   https://en.wikipedia.org/wiki/Finite_difference_coefficient
 564 //
 565 // Also computes β_0, since it depends only on I_x and I_y.
 566 class Derivatives {
 567 public:
 568         Derivatives();
 569         void exec(GLuint input_tex, GLuint I_x_y_tex, GLuint beta_0_tex, int level_width, int level_height);
 570
 571 private:
 572         PersistentFBOSet<2> fbos;
 573
 574         GLuint derivatives_vs_obj;
 575         GLuint derivatives_fs_obj;
 576         GLuint derivatives_program;
 577         GLuint derivatives_vao;
 578
 579         GLuint uniform_tex;
 580 };
 581
 582 Derivatives::Derivatives()
 583 {
 584         derivatives_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
 585         derivatives_fs_obj = compile_shader(read_file("derivatives.frag"), GL_FRAGMENT_SHADER);
 586         derivatives_program = link_program(derivatives_vs_obj, derivatives_fs_obj);
 587
 588         // Set up the VAO containing all the required position/texcoord data.
 589         glCreateVertexArrays(1, &derivatives_vao);
 590         glBindVertexArray(derivatives_vao);
 591         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 592
 593         GLint position_attrib = glGetAttribLocation(derivatives_program, "position");
 594         glEnableVertexArrayAttrib(derivatives_vao, position_attrib);
 595         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 596
 597         uniform_tex = glGetUniformLocation(derivatives_program, "tex");
 598 }
 599
 600 void Derivatives::exec(GLuint input_tex, GLuint I_x_y_tex, GLuint beta_0_tex, int level_width, int level_height)
 601 {
 602         glUseProgram(derivatives_program);
 603
 604         bind_sampler(derivatives_program, uniform_tex, 0, input_tex, nearest_sampler);
 605
 606         glViewport(0, 0, level_width, level_height);
 607         glDisable(GL_BLEND);
 608         glBindVertexArray(derivatives_vao);
 609         fbos.render_to(I_x_y_tex, beta_0_tex);
 610         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 611 }
 612
 613 // Calculate the smoothness constraints between neighboring pixels;
 614 // s_x(x,y) stores smoothness between pixel (x,y) and (x+1,y),
 615 // and s_y(x,y) stores between (x,y) and (x,y+1). We'll sample with
 616 // border color (0,0) later, so that there's zero diffusion out of
 617 // the border.
 618 //
 619 // See variational_refinement.txt for more information.
 620 class ComputeSmoothness {
 621 public:
 622         ComputeSmoothness();
 623         void exec(GLuint flow_tex, GLuint diff_flow_tex, GLuint smoothness_x_tex, GLuint smoothness_y_tex, int level_width, int level_height);
 624
 625 private:
 626         PersistentFBOSet<2> fbos;
 627
 628         GLuint smoothness_vs_obj;
 629         GLuint smoothness_fs_obj;
 630         GLuint smoothness_program;
 631         GLuint smoothness_vao;
 632
 633         GLuint uniform_flow_tex, uniform_diff_flow_tex;
 634         GLuint uniform_alpha;
 635 };
 636
 637 ComputeSmoothness::ComputeSmoothness()
 638 {
 639         smoothness_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
 640         smoothness_fs_obj = compile_shader(read_file("smoothness.frag"), GL_FRAGMENT_SHADER);
 641         smoothness_program = link_program(smoothness_vs_obj, smoothness_fs_obj);
 642
 643         // Set up the VAO containing all the required position/texcoord data.
 644         glCreateVertexArrays(1, &smoothness_vao);
 645         glBindVertexArray(smoothness_vao);
 646         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 647
 648         GLint position_attrib = glGetAttribLocation(smoothness_program, "position");
 649         glEnableVertexArrayAttrib(smoothness_vao, position_attrib);
 650         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 651
 652         uniform_flow_tex = glGetUniformLocation(smoothness_program, "flow_tex");
 653         uniform_diff_flow_tex = glGetUniformLocation(smoothness_program, "diff_flow_tex");
 654         uniform_alpha = glGetUniformLocation(smoothness_program, "alpha");
 655 }
 656
 657 void ComputeSmoothness::exec(GLuint flow_tex, GLuint diff_flow_tex, GLuint smoothness_x_tex, GLuint smoothness_y_tex, int level_width, int level_height)
 658 {
 659         glUseProgram(smoothness_program);
 660
 661         bind_sampler(smoothness_program, uniform_flow_tex, 0, flow_tex, nearest_sampler);
 662         bind_sampler(smoothness_program, uniform_diff_flow_tex, 1, diff_flow_tex, nearest_sampler);
 663         glProgramUniform1f(smoothness_program, uniform_alpha, vr_alpha);
 664
 665         glViewport(0, 0, level_width, level_height);
 666
 667         glDisable(GL_BLEND);
 668         glBindVertexArray(smoothness_vao);
 669         fbos.render_to(smoothness_x_tex, smoothness_y_tex);
 670         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 671
 672         // Make sure the smoothness on the right and upper borders is zero.
 673         // We could have done this by making (W-1)xH and Wx(H-1) textures instead
 674         // (we're sampling smoothness with all-zero border color), but we'd
 675         // have to adjust the sampling coordinates, which is annoying.
