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/source/blender/gpu/shaders/material/gpu_shader_material_tex_voronoi.glsl b/source/blender/gpu/shaders/material/gpu_shader_material_tex_voronoi.glsl
index 0d8847176c9..470ce1a1fa7 100644
--- a/source/blender/gpu/shaders/material/gpu_shader_material_tex_voronoi.glsl
+++ b/source/blender/gpu/shaders/material/gpu_shader_material_tex_voronoi.glsl
@@ -158,14 +158,13 @@ void node_tex_voronoi_distance_to_edge_1d(vec3 coord,
   float cellPosition = floor(scaledCoord);
   float localPosition = scaledCoord - cellPosition;
 
-  float minDistance = 8.0;
-  for (int i = -1; i <= 1; i++) {
-    float cellOffset = float(i);
-    float pointPosition = cellOffset + hash_float_to_float(cellPosition + cellOffset) * randomness;
-    float distanceToPoint = voronoi_distance(pointPosition, localPosition, metric, exponent);
-    minDistance = min(distanceToPoint, minDistance);
-  }
-  outDistance = minDistance;
+  float midPointPosition = hash_float_to_float(cellPosition) * randomness;
+  float leftPointPosition = -1.0 + hash_float_to_float(cellPosition - 1.0) * randomness;
+  float rightPointPosition = 1.0 + hash_float_to_float(cellPosition + 1.0) * randomness;
+  float distanceToMidLeft = distance((midPointPosition + leftPointPosition) / 2.0, localPosition);
+  float distanceToMidRight = distance((midPointPosition + rightPointPosition) / 2.0, localPosition);
+
+  outDistance = min(distanceToMidLeft, distanceToMidRight);
 }
 
 void node_tex_voronoi_n_sphere_radius_1d(vec3 coord,