GPU subdiv: fix custom data interpolation for N-gons

Not all coarse vertices were used to compute the center value (off by
one), and the interpolation for the current would always start at the
base corner for the base face instead of the base corner for the current
patch.

1 files changed, 2 insertions, 2 deletions

diff --git a/source/blender/draw/intern/shaders/common_subdiv_custom_data_interp_comp.glsl b/source/blender/draw/intern/shaders/common_subdiv_custom_data_interp_comp.glsl
index 36c3970d9a0..df0016761e2 100644
--- a/source/blender/draw/intern/shaders/common_subdiv_custom_data_interp_comp.glsl
+++ b/source/blender/draw/intern/shaders/common_subdiv_custom_data_interp_comp.glsl
@@ -185,7 +185,7 @@ void main()
   }
   else {
     /* Interpolate the src data for the center. */
-    uint loop_end = loop_start + number_of_vertices - 1;
+    uint loop_end = loop_start + number_of_vertices;
     Vertex center_value;
     clear(center_value);
 
@@ -202,7 +202,7 @@ void main()
     uint prev_coarse_corner = (current_coarse_corner + number_of_vertices - 1) %
                               number_of_vertices;
 
-    v0 = read_vertex(loop_start);
+    v0 = read_vertex(loop_start + current_coarse_corner);
     v1 = average(v0, read_vertex(loop_start + next_coarse_corner));
     v3 = average(v0, read_vertex(loop_start + prev_coarse_corner));