Add camera aperture / depth-of-field

src/render.c

@@ -94,9 +94,19 @@ static int render_thread(void *arg)
 				    vec3_scale(camera->y_step, jitter.y));
 				const vec3_t jittered_pix = vec3_add(pix, offset);
 
+				vec3_t source = camera->pos;
+				if (camera->aperture != 0.0) {
+					const vec3_t pos
+					    = vec3_scale(rng_xy(&slice->rng), camera->aperture);
+					const vec3_t offset = vec3_add(
+					    vec3_scale(camera->u_hat, pos.x),
+					    vec3_scale(camera->v_hat, pos.y));
+					source = vec3_add(source, offset);
+				}
+
 				const ray_t ray = {
-					.orig = camera->pos,
-					.dir = vec3_unit(vec3_sub(jittered_pix, camera->pos)),
+					.orig = source,
+					.dir = vec3_unit(vec3_sub(jittered_pix, source)),
 				};
 				const vec3_t sample = trace(ray, slice->scene, &slice->rng);