Fix T79803: Wrong Distance To Edge 1D Voronoi

The current 1D Voronoi implementation for the Distance to Edge option
computes the distance to the cells instead. This patch fixes that and
compute the distance to the edge.

Reviewed By: JacquesLucke, brecht

Differential Revision: https://developer.blender.org/D8634

1 files changed, 7 insertions, 8 deletions

diff --git a/intern/cycles/kernel/svm/svm_voronoi.h b/intern/cycles/kernel/svm/svm_voronoi.h
index f0fc0068fa2..10d17403f65 100644
--- a/intern/cycles/kernel/svm/svm_voronoi.h
+++ b/intern/cycles/kernel/svm/svm_voronoi.h
@@ -144,14 +144,13 @@ ccl_device void voronoi_distance_to_edge_1d(float w, float randomness, float *ou
   float cellPosition = floorf(w);
   float localPosition = w - cellPosition;
 
-  float minDistance = 8.0f;
-  for (int i = -1; i <= 1; i++) {
-    float cellOffset = i;
-    float pointPosition = cellOffset + hash_float_to_float(cellPosition + cellOffset) * randomness;
-    float distanceToPoint = fabsf(pointPosition - localPosition);
-    minDistance = min(distanceToPoint, minDistance);
-  }
-  *outDistance = minDistance;
+  float midPointPosition = hash_float_to_float(cellPosition) * randomness;
+  float leftPointPosition = -1.0f + hash_float_to_float(cellPosition - 1.0f) * randomness;
+  float rightPointPosition = 1.0f + hash_float_to_float(cellPosition + 1.0f) * randomness;
+  float distanceToMidLeft = fabsf((midPointPosition + leftPointPosition) / 2.0f - localPosition);
+  float distanceToMidRight = fabsf((midPointPosition + rightPointPosition) / 2.0f - localPosition);
+
+  *outDistance = min(distanceToMidLeft, distanceToMidRight);
 }
 
 ccl_device void voronoi_n_sphere_radius_1d(float w, float randomness, float *outRadius)