summaryrefslogtreecommitdiffstats
path: root/libdimension/raytrace.c
blob: 4056f071b1ad6b955bd5dbb8a7133a443b5a470c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
/*************************************************************************
 * Copyright (C) 2010-2011 Tavian Barnes <tavianator@tavianator.com>     *
 *                                                                       *
 * This file is part of The Dimension Library.                           *
 *                                                                       *
 * The Dimension Library is free software; you can redistribute it and/  *
 * or modify it under the terms of the GNU Lesser General Public License *
 * as published by the Free Software Foundation; either version 3 of the *
 * License, or (at your option) any later version.                       *
 *                                                                       *
 * The Dimension Library is distributed in the hope that it will be      *
 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty   *
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU  *
 * Lesser General Public License for more details.                       *
 *                                                                       *
 * You should have received a copy of the GNU Lesser General Public      *
 * License along with this program.  If not, see                         *
 * <http://www.gnu.org/licenses/>.                                       *
 *************************************************************************/

/**
 * @file
 * The ray-tracing algorithm.
 */

#include "dimension-internal.h"
#include <stdlib.h>

/*
 * Boilerplate for multithreading
 */

/** Payload type for passing arguments to worker threads. */
typedef struct {
  dmnsn_future *future;
  dmnsn_scene *scene;
  dmnsn_prtree *prtree;
} dmnsn_ray_trace_payload;

/* Ray-trace a scene */
void
dmnsn_ray_trace(dmnsn_scene *scene)
{
  dmnsn_future *future = dmnsn_ray_trace_async(scene);
  if (dmnsn_future_join(future) != 0) {
    dmnsn_error("Error occured while ray-tracing.");
  }
}

/** Background thread callback. */
static int dmnsn_ray_trace_scene_thread(void *ptr);

/* Ray-trace a scene in the background */
dmnsn_future *
dmnsn_ray_trace_async(dmnsn_scene *scene)
{
  dmnsn_future *future = dmnsn_new_future();

  dmnsn_ray_trace_payload *payload =
    dmnsn_malloc(sizeof(dmnsn_ray_trace_payload));
  payload->future = future;
  payload->scene  = scene;

  dmnsn_new_thread(future, dmnsn_ray_trace_scene_thread, payload);

  return future;
}

/** Worker thread callback. */
static int dmnsn_ray_trace_scene_concurrent(void *ptr, unsigned int thread,
                                            unsigned int nthreads);

/* Thread callback -- set up the multithreaded engine */
static int
dmnsn_ray_trace_scene_thread(void *ptr)
{
  dmnsn_ray_trace_payload *payload = ptr;

  /* Pre-calculate bounding box transformations, etc. */
  dmnsn_scene_initialize(payload->scene);

  /* Time the bounding tree construction */
  dmnsn_timer_start(&payload->scene->bounding_timer);
    payload->prtree = dmnsn_new_prtree(payload->scene->objects);
  dmnsn_timer_stop(&payload->scene->bounding_timer);

  /* Set up the future object */
  dmnsn_future_set_total(payload->future, payload->scene->canvas->height);

  /* Time the render itself */
  dmnsn_timer_start(&payload->scene->render_timer);
    int ret = dmnsn_execute_concurrently(dmnsn_ray_trace_scene_concurrent,
                                         payload, payload->scene->nthreads);
  dmnsn_timer_stop(&payload->scene->render_timer);

  dmnsn_delete_prtree(payload->prtree);
  dmnsn_free(payload);

  return ret;
}

/*
 * Ray-tracing algorithm
 */

/** The current state of the ray-tracing engine. */
typedef struct dmnsn_rtstate {
  const struct dmnsn_rtstate *parent;

  const dmnsn_scene *scene;
  const dmnsn_intersection *intersection;
  const dmnsn_texture *texture;
  const dmnsn_interior *interior;
  const dmnsn_prtree *prtree;
  unsigned int reclevel;

  dmnsn_vector r;
  dmnsn_vector pigment_r;
  dmnsn_vector viewer;
  dmnsn_vector reflected;
  dmnsn_vector light;

  dmnsn_color pigment;
  dmnsn_color diffuse;
  dmnsn_color additional;

  double ior;

  dmnsn_color adc_value;
} dmnsn_rtstate;

