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authorVito Caputo <vcaputo@pengaru.com>2017-05-27 09:46:49 -0700
committerVito Caputo <vcaputo@pengaru.com>2017-05-27 09:46:49 -0700
commit9ec2d061958458ff430073905397c2cb0df85a87 (patch)
tree038f8f4e2452dd5736db7b871dbb0544f47daa37 /src/modules/ray
parent28d8022265a12e5032ddb54077f90af9f1bcb4f5 (diff)
ray: use approximate power in specular reflection
powf() is slow but precise, this isn't the fastest method but it's at least portable and a bit faster.
Diffstat (limited to 'src/modules/ray')
-rw-r--r--src/modules/ray/ray_scene.c20
1 files changed, 16 insertions, 4 deletions
diff --git a/src/modules/ray/ray_scene.c b/src/modules/ray/ray_scene.c
index 87a77af..d9b8277 100644
--- a/src/modules/ray/ray_scene.c
+++ b/src/modules/ray/ray_scene.c
@@ -36,6 +36,16 @@ static inline int ray_is_obstructed(ray_scene_t *scene, ray_ray_t *ray, float di
}
+/* 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_ray(ray_scene_t *scene, ray_ray_t *ray, ray_object_t *object, float distance, unsigned depth)
{
@@ -82,10 +92,12 @@ static inline ray_color_t shade_ray(ray_scene_t *scene, ray_ray_t *ray, ray_obje
diffuse = ray_3f_mult_scalar(&diffuse, surface.diffuse);
color = ray_3f_add(&color, &diffuse);
- /* FIXME: assumes light is a point for its color */
- specular = ray_3f_mult_scalar(&scene->lights[i].light.emitter.point.surface.color, powf(rvec_lvec_dot, surface.highlight_exponent));
- specular = ray_3f_mult_scalar(&specular, surface.specular);
- color = ray_3f_add(&color, &specular);
+ if (rvec_lvec_dot > 0) {
+ /* 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;
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