1 files changed, 4 insertions, 28 deletions
diff --git a/intern/cycles/kernel/kernel_montecarlo.h b/intern/cycles/kernel/kernel_montecarlo.h
index 2ae95084162..f608429da36 100644
--- a/intern/cycles/kernel/kernel_montecarlo.h
+++ b/intern/cycles/kernel/kernel_montecarlo.h
@@ -36,36 +36,12 @@
 CCL_NAMESPACE_BEGIN
 
 /// Given values x and y on [0,1], convert them in place to values on
-/// [-1,1] uniformly distributed over a unit sphere.  This code is
-/// derived from Peter Shirley, "Realistic Ray Tracing", p. 103.
+/// [-1,1] uniformly distributed over a unit sphere.
 __device void to_unit_disk(float *x, float *y)
 {
-	float r, phi;
-	float a = 2.0f * (*x) - 1.0f;
-	float b = 2.0f * (*y) - 1.0f;
-	if(a > -b) {
-		if(a > b) {
-			r = a;
-			phi = M_PI_4_F *(b/a);
-		}
-		else {
-			r = b;
-			phi = M_PI_4_F *(2.0f - a/b);
-		}
-	}
-	else {
-		if(a < b) {
-			r = -a;
-			phi = M_PI_4_F *(4.0f + b/a);
-		}
-		else {
-			r = -b;
-			if(b != 0.0f)
-				phi = M_PI_4_F *(6.0f - a/b);
-			else
-				phi = 0.0f;
-		}
-	}
+	float phi = 2.0f * M_PI_F * (*x);
+	float r = sqrtf(*y);
+
 	*x = r * cosf(phi);
 	*y = r * sinf(phi);
 }