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
|
#include <stdlib.h>
#include <math.h>
#include "fb.h"
#include "ray_camera.h"
#include "ray_color.h"
#include "ray_object.h"
#include "ray_ray.h"
#include "ray_scene.h"
#define MAX_RECURSION_DEPTH 4
/* Determine if the ray is obstructed by an object within the supplied distance, for shadows */
static inline int ray_is_obstructed(ray_scene_t *scene, unsigned depth, ray_ray_t *ray, float distance)
{
unsigned i;
for (i = 0; i < scene->n_objects; i++) {
float ood;
if (ray_object_intersects_ray(&scene->objects[i], depth, ray, &ood) &&
ood < distance) {
return 1;
}
}
return 0;
}
/* shadow test */
static inline int point_is_shadowed(ray_scene_t *scene, unsigned depth, ray_3f_t *light_direction, float distance, ray_3f_t *point)
{
ray_ray_t shadow_ray;
shadow_ray.direction = *light_direction;
shadow_ray.origin = *point;
if (ray_is_obstructed(scene, depth + 1, &shadow_ray, distance))
return 1;
return 0;
}
/* a faster powf() that's good enough for our purposes.
* XXX: note there's a faster technique which exploits the IEEE floating point format:
* https://github.com/ekmett/approximate/blob/master/cbits/fast.c#L185
*/
static inline float approx_powf(float x, float y)
{
return expf(y * logf(x));
}
/* Determine the color @ distance on ray on object viewed from origin */
static inline ray_color_t shade_intersection(ray_scene_t *scene, ray_object_t *object, ray_ray_t *ray, ray_3f_t *intersection, ray_3f_t *normal, unsigned depth, float *res_reflectivity)
{
ray_surface_t surface = ray_object_surface(object, intersection);
ray_color_t color = ray_3f_mult(&surface.color, &scene->_prepared.ambient_light);
unsigned i;
/* visit lights for shadows and illumination */
for (i = 0; i < scene->n_lights; i++) {
ray_3f_t lvec = ray_3f_sub(&scene->lights[i].light.emitter.point.center, intersection);
float ldist = ray_3f_length(&lvec);
float lvec_normal_dot;
lvec = ray_3f_mult_scalar(&lvec, (1.0f / ldist)); /* normalize lvec */
#if 1
if (point_is_shadowed(scene, depth, &lvec, ldist, intersection))
continue;
#endif
lvec_normal_dot = ray_3f_dot(normal, &lvec);
if (lvec_normal_dot > 0) {
#if 1
float rvec_lvec_dot = ray_3f_dot(&ray->direction, &lvec);
ray_color_t diffuse;
diffuse = ray_3f_mult_scalar(&surface.color, lvec_normal_dot);
diffuse = ray_3f_mult_scalar(&diffuse, surface.diffuse);
color = ray_3f_add(&color, &diffuse);
if (rvec_lvec_dot > 0) {
ray_color_t specular;
/* FIXME: assumes light is a point for its color */
specular = ray_3f_mult_scalar(&scene->lights[i].light.emitter.point.surface.color, approx_powf(rvec_lvec_dot, surface.highlight_exponent));
specular = ray_3f_mult_scalar(&specular, surface.specular);
color = ray_3f_add(&color, &specular);
}
#else
ray_color_t diffuse;
diffuse = ray_3f_mult_scalar(&surface.color, lvec_normal_dot);
color = ray_3f_add(&color, &diffuse);
#endif
}
}
/* for now just treat specular as the reflectivity */
*res_reflectivity = surface.specular;
return color;
}
static inline ray_object_t * find_nearest_intersection(ray_scene_t *scene, ray_object_t *reflector, ray_ray_t *ray, unsigned depth, float *res_distance)
{
ray_object_t *nearest_object = NULL;
float nearest_object_distance = INFINITY;
unsigned i;
for (i = 0; i < scene->n_objects; i++) {
ray_object_t *object = &scene->objects[i];
float distance;
/* Don't bother checking if a reflected ray intersects the object reflecting it,
* reflector = NULL for primary rays, which will never compare as true here. */
if (object == reflector)
continue;
/* Does this ray intersect object? */
if (ray_object_intersects_ray(object, depth, ray, &distance)) {
/* Is it the nearest intersection? */
if (distance < nearest_object_distance) {
nearest_object = object;
nearest_object_distance = distance;
}
}
}
if (nearest_object)
*res_distance = nearest_object_distance;
return nearest_object;
}
static inline ray_color_t trace_ray(ray_scene_t *scene, ray_ray_t *primary_ray)
{
ray_color_t color = { .x = 0.0f, .y = 0.0f, .z = 0.0f };
ray_3f_t intersection, normal;
ray_object_t *reflector = NULL;
float relevance = 1.0f, reflectivity;
unsigned depth = 0;
ray_ray_t reflected_ray, *ray = primary_ray;
do {
ray_object_t *nearest_object;
float nearest_distance;
if (reflector) {
float dot = ray_3f_dot(&ray->direction, &normal);
ray_3f_t new_direction = ray_3f_mult_scalar(&normal, dot * 2.0f);
new_direction = ray_3f_sub(&ray->direction, &new_direction);
reflected_ray.origin = intersection;
reflected_ray.direction = new_direction;
ray = &reflected_ray;
relevance *= reflectivity;
}
nearest_object = find_nearest_intersection(scene, reflector, ray, depth, &nearest_distance);
if (nearest_object) {
ray_3f_t more_color;
ray_3f_t rvec;
rvec = ray_3f_mult_scalar(&ray->direction, nearest_distance);
intersection = ray_3f_add(&ray->origin, &rvec);
normal = ray_object_normal(nearest_object, &intersection);
more_color = shade_intersection(scene, nearest_object, ray, &intersection, &normal, depth, &reflectivity);
more_color = ray_3f_mult_scalar(&more_color, relevance);
color = ray_3f_add(&color, &more_color);
}
reflector = nearest_object;
} while (reflector && (++depth < MAX_RECURSION_DEPTH));
return color;
}
void ray_scene_render_fragment(ray_scene_t *scene, ray_camera_t *camera, fb_fragment_t *fragment)
{
ray_camera_frame_t frame;
ray_ray_t ray;
uint32_t *buf = fragment->buf;
unsigned stride = fragment->stride / 4;
ray_camera_frame_begin(camera, fragment, &ray, &frame);
do {
do {
*buf = ray_color_to_uint32_rgb(trace_ray(scene, &ray));
buf++;
} while (ray_camera_frame_x_step(&frame));
buf += stride;
} while (ray_camera_frame_y_step(&frame));
}
/* prepare the scene for rendering with camera, must be called whenever anything in the scene+camera pair has been changed. */
/* this is basically a time for the raytracer to precompute whatever it can which otherwise ends up occurring per-ray */
/* the camera is included so primary rays which all have a common origin may be optimized for */
void ray_scene_prepare(ray_scene_t *scene, ray_camera_t *camera)
{
unsigned i;
scene->_prepared.ambient_light = ray_3f_mult_scalar(&scene->ambient_color, scene->ambient_brightness);
for (i = 0; i < scene->n_objects; i++)
ray_object_prepare(&scene->objects[i], camera);
}
|
