diff --git a/ref_vk/shaders/ray.rgen b/ref_vk/shaders/ray.rgen
index 2c41c1bb..063e7e73 100644
--- a/ref_vk/shaders/ray.rgen
+++ b/ref_vk/shaders/ray.rgen
@@ -12,6 +12,7 @@ const float shadow_offset_fudge = .1;
 const float pdf_culling_threshold = 100.;
 const float color_factor = 600.;
 const float color_culling_threshold = 600./color_factor;
+const float throughput_threshold = 1e-3;
 
 layout (constant_id = 4) const float LIGHT_GRID_CELL_SIZE = 256.;
 layout (constant_id = 5) const uint MAX_LIGHT_CLUSTERS = 32768;
@@ -404,6 +405,7 @@ void main() {
 		material.baseColor = payload_opaque.base_color;
 		material.metalness = 0.f; // TODO
 		material.emissive = payload_opaque.emissive;
+		//material.roughness = uintToFloat01(xxhash32(uvec3(floor(payload_opaque.hit_pos_t.xyz/64.)))); //payload_opaque.roughness;
 		material.roughness = payload_opaque.roughness;
 
 		if (bounce == 0) { //brdfType == SPECULAR_TYPE)
@@ -475,7 +477,7 @@ void main() {
 		}
 
 		throughput *= brdfWeight;
-		if (dot(throughput, throughput) < color_culling_threshold)
+		if (dot(throughput, throughput) < throughput_threshold)
 			break;
 
 		origin = payload_opaque.hit_pos_t.xyz;