 676         glClearTexSubImage(smoothness_x_tex, 0,  level_width - 1, 0, 0,   1, level_height, 1,  GL_RED, GL_FLOAT, nullptr);
 677         glClearTexSubImage(smoothness_y_tex, 0,  0, level_height - 1, 0,  level_width, 1, 1,   GL_RED, GL_FLOAT, nullptr);
 678 }
 679
 680 // Set up the equations set (two equations in two unknowns, per pixel).
 681 // We store five floats; the three non-redundant elements of the 2x2 matrix (A)
 682 // as 32-bit floats, and the two elements on the right-hand side (b) as 16-bit
 683 // floats. (Actually, we store the inverse of the diagonal elements, because
 684 // we only ever need to divide by them.) This fits into four u32 values;
 685 // R, G, B for the matrix (the last element is symmetric) and A for the two b values.
 686 // All the values of the energy term (E_I, E_G, E_S), except the smoothness
 687 // terms that depend on other pixels, are calculated in one pass.
 688 //
 689 // See variational_refinement.txt for more information.
 690 class SetupEquations {
 691 public:
 692         SetupEquations();
 693         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);
 694
 695 private:
 696         PersistentFBOSet<1> fbos;
 697
 698         GLuint equations_vs_obj;
 699         GLuint equations_fs_obj;
 700         GLuint equations_program;
 701         GLuint equations_vao;
 702
 703         GLuint uniform_I_x_y_tex, uniform_I_t_tex;
 704         GLuint uniform_diff_flow_tex, uniform_base_flow_tex;
 705         GLuint uniform_beta_0_tex;
 706         GLuint uniform_smoothness_x_tex, uniform_smoothness_y_tex;
 707         GLuint uniform_gamma, uniform_delta;
 708 };
 709
 710 SetupEquations::SetupEquations()
 711 {
 712         equations_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
 713         equations_fs_obj = compile_shader(read_file("equations.frag"), GL_FRAGMENT_SHADER);
 714         equations_program = link_program(equations_vs_obj, equations_fs_obj);
 715
 716         // Set up the VAO containing all the required position/texcoord data.
 717         glCreateVertexArrays(1, &equations_vao);
 718         glBindVertexArray(equations_vao);
 719         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 720
 721         GLint position_attrib = glGetAttribLocation(equations_program, "position");
 722         glEnableVertexArrayAttrib(equations_vao, position_attrib);
 723         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 724
 725         uniform_I_x_y_tex = glGetUniformLocation(equations_program, "I_x_y_tex");
 726         uniform_I_t_tex = glGetUniformLocation(equations_program, "I_t_tex");
 727         uniform_diff_flow_tex = glGetUniformLocation(equations_program, "diff_flow_tex");
 728         uniform_base_flow_tex = glGetUniformLocation(equations_program, "base_flow_tex");
 729         uniform_beta_0_tex = glGetUniformLocation(equations_program, "beta_0_tex");
 730         uniform_smoothness_x_tex = glGetUniformLocation(equations_program, "smoothness_x_tex");
 731         uniform_smoothness_y_tex = glGetUniformLocation(equations_program, "smoothness_y_tex");
 732         uniform_gamma = glGetUniformLocation(equations_program, "gamma");
 733         uniform_delta = glGetUniformLocation(equations_program, "delta");
 734 }
 735
 736 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)
 737 {
 738         glUseProgram(equations_program);
 739
 740         bind_sampler(equations_program, uniform_I_x_y_tex, 0, I_x_y_tex, nearest_sampler);
 741         bind_sampler(equations_program, uniform_I_t_tex, 1, I_t_tex, nearest_sampler);
 742         bind_sampler(equations_program, uniform_diff_flow_tex, 2, diff_flow_tex, nearest_sampler);
 743         bind_sampler(equations_program, uniform_base_flow_tex, 3, base_flow_tex, nearest_sampler);
 744         bind_sampler(equations_program, uniform_beta_0_tex, 4, beta_0_tex, nearest_sampler);
 745         bind_sampler(equations_program, uniform_smoothness_x_tex, 5, smoothness_x_tex, smoothness_sampler);
 746         bind_sampler(equations_program, uniform_smoothness_y_tex, 6, smoothness_y_tex, smoothness_sampler);
 747         glProgramUniform1f(equations_program, uniform_delta, vr_delta);
 748         glProgramUniform1f(equations_program, uniform_gamma, vr_gamma);
 749
 750         glViewport(0, 0, level_width, level_height);
 751         glDisable(GL_BLEND);
 752         glBindVertexArray(equations_vao);
 753         fbos.render_to(equation_tex);
 754         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 755 }
 756
 757 // Actually solve the equation sets made by SetupEquations, by means of
 758 // successive over-relaxation (SOR).
 759 //
 760 // See variational_refinement.txt for more information.
 761 class SOR {
 762 public:
 763         SOR();
 764         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);
 765
 766 private:
 767         PersistentFBOSet<1> fbos;
 768
 769         GLuint sor_vs_obj;
 770         GLuint sor_fs_obj;
 771         GLuint sor_program;
 772         GLuint sor_vao;
 773
 774         GLuint uniform_diff_flow_tex;
 775         GLuint uniform_equation_tex;
 776         GLuint uniform_smoothness_x_tex, uniform_smoothness_y_tex;
 777 };
 778
 779 SOR::SOR()
 780 {
 781         sor_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
 782         sor_fs_obj = compile_shader(read_file("sor.frag"), GL_FRAGMENT_SHADER);
 783         sor_program = link_program(sor_vs_obj, sor_fs_obj);
 784
 785         // Set up the VAO containing all the required position/texcoord data.
 786         glCreateVertexArrays(1, &sor_vao);
 787         glBindVertexArray(sor_vao);
 788         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 789
 790         GLint position_attrib = glGetAttribLocation(sor_program, "position");
 791         glEnableVertexArrayAttrib(sor_vao, position_attrib);
 792         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 793
 794         uniform_diff_flow_tex = glGetUniformLocation(sor_program, "diff_flow_tex");
 795         uniform_equation_tex = glGetUniformLocation(sor_program, "equation_tex");
 796         uniform_smoothness_x_tex = glGetUniformLocation(sor_program, "smoothness_x_tex");
 797         uniform_smoothness_y_tex = glGetUniformLocation(sor_program, "smoothness_y_tex");
 798 }
 799
 800 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)
 801 {
 802         glUseProgram(sor_program);
 803
 804         bind_sampler(sor_program, uniform_diff_flow_tex, 0, diff_flow_tex, nearest_sampler);
 805         bind_sampler(sor_program, uniform_smoothness_x_tex, 1, smoothness_x_tex, smoothness_sampler);
 806         bind_sampler(sor_program, uniform_smoothness_y_tex, 2, smoothness_y_tex, smoothness_sampler);
 807         bind_sampler(sor_program, uniform_equation_tex, 3, equation_tex, nearest_sampler);
 808
 809         glViewport(0, 0, level_width, level_height);
 810         glDisable(GL_BLEND);
 811         glBindVertexArray(sor_vao);
 812         fbos.render_to(diff_flow_tex);  // NOTE: Bind to same as we render from!
 813
 814         for (int i = 0; i < num_iterations; ++i) {
 815                 glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 816                 if (i != num_iterations - 1) {
 817                         glTextureBarrier();
 818                 }
 819         }
 820 }
 821
 822 // Simply add the differential flow found by the variational refinement to the base flow.
 823 // The output is in base_flow_tex; we don't need to make a new texture.
 824 class AddBaseFlow {
 825 public:
 826         AddBaseFlow();
 827         void exec(GLuint base_flow_tex, GLuint diff_flow_tex, int level_width, int level_height);
 828
 829 private:
 830         PersistentFBOSet<1> fbos;
 831
 832         GLuint add_flow_vs_obj;
 833         GLuint add_flow_fs_obj;
 834         GLuint add_flow_program;
 835         GLuint add_flow_vao;
 836
 837         GLuint uniform_diff_flow_tex;
 838 };
 839
 840 AddBaseFlow::AddBaseFlow()
 841 {
 842         add_flow_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
 843         add_flow_fs_obj = compile_shader(read_file("add_base_flow.frag"), GL_FRAGMENT_SHADER);
 844         add_flow_program = link_program(add_flow_vs_obj, add_flow_fs_obj);
 845
 846         // Set up the VAO containing all the required position/texcoord data.
 847         glCreateVertexArrays(1, &add_flow_vao);
 848         glBindVertexArray(add_flow_vao);
 849         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 850
 851         GLint position_attrib = glGetAttribLocation(add_flow_program, "position");
 852         glEnableVertexArrayAttrib(add_flow_vao, position_attrib);
 853         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 854
 855         uniform_diff_flow_tex = glGetUniformLocation(add_flow_program, "diff_flow_tex");
 856 }
 857
 858 void AddBaseFlow::exec(GLuint base_flow_tex, GLuint diff_flow_tex, int level_width, int level_height)
 859 {
 860         glUseProgram(add_flow_program);
 861
 862         bind_sampler(add_flow_program, uniform_diff_flow_tex, 0, diff_flow_tex, nearest_sampler);
 863
 864         glViewport(0, 0, level_width, level_height);
 865         glEnable(GL_BLEND);
 866         glBlendFunc(GL_ONE, GL_ONE);
 867         glBindVertexArray(add_flow_vao);
 868         fbos.render_to(base_flow_tex);
 869
 870         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 871 }
 872
 873 // Take a copy of the flow, bilinearly interpolated and scaled up.
 874 class ResizeFlow {
 875 public:
 876         ResizeFlow();
 877         void exec(GLuint in_tex, GLuint out_tex, int input_width, int input_height, int output_width, int output_height);
 878
 879 private:
 880         PersistentFBOSet<1> fbos;
 881
 882         GLuint resize_flow_vs_obj;
 883         GLuint resize_flow_fs_obj;
 884         GLuint resize_flow_program;
 885         GLuint resize_flow_vao;
 886
 887         GLuint uniform_flow_tex;
 888         GLuint uniform_scale_factor;
 889 };
 890
 891 ResizeFlow::ResizeFlow()
 892 {
 893         resize_flow_vs_obj = compile_shader(read_file("vs.vert"), GL_VERTEX_SHADER);
 894         resize_flow_fs_obj = compile_shader(read_file("resize_flow.frag"), GL_FRAGMENT_SHADER);
 895         resize_flow_program = link_program(resize_flow_vs_obj, resize_flow_fs_obj);
 896
 897         // Set up the VAO containing all the required position/texcoord data.
 898         glCreateVertexArrays(1, &resize_flow_vao);
 899         glBindVertexArray(resize_flow_vao);
 900         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
 901
 902         GLint position_attrib = glGetAttribLocation(resize_flow_program, "position");
 903         glEnableVertexArrayAttrib(resize_flow_vao, position_attrib);
 904         glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 905
 906         uniform_flow_tex = glGetUniformLocation(resize_flow_program, "flow_tex");
 907         uniform_scale_factor = glGetUniformLocation(resize_flow_program, "scale_factor");
 908 }
 909
 910 void ResizeFlow::exec(GLuint flow_tex, GLuint out_tex, int input_width, int input_height, int output_width, int output_height)
 911 {
 912         glUseProgram(resize_flow_program);
 913
 914         bind_sampler(resize_flow_program, uniform_flow_tex, 0, flow_tex, nearest_sampler);
 915
 916         glProgramUniform2f(resize_flow_program, uniform_scale_factor, float(output_width) / input_width, float(output_height) / input_height);
 917
 918         glViewport(0, 0, output_width, output_height);
 919         glDisable(GL_BLEND);
 920         glBindVertexArray(resize_flow_vao);
 921         fbos.render_to(out_tex);
 922
 923         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 924 }
 925
 926 class GPUTimers {
 927 public:
 928         void print();
 929         pair<GLuint, GLuint> begin_timer(const string &name, int level);
 930
 931 private:
 932         struct Timer {
 933                 string name;
 934                 int level;
 935                 pair<GLuint, GLuint> query;
 936         };
 937         vector<Timer> timers;
 938 };
 939
 940 pair<GLuint, GLuint> GPUTimers::begin_timer(const string &name, int level)
 941 {
 942         if (!enable_timing) {
 943                 return make_pair(0, 0);
 944         }
 945
 946         GLuint queries[2];
 947         glGenQueries(2, queries);
 948         glQueryCounter(queries[0], GL_TIMESTAMP);
 949
 950         Timer timer;
 951         timer.name = name;
 952         timer.level = level;
 953         timer.query.first = queries[0];
 954         timer.query.second = queries[1];
 955         timers.push_back(timer);
 956         return timer.query;
 957 }
 958
 959 void GPUTimers::print()
 960 {
 961         for (const Timer &timer : timers) {
 962                 // NOTE: This makes the CPU wait for the GPU.
 963                 GLuint64 time_start, time_end;
 964                 glGetQueryObjectui64v(timer.query.first, GL_QUERY_RESULT, &time_start);
 965                 glGetQueryObjectui64v(timer.query.second, GL_QUERY_RESULT, &time_end);
 966                 //fprintf(stderr, "GPU time used = %.1f ms\n", time_elapsed / 1e6);
 967                 for (int i = 0; i < timer.level * 2; ++i) {
 968                         fprintf(stderr, " ");
 969                 }
 970                 fprintf(stderr, "%-30s %4.1f ms\n", timer.name.c_str(), GLint64(time_end - time_start) / 1e6);
 971         }
 972 }
 973
 974 // A simple RAII class for timing until the end of the scope.
 975 class ScopedTimer {
 976 public:
 977         ScopedTimer(const string &name, GPUTimers *timers)
 978                 : timers(timers), level(0)
 979         {
 980                 query = timers->begin_timer(name, level);
 981         }
 982
 983         ScopedTimer(const string &name, ScopedTimer *parent_timer)
 984                 : timers(parent_timer->timers),
 985                   level(parent_timer->level + 1)
 986         {
 987                 query = timers->begin_timer(name, level);
 988         }
 989
 990         ~ScopedTimer()
 991         {
 992                 end();
 993         }
 994
 995         void end()
 996         {
 997                 if (enable_timing && !ended) {
 998                         glQueryCounter(query.second, GL_TIMESTAMP);
 999                         ended = true;
1000                 }
1001         }
1002
1003 private:
1004         GPUTimers *timers;
1005         int level;
1006         pair<GLuint, GLuint> query;
1007         bool ended = false;
1008 };
1009
1010 class DISComputeFlow {
1011 public:
1012         DISComputeFlow(int width, int height);
1013
1014         // Returns a texture that must be released with release_texture()
1015         // after use.
1016         GLuint exec(GLuint tex0, GLuint tex1);
1017         void release_texture(GLuint tex);
1018
1019 private:
1020         int width, height;
1021         GLuint initial_flow_tex;
1022
1023         // The various passes.
1024         Sobel sobel;
1025         MotionSearch motion_search;
1026         Densify densify;
1027         Prewarp prewarp;
1028         Derivatives derivatives;
1029         ComputeSmoothness compute_smoothness;
1030         SetupEquations setup_equations;
1031         SOR sor;
1032         AddBaseFlow add_base_flow;
1033         ResizeFlow resize_flow;
1034
1035         struct Texture {
1036                 GLuint tex_num;
1037                 GLenum format;
1038                 GLuint width, height;
1039                 bool in_use = false;
1040         };
1041         vector<Texture> textures;
1042
1043         GLuint get_texture(GLenum format, GLuint width, GLuint height);
1044 };
1045
1046 DISComputeFlow::DISComputeFlow(int width, int height)
1047         : width(width), height(height)
1048 {
1049         // Make some samplers.
1050         glCreateSamplers(1, &nearest_sampler);
1051         glSamplerParameteri(nearest_sampler, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
1052         glSamplerParameteri(nearest_sampler, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
1053         glSamplerParameteri(nearest_sampler, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
1054         glSamplerParameteri(nearest_sampler, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
1055
1056         glCreateSamplers(1, &linear_sampler);
1057         glSamplerParameteri(linear_sampler, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
1058         glSamplerParameteri(linear_sampler, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
1059         glSamplerParameteri(linear_sampler, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
1060         glSamplerParameteri(linear_sampler, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
1061
1062         // The smoothness is sampled so that once we get to a smoothness involving
1063         // a value outside the border, the diffusivity between the two becomes zero.
1064         glCreateSamplers(1, &smoothness_sampler);
1065         glSamplerParameteri(smoothness_sampler, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
1066         glSamplerParameteri(smoothness_sampler, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
1067         glSamplerParameteri(smoothness_sampler, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
1068         glSamplerParameteri(smoothness_sampler, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
1069         float zero[] = { 0.0f, 0.0f, 0.0f, 0.0f };
1070         glSamplerParameterfv(smoothness_sampler, GL_TEXTURE_BORDER_COLOR, zero);
1071
1072         // Initial flow is zero, 1x1.
1073         glCreateTextures(GL_TEXTURE_2D, 1, &initial_flow_tex);
1074         glTextureStorage2D(initial_flow_tex, 1, GL_RG16F, 1, 1);
1075         glClearTexImage(initial_flow_tex, 0, GL_RG, GL_FLOAT, nullptr);
1076 }
1077
1078 GLuint DISComputeFlow::exec(GLuint tex0, GLuint tex1)
1079 {
1080         for (const Texture &tex : textures) {
1081                 assert(!tex.in_use);
1082         }
1083
1084         int prev_level_width = 1, prev_level_height = 1;
1085         GLuint prev_level_flow_tex = initial_flow_tex;
1086
1087         GPUTimers timers;
1088
1089         ScopedTimer total_timer("Total", &timers);
1090         for (int level = coarsest_level; level >= int(finest_level); --level) {
1091                 char timer_name[256];
1092                 snprintf(timer_name, sizeof(timer_name), "Level %d", level);
1093                 ScopedTimer level_timer(timer_name, &total_timer);
1094
1095                 int level_width = width >> level;
1096                 int level_height = height >> level;
1097                 float patch_spacing_pixels = patch_size_pixels * (1.0f - patch_overlap_ratio);
1098                 int width_patches = 1 + lrintf((level_width - patch_size_pixels) / patch_spacing_pixels);
1099                 int height_patches = 1 + lrintf((level_height - patch_size_pixels) / patch_spacing_pixels);
1100
1101                 // Make sure we always read from the correct level; the chosen
1102                 // mipmapping could otherwise be rather unpredictable, especially
1103                 // during motion search.
1104                 // TODO: create these beforehand, and stop leaking them.
1105                 GLuint tex0_view, tex1_view;
1106                 glGenTextures(1, &tex0_view);
1107                 glTextureView(tex0_view, GL_TEXTURE_2D, tex0, GL_R8, level, 1, 0, 1);
1108                 glGenTextures(1, &tex1_view);
1109                 glTextureView(tex1_view, GL_TEXTURE_2D, tex1, GL_R8, level, 1, 0, 1);
1110
1111                 // Create a new texture; we could be fancy and render use a multi-level
1112                 // texture, but meh.
1113                 GLuint grad0_tex = get_texture(GL_RG16F, level_width, level_height);
1114
1115                 // Find the derivative.
1116                 {
1117                         ScopedTimer timer("Sobel", &level_timer);
1118                         sobel.exec(tex0_view, grad0_tex, level_width, level_height);
1119                 }
1120
1121                 // Motion search to find the initial flow. We use the flow from the previous
1122                 // level (sampled bilinearly; no fancy tricks) as a guide, then search from there.
1123
1124                 // Create an output flow texture.
1125                 GLuint flow_out_tex = get_texture(GL_RGB16F, width_patches, height_patches);
1126
1127                 // And draw.
1128                 {
1129                         ScopedTimer timer("Motion search", &level_timer);
1130                         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);
1131                 }
1132                 release_texture(grad0_tex);
1133
1134                 // Densification.
1135
1136                 // Set up an output texture (initially zero).
1137                 GLuint dense_flow_tex = get_texture(GL_RGB16F, level_width, level_height);
1138                 glClearTexImage(dense_flow_tex, 0, GL_RGB, GL_FLOAT, nullptr);
1139
1140                 // And draw.
1141                 {
1142                         ScopedTimer timer("Densification", &level_timer);
1143                         densify.exec(tex0_view, tex1_view, flow_out_tex, dense_flow_tex, level_width, level_height, width_patches, height_patches);
1144                 }
1145                 release_texture(flow_out_tex);
1146
1147                 // Everything below here in the loop belongs to variational refinement.
