From a778521c2f5cff7eb21c8f2153166753c328167c Mon Sep 17 00:00:00 2001
From: Andrew Clinton <ajclinto@gmail.com>
Date: Thu, 12 Sep 2013 16:36:45 -0400
Subject: [PATCH] Improve numerical stability of catmark subdivision

This change sums the vertex point last, since it's normally the largest
value.  There may be other numerical stability issues in this code that I
haven't discovered.
---
 opensubdiv/hbr/catmark.h | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/opensubdiv/hbr/catmark.h b/opensubdiv/hbr/catmark.h
index bde83759..47f446b5 100644
--- a/opensubdiv/hbr/catmark.h
+++ b/opensubdiv/hbr/catmark.h
@@ -1063,8 +1063,6 @@ HbrCatmarkSubdivision<T>::Subdivide(HbrMesh<T>* mesh, HbrVertex<T>* vertex) {
         switch (masks[i]) {
             case HbrVertex<T>::k_Smooth:
             case HbrVertex<T>::k_Dart: {
-                // Compute n-2/n of the old vertex value
-                data.AddWithWeight(vertex->GetData(), weights[i] * invvalencesquared * valence * (valence - 2));
                 // Add 1 / n^2 * surrounding edge vertices and surrounding face
                 // subdivided vertices
                 HbrSubdivision<T>::AddSurroundingVerticesWithWeight(
@@ -1078,16 +1076,18 @@ HbrCatmarkSubdivision<T>::Subdivide(HbrMesh<T>* mesh, HbrVertex<T>* vertex) {
                     edge = vertex->GetNextEdge(edge);
                     if (edge == start) break;
                 }
+                // Compute n-2/n of the old vertex value
+                data.AddWithWeight(vertex->GetData(), weights[i] * invvalencesquared * valence * (valence - 2));
                 break;
             }
             case HbrVertex<T>::k_Crease: {
-                // Compute 3/4 of old vertex value
-                data.AddWithWeight(vertex->GetData(), weights[i] * 0.75f);
-
                 // Add 0.125f of the (hopefully only two!) neighbouring
                 // sharp edges
                 HbrSubdivision<T>::AddCreaseEdgesWithWeight(
                     mesh, vertex, i == 1, weights[i] * 0.125f, &data);
+
+                // Compute 3/4 of old vertex value
+                data.AddWithWeight(vertex->GetData(), weights[i] * 0.75f);
                 break;
             }
             case HbrVertex<T>::k_Corner: