Guarding cotton weights.