/** Compute a ray-tracing state from an intersection. */
static inline void
dmnsn_rtstate_initialize(dmnsn_rtstate *state,
                         const dmnsn_intersection *intersection)
{
  state->intersection = intersection;
  state->texture      = intersection->object->texture;
  state->interior     = intersection->object->interior;

  state->r = dmnsn_line_point(intersection->ray, intersection->t);
  state->pigment_r = dmnsn_transform_point(
    intersection->object->pigment_trans,
    state->r
  );
  state->viewer = dmnsn_vector_normalized(
    dmnsn_vector_negate(intersection->ray.n)
  );
  state->reflected = dmnsn_vector_sub(
    dmnsn_vector_mul(
      2*dmnsn_vector_dot(state->viewer, intersection->normal),
      intersection->normal),
    state->viewer
  );

  state->pigment    = dmnsn_black;
  state->diffuse    = dmnsn_black;
  state->additional = dmnsn_black;
}

/** Main helper for dmnsn_ray_trace_scene_impl - shoot a ray. */
static dmnsn_color dmnsn_ray_shoot(dmnsn_rtstate *state, dmnsn_line ray);

/* Actually ray-trace a scene */
static int
dmnsn_ray_trace_scene_concurrent(void *ptr, unsigned int thread,
                                 unsigned int nthreads)
{
  const dmnsn_ray_trace_payload *payload = ptr;
  dmnsn_future *future = payload->future;
  dmnsn_scene *scene = payload->scene;
  dmnsn_prtree *prtree = payload->prtree;

  dmnsn_rtstate state = {
    .parent = NULL,
    .scene  = scene,
    .prtree = prtree,
  };

  /* Iterate through each pixel */
  for (size_t y = thread; y < scene->canvas->height; y += nthreads) {
    for (size_t x = 0; x < scene->canvas->width; ++x) {
      /* Get the ray corresponding to the (x,y)'th pixel */
      dmnsn_line ray = dmnsn_camera_ray(
        scene->camera,
        ((double)(x + scene->region_x))/(scene->outer_width - 1),
        ((double)(y + scene->region_y))/(scene->outer_height - 1)
      );

      /* Shoot a ray */
      state.reclevel = scene->reclimit;
      state.ior = 1.0;
      state.adc_value = dmnsn_white;
      dmnsn_color color = dmnsn_ray_shoot(&state, ray);

      dmnsn_canvas_set_pixel(scene->canvas, x, y, color);
    }

    dmnsn_future_increment(future);
  }

  return 0;
}

/** Calculate the background color. */
static dmnsn_color
dmnsn_trace_background(const dmnsn_rtstate *state, dmnsn_line ray)
{
  dmnsn_pigment *background = state->scene->background;
  if (state->scene->quality & DMNSN_RENDER_PIGMENT) {
    return dmnsn_pigment_evaluate(background, dmnsn_vector_normalized(ray.n));
  } else {
    return background->quick_color;
  }
}

/** Calculate the base pigment at the intersection. */
static void
dmnsn_trace_pigment(dmnsn_rtstate *state)
{
  dmnsn_pigment *pigment = state->texture->pigment;
  if (state->scene->quality & DMNSN_RENDER_PIGMENT) {
    state->pigment = dmnsn_pigment_evaluate(pigment, state->pigment_r);
  } else {
    state->pigment = pigment->quick_color;
  }

  state->diffuse = state->pigment;
}

/** Get the color of a light ray at an intersection point. */
static dmnsn_color
dmnsn_trace_light_ray(dmnsn_rtstate *state, const dmnsn_light *light)
{
  /** @todo: Start at the light source */
  dmnsn_line shadow_ray = dmnsn_new_line(
    state->r,
    light->direction_fn(light, state->r)
  );
  state->light = dmnsn_vector_normalized(shadow_ray.n);
  /* Add epsilon to avoid hitting ourselves with the shadow ray */
  shadow_ray = dmnsn_line_add_epsilon(shadow_ray);

  /* Check if we're casting a shadow on ourself */
  if (dmnsn_vector_dot(shadow_ray.n, state->intersection->normal)
      * dmnsn_vector_dot(state->viewer, state->intersection->normal) < 0.0)
    return dmnsn_black;

  dmnsn_color color = light->illumination_fn(light, state->r);

  /* Test for shadow ray intersections */
  unsigned int reclevel = state->reclevel;
  while (reclevel-- > 0
         && dmnsn_color_intensity(color) >= state->scene->adc_bailout)
  {
    dmnsn_intersection shadow_caster;
    bool shadow_was_cast = dmnsn_prtree_intersection(state->prtree, shadow_ray,
                                                     &shadow_caster, false);

    if (!shadow_was_cast || !light->shadow_fn(light, shadow_caster.t)) {
      return color;
    }

    /* Handle transparency */
    if (state->scene->quality & DMNSN_RENDER_TRANSPARENCY) {
      dmnsn_rtstate shadow_state = *state;
      dmnsn_rtstate_initialize(&shadow_state, &shadow_caster);
      dmnsn_trace_pigment(&shadow_state);

      if (shadow_state.pigment.trans >= dmnsn_epsilon) {
        /* Reflect the light */
        const dmnsn_reflection *reflection =
          shadow_state.texture->finish.reflection;
        if ((state->scene->quality & DMNSN_RENDER_REFLECTION) && reflection) {
          dmnsn_color reflected = reflection->reflection_fn(
            reflection, color, shadow_state.pigment, shadow_state.reflected,
            shadow_state.intersection->normal
          );
          color = dmnsn_color_sub(color, reflected);
        }

        /* Filter the light */
        color = dmnsn_filter_light(color, shadow_state.pigment);
        shadow_ray.x0 = dmnsn_line_point(shadow_ray, shadow_caster.t);
        shadow_ray.n  = light->direction_fn(light, shadow_ray.x0);
        shadow_ray = dmnsn_line_add_epsilon(shadow_ray);
        continue;
      }
    }

    break;
  }

  return dmnsn_black;
}

/** Handle light, shadow, and shading. */
static void
dmnsn_trace_lighting(dmnsn_rtstate *state)
{
  /* The ambient color */
  state->diffuse = dmnsn_black;

  const dmnsn_finish *finish = &state->texture->finish;
  if (finish->ambient) {
    state->diffuse =
      finish->ambient->ambient_fn(finish->ambient, state->pigment);
  }

  /* Iterate over each light */
  DMNSN_ARRAY_FOREACH (dmnsn_light **, light, state->scene->lights) {
    dmnsn_color light_color = dmnsn_trace_light_ray(state, *light);
    if (!dmnsn_color_is_black(light_color)) {
      if (state->scene->quality & DMNSN_RENDER_FINISH) {
        /* Reflect the light */
        const dmnsn_reflection *reflection = state->texture->finish.reflection;
        if ((state->scene->quality & DMNSN_RENDER_REFLECTION) && reflection) {
          dmnsn_color reflected = reflection->reflection_fn(
            reflection, light_color, state->pigment, state->reflected,
            state->intersection->normal
          );
          light_color = dmnsn_color_sub(light_color, reflected);
        }

        /* Get this light's color contribution to the object */
        dmnsn_color diffuse = dmnsn_black;
        if (finish->diffuse) {
          diffuse = finish->diffuse->diffuse_fn(
            finish->diffuse, light_color, state->pigment, state->light,
            state->intersection->normal
          );
        }

        dmnsn_color specular = dmnsn_black;
        if (finish->specular) {
          specular = finish->specular->specular_fn(
            finish->specular, light_color, state->pigment, state->light,
            state->intersection->normal, state->viewer
          );
        }

        state->diffuse = dmnsn_color_add(diffuse, state->diffuse);
        state->additional = dmnsn_color_add(specular, state->additional);
      } else {
        state->diffuse = state->pigment;
        state->diffuse.trans  = 0.0;
        state->diffuse.filter = 0.0;
      }
    }
  }
}

/** Trace a reflected ray. */
static dmnsn_color
dmnsn_trace_reflection(const dmnsn_rtstate *state)
{
  dmnsn_color reflected = dmnsn_black;

  const dmnsn_reflection *reflection = state->texture->finish.reflection;
  if (reflection) {
    dmnsn_line refl_ray = dmnsn_new_line(state->r, state->reflected);
    refl_ray = dmnsn_line_add_epsilon(refl_ray);

    dmnsn_rtstate recursive_state = *state;

    /* Calculate ADC value */
    recursive_state.adc_value = reflection->reflection_fn(
      reflection, state->adc_value, state->pigment, state->reflected,
      state->intersection->normal
    );