1148                 ScopedTimer varref_timer("Variational refinement", &level_timer);
1149
1150                 // Prewarping; create I and I_t, and a normalized base flow (so we don't
1151                 // have to normalize it over and over again, and also save some bandwidth).
1152                 //
1153                 // During the entire rest of the variational refinement, flow will be measured
1154                 // in pixels, not 0..1 normalized OpenGL texture coordinates.
1155                 // This is because variational refinement depends so heavily on derivatives,
1156                 // which are measured in intensity levels per pixel.
1157                 GLuint I_tex = get_texture(GL_R16F, level_width, level_height);
1158                 GLuint I_t_tex = get_texture(GL_R16F, level_width, level_height);
1159                 GLuint base_flow_tex = get_texture(GL_RG16F, level_width, level_height);
1160                 {
1161                         ScopedTimer timer("Prewarping", &varref_timer);
1162                         prewarp.exec(tex0_view, tex1_view, dense_flow_tex, I_tex, I_t_tex, base_flow_tex, level_width, level_height);
1163                 }
1164                 release_texture(dense_flow_tex);
1165
1166                 // Calculate I_x and I_y. We're only calculating first derivatives;
1167                 // the others will be taken on-the-fly in order to sample from fewer
1168                 // textures overall, since sampling from the L1 cache is cheap.
1169                 // (TODO: Verify that this is indeed faster than making separate
1170                 // double-derivative textures.)
1171                 GLuint I_x_y_tex = get_texture(GL_RG16F, level_width, level_height);
1172                 GLuint beta_0_tex = get_texture(GL_R16F, level_width, level_height);
1173                 {
1174                         ScopedTimer timer("First derivatives", &varref_timer);
1175                         derivatives.exec(I_tex, I_x_y_tex, beta_0_tex, level_width, level_height);
1176                 }
1177                 release_texture(I_tex);
1178
1179                 // We need somewhere to store du and dv (the flow increment, relative
1180                 // to the non-refined base flow u0 and v0). It starts at zero.
1181                 GLuint du_dv_tex = get_texture(GL_RG16F, level_width, level_height);
1182                 glClearTexImage(du_dv_tex, 0, GL_RG, GL_FLOAT, nullptr);
1183
1184                 // And for smoothness.
1185                 GLuint smoothness_x_tex = get_texture(GL_R16F, level_width, level_height);
1186                 GLuint smoothness_y_tex = get_texture(GL_R16F, level_width, level_height);
1187
1188                 // And finally for the equation set. See SetupEquations for
1189                 // the storage format.
1190                 GLuint equation_tex = get_texture(GL_RGBA32UI, level_width, level_height);
1191
1192                 for (int outer_idx = 0; outer_idx < level + 1; ++outer_idx) {
1193                         // Calculate the smoothness terms between the neighboring pixels,
1194                         // both in x and y direction.
1195                         {
1196                                 ScopedTimer timer("Compute smoothness", &varref_timer);
1197                                 compute_smoothness.exec(base_flow_tex, du_dv_tex, smoothness_x_tex, smoothness_y_tex, level_width, level_height);
1198                         }
1199
1200                         // Set up the 2x2 equation system for each pixel.
1201                         {
1202                                 ScopedTimer timer("Set up equations", &varref_timer);
1203                                 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);
1204                         }
1205
1206                         // Run a few SOR (or quasi-SOR, since we're not really Jacobi) iterations.
1207                         // Note that these are to/from the same texture.
1208                         {
1209                                 ScopedTimer timer("SOR", &varref_timer);
1210                                 sor.exec(du_dv_tex, equation_tex, smoothness_x_tex, smoothness_y_tex, level_width, level_height, 5);
1211                         }
1212                 }
1213
1214                 release_texture(I_t_tex);
1215                 release_texture(I_x_y_tex);
1216                 release_texture(beta_0_tex);
1217                 release_texture(smoothness_x_tex);
1218                 release_texture(smoothness_y_tex);
1219                 release_texture(equation_tex);
1220
1221                 // Add the differential flow found by the variational refinement to the base flow,
1222                 // giving the final flow estimate for this level.
1223                 // The output is in diff_flow_tex; we don't need to make a new texture.
1224                 //
1225                 // Disabling this doesn't save any time (although we could easily make it so that
1226                 // it is more efficient), but it helps debug the motion search.
1227                 if (enable_variational_refinement) {
1228                         ScopedTimer timer("Add differential flow", &varref_timer);
1229                         add_base_flow.exec(base_flow_tex, du_dv_tex, level_width, level_height);
1230                 }
1231                 release_texture(du_dv_tex);
1232
1233                 if (prev_level_flow_tex != initial_flow_tex) {
1234                         release_texture(prev_level_flow_tex);
1235                 }
1236                 prev_level_flow_tex = base_flow_tex;
1237                 prev_level_width = level_width;
1238                 prev_level_height = level_height;
1239         }
1240         total_timer.end();
1241
1242         timers.print();
1243
1244         // Scale up the flow to the final size (if needed).
