diff --git a/src/trace.wgsl b/src/trace.wgsl
index cba8e84..1e4d264 100644
--- a/src/trace.wgsl
+++ b/src/trace.wgsl
@@ -122,9 +122,9 @@ fn rand_float() -> f32 {
 
 fn rand_sphere() -> vec3f {
 	loop {
-		let v = vec3f(rand_float(), rand_float(), rand_float());
+		let v = vec3f(rand_float(), rand_float(), rand_float()) - 0.5;
 		let l = length(v);
-		if (length(v) <= 1.0) {
+		if (length(v) <= 0.5) {
 			return v / l;
 		}
 	}