    /* Shoot the reflected ray */
    dmnsn_color rec = dmnsn_ray_shoot(&recursive_state, refl_ray);
    reflected = reflection->reflection_fn(
      reflection, rec, state->pigment, state->reflected,
      state->intersection->normal
    );
    reflected.trans  = 0.0;
    reflected.filter = 0.0;
  }

  return reflected;
}

/** Handle transparency - must be called last to work correctly. */
static void
dmnsn_trace_transparency(dmnsn_rtstate *state)
{
  if (state->pigment.trans >= dmnsn_epsilon) {
    dmnsn_line trans_ray = dmnsn_new_line(state->r, state->intersection->ray.n);
    trans_ray = dmnsn_line_add_epsilon(trans_ray);

    dmnsn_vector r = dmnsn_vector_normalized(trans_ray.n);
    dmnsn_vector n = state->intersection->normal;

    dmnsn_rtstate recursive_state = *state;

    /* Calculate new refractive index */
    if (dmnsn_vector_dot(r, n) < 0.0) {
      /* We are entering an object */
      recursive_state.ior = state->interior->ior;
      recursive_state.parent = state;
    } else {
      /* We are leaving an object */
      recursive_state.ior = state->parent ? state->parent->ior : 1.0;
      recursive_state.parent = state->parent ? state->parent->parent : NULL;
    }

    /* Calculate transmitted ray direction */
    double iorr = state->ior/recursive_state.ior; /* ior ratio */
    double c1 = -dmnsn_vector_dot(r, n);
    double c2 = 1.0 - iorr*iorr*(1.0 - c1*c1);
    if (c2 <= 0.0) {
      /* Total internal reflection */
      return;
    }
    c2 = sqrt(c2);
    if (c1 >= 0.0) {
      trans_ray.n = dmnsn_vector_add(
        dmnsn_vector_mul(iorr, r),
        dmnsn_vector_mul(iorr*c1 - c2, n)
      );
    } else {
      trans_ray.n = dmnsn_vector_add(
        dmnsn_vector_mul(iorr, r),
        dmnsn_vector_mul(iorr*c1 + c2, n)
      );
    }

    /* Calculate ADC value */
    recursive_state.adc_value =
      dmnsn_filter_light(state->adc_value, state->pigment);

    /* Shoot the transmitted ray */
    dmnsn_color rec = dmnsn_ray_shoot(&recursive_state, trans_ray);
    dmnsn_color filtered = dmnsn_filter_light(rec, state->pigment);

    /* Conserve energy */
    const dmnsn_reflection *reflection = state->texture->finish.reflection;
    if ((state->scene->quality & DMNSN_RENDER_REFLECTION) && reflection) {
      dmnsn_color reflected = reflection->reflection_fn(
        reflection, filtered, state->pigment, state->reflected,
        state->intersection->normal
      );
      filtered = dmnsn_color_sub(filtered, reflected);
    }

    state->diffuse.filter = state->pigment.filter;
    state->diffuse.trans  = state->pigment.trans;
    state->diffuse = dmnsn_apply_transparency(filtered, state->diffuse);
  }
}

/* Shoot a ray, and calculate the color */
static dmnsn_color
dmnsn_ray_shoot(dmnsn_rtstate *state, dmnsn_line ray)
{
  if (state->reclevel == 0
      || dmnsn_color_intensity(state->adc_value) < state->scene->adc_bailout)
  {
    return dmnsn_black;
  }

  --state->reclevel;

  dmnsn_intersection intersection;
  bool reset = state->reclevel == state->scene->reclimit - 1;
  if (dmnsn_prtree_intersection(state->prtree, ray, &intersection, reset)) {
    /* Found an intersection */
    dmnsn_rtstate_initialize(state, &intersection);

    /* Pigment */
    dmnsn_trace_pigment(state);

    /* Finishes and shadows */
    if (state->scene->quality & DMNSN_RENDER_LIGHTS) {
      dmnsn_trace_lighting(state);
    }

    /* Reflection */
    if (state->scene->quality & DMNSN_RENDER_REFLECTION) {
      state->additional = dmnsn_color_add(
        dmnsn_trace_reflection(state),
        state->additional
      );
    }

    /* Transparency */
    if (state->scene->quality & DMNSN_RENDER_TRANSPARENCY) {
      dmnsn_trace_transparency(state);
    }

    return dmnsn_color_add(state->diffuse, state->additional);
  } else {
    /* No intersection, return the background color */
    return dmnsn_trace_background(state, ray);
  }
}