1245         if (finest_level == 0) {
1246                 return prev_level_flow_tex;
1247         } else {
1248                 GLuint final_tex = get_texture(GL_RG16F, width, height);
1249                 resize_flow.exec(prev_level_flow_tex, final_tex, prev_level_width, prev_level_height, width, height);
1250                 release_texture(prev_level_flow_tex);
1251                 return final_tex;
1252         }
1253 }
1254
1255 GLuint DISComputeFlow::get_texture(GLenum format, GLuint width, GLuint height)
1256 {
1257         for (Texture &tex : textures) {
1258                 if (!tex.in_use && tex.format == format &&
1259                     tex.width == width && tex.height == height) {
1260                         tex.in_use = true;
1261                         return tex.tex_num;
1262                 }
1263         }
1264
1265         Texture tex;
1266         glCreateTextures(GL_TEXTURE_2D, 1, &tex.tex_num);
1267         glTextureStorage2D(tex.tex_num, 1, format, width, height);
1268         tex.format = format;
1269         tex.width = width;
1270         tex.height = height;
1271         tex.in_use = true;
1272         textures.push_back(tex);
1273         return tex.tex_num;
1274 }
1275
1276 void DISComputeFlow::release_texture(GLuint tex_num)
1277 {
1278         for (Texture &tex : textures) {
1279                 if (tex.tex_num == tex_num) {
1280                         assert(tex.in_use);
1281                         tex.in_use = false;
1282                         return;
1283                 }
1284         }
1285         assert(false);
1286 }
1287
1288 // OpenGL uses a bottom-left coordinate system, .flo files use a top-left coordinate system.
1289 void flip_coordinate_system(float *dense_flow, unsigned width, unsigned height)
1290 {
1291         for (unsigned i = 0; i < width * height; ++i) {
1292                 dense_flow[i * 2 + 1] = -dense_flow[i * 2 + 1];
1293         }
1294 }
1295
1296 void write_flow(const char *filename, const float *dense_flow, unsigned width, unsigned height)
1297 {
1298         FILE *flowfp = fopen(filename, "wb");
1299         fprintf(flowfp, "FEIH");
1300         fwrite(&width, 4, 1, flowfp);
1301         fwrite(&height, 4, 1, flowfp);
1302         for (unsigned y = 0; y < height; ++y) {
1303                 int yy = height - y - 1;
1304                 fwrite(&dense_flow[yy * width * 2], width * 2 * sizeof(float), 1, flowfp);
1305         }
1306         fclose(flowfp);
1307 }
1308
1309 void write_ppm(const char *filename, const float *dense_flow, unsigned width, unsigned height)
1310 {
1311         FILE *fp = fopen(filename, "wb");
1312         fprintf(fp, "P6\n%d %d\n255\n", width, height);
1313         for (unsigned y = 0; y < unsigned(height); ++y) {
1314                 int yy = height - y - 1;
1315                 for (unsigned x = 0; x < unsigned(width); ++x) {
1316                         float du = dense_flow[(yy * width + x) * 2 + 0];
1317                         float dv = dense_flow[(yy * width + x) * 2 + 1];
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 }
1328
1329 void finish_one_read(GLuint width, GLuint height)
1330 {
1331         assert(!reads_in_progress.empty());
1332         ReadInProgress read = reads_in_progress.front();
1333         reads_in_progress.pop_front();
1334
1335         unique_ptr<float[]> flow(new float[width * height * 2]);
1336         void *buf = glMapNamedBufferRange(read.pbo, 0, width * height * 2 * sizeof(float), GL_MAP_READ_BIT);  // Blocks if the read isn't done yet.
1337         memcpy(flow.get(), buf, width * height * 2 * sizeof(float));
1338         glUnmapNamedBuffer(read.pbo);
1339         spare_pbos.push(read.pbo);
1340
1341         flip_coordinate_system(flow.get(), width, height);
1342         if (!read.flow_filename.empty()) {
1343                 write_flow(read.flow_filename.c_str(), flow.get(), width, height);
1344                 fprintf(stderr, "%s %s -> %s\n", read.filename0.c_str(), read.filename1.c_str(), read.flow_filename.c_str());
1345         }
1346         if (!read.ppm_filename.empty()) {
1347                 write_ppm(read.ppm_filename.c_str(), flow.get(), width, height);
1348         }
1349 }
1350
1351 void schedule_read(GLuint tex, GLuint width, GLuint height, const char *filename0, const char *filename1, const char *flow_filename, const char *ppm_filename)
1352 {
1353         if (spare_pbos.empty()) {
1354                 finish_one_read(width, height);
1355         }
1356         assert(!spare_pbos.empty());
1357         reads_in_progress.emplace_back(ReadInProgress{ spare_pbos.top(), filename0, filename1, flow_filename, ppm_filename });
1358         glBindBuffer(GL_PIXEL_PACK_BUFFER, spare_pbos.top());
1359         spare_pbos.pop();
1360         glGetTextureImage(tex, 0, GL_RG, GL_FLOAT, width * height * 2 * sizeof(float), nullptr);
1361         glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);
1362 }
1363
1364 int main(int argc, char **argv)
1365 {
1366         static const option long_options[] = {
1367                 { "alpha", required_argument, 0, 'a' },
1368                 { "delta", required_argument, 0, 'd' },
1369                 { "gamma", required_argument, 0, 'g' },
1370                 { "disable-timing", no_argument, 0, 1000 },
1371                 { "ignore-variational-refinement", no_argument, 0, 1001 }  // Still calculates it, just doesn't apply it.
