Add reflective material

src/material.c

@@ -10,3 +10,17 @@ bool scatter_lambertian(
 	*atten_out = params.lambertian.albedo;
 	return true;
 }
+
+bool scatter_reflective(
+    material_params_t params, hit_t hit, rng_t *rng, ray_t *ray,
+    vec3_t *atten_out)
+{
+	(void)rng;
+
+	const vec3_t dn
+	    = vec3_scale(hit.normal, -2 * vec3_dot(hit.normal, ray->dir));
+	ray->orig = hit.point;
+	ray->dir = vec3_unit(vec3_add(ray->dir, dn));
+	*atten_out = params.reflective.tint;
+	return true;
+}