diff --git a/src/lib.rs b/src/lib.rs
index 457a3f1..9ae7d9d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -257,6 +257,9 @@ impl Core {
 			let mut value = 0.0f32;
 			for light_hit in &hits {
 				let d2 = hit.base.distance_squared(light_hit.base);
+				if d2 > 3. * sigma2 {
+					continue;
+				}
 				let w = (-0.5 * d2 / sigma2).exp();
 				value += w;
 			}