1372         };
1373
1374         for ( ;; ) {
1375                 int option_index = 0;
1376                 int c = getopt_long(argc, argv, "a:d:g:", long_options, &option_index);
1377
1378                 if (c == -1) {
1379                         break;
1380                 }
1381                 switch (c) {
1382                 case 'a':
1383                         vr_alpha = atof(optarg);
1384                         break;
1385                 case 'd':
1386                         vr_delta = atof(optarg);
1387                         break;
1388                 case 'g':
1389                         vr_gamma = atof(optarg);
1390                         break;
1391                 case 1000:
1392                         enable_timing = false;
1393                         break;
1394                 case 1001:
1395                         enable_variational_refinement = false;
1396                         break;
1397                 default:
1398                         fprintf(stderr, "Unknown option '%s'\n", argv[option_index]);
1399                         exit(1);
1400                 };
1401         }
1402
1403         if (SDL_Init(SDL_INIT_EVERYTHING) == -1) {
1404                 fprintf(stderr, "SDL_Init failed: %s\n", SDL_GetError());
1405                 exit(1);
1406         }
1407         SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);
1408         SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 0);
1409         SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 0);
1410         SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
1411
1412         SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
1413         SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4);
1414         SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 5);
1415         // SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_DEBUG_FLAG);
1416         SDL_Window *window = SDL_CreateWindow("OpenGL window",
1417                         SDL_WINDOWPOS_UNDEFINED,
1418                         SDL_WINDOWPOS_UNDEFINED,
1419                         64, 64,
1420                         SDL_WINDOW_OPENGL);
1421         SDL_GLContext context = SDL_GL_CreateContext(window);
1422         assert(context != nullptr);
1423
1424         const char *filename0 = argc >= (optind + 1) ? argv[optind] : "test1499.png";
1425         const char *filename1 = argc >= (optind + 2) ? argv[optind + 1] : "test1500.png";
1426         const char *flow_filename = argc >= (optind + 3) ? argv[optind + 2] : "flow.flo";
1427
1428         // Load pictures.
1429         unsigned width1, height1, width2, height2;
1430         GLuint tex0 = load_texture(filename0, &width1, &height1);
1431         GLuint tex1 = load_texture(filename1, &width2, &height2);
1432
1433         if (width1 != width2 || height1 != height2) {
1434                 fprintf(stderr, "Image dimensions don't match (%dx%d versus %dx%d)\n",
1435                         width1, height1, width2, height2);
1436                 exit(1);
1437         }
1438
1439         // Set up some PBOs to do asynchronous readback.
1440         GLuint pbos[5];
1441         glCreateBuffers(5, pbos);
1442         for (int i = 0; i < 5; ++i) {
1443                 glNamedBufferData(pbos[i], width1 * height1 * 2 * sizeof(float), nullptr, GL_STREAM_READ);
1444                 spare_pbos.push(pbos[i]);
1445         }
1446
1447         // FIXME: Should be part of DISComputeFlow (but needs to be initialized
1448         // before all the render passes).
1449         float vertices[] = {
1450                 0.0f, 1.0f,
1451                 0.0f, 0.0f,
1452                 1.0f, 1.0f,
1453                 1.0f, 0.0f,
1454         };
1455         glCreateBuffers(1, &vertex_vbo);
1456         glNamedBufferData(vertex_vbo, sizeof(vertices), vertices, GL_STATIC_DRAW);
1457         glBindBuffer(GL_ARRAY_BUFFER, vertex_vbo);
1458
1459         DISComputeFlow compute_flow(width1, height1);
1460         GLuint final_tex = compute_flow.exec(tex0, tex1);
1461
1462         schedule_read(final_tex, width1, height1, filename0, filename1, flow_filename, "flow.ppm");
1463         compute_flow.release_texture(final_tex);
1464
1465         // See if there are more flows on the command line (ie., more than three arguments),
1466         // and if so, process them.
1467         int num_flows = (argc - optind) / 3;
1468         for (int i = 1; i < num_flows; ++i) {
1469                 const char *filename0 = argv[optind + i * 3 + 0];
1470                 const char *filename1 = argv[optind + i * 3 + 1];
1471                 const char *flow_filename = argv[optind + i * 3 + 2];
1472                 GLuint width, height;
1473                 GLuint tex0 = load_texture(filename0, &width, &height);
1474                 if (width != width1 || height != height1) {
1475                         fprintf(stderr, "%s: Image dimensions don't match (%dx%d versus %dx%d)\n",
1476                                 filename0, width, height, width1, height1);
1477                         exit(1);
1478                 }
1479
1480                 GLuint tex1 = load_texture(filename1, &width, &height);
1481                 if (width != width1 || height != height1) {
1482                         fprintf(stderr, "%s: Image dimensions don't match (%dx%d versus %dx%d)\n",
1483                                 filename1, width, height, width1, height1);
1484                         exit(1);
1485                 }
1486
1487                 GLuint final_tex = compute_flow.exec(tex0, tex1);
1488                 schedule_read(final_tex, width1, height1, filename0, filename1, flow_filename, "");
1489                 compute_flow.release_texture(final_tex);
1490         }
1491
1492         while (!reads_in_progress.empty()) {
1493                 finish_one_read(width1, height1);
1494         }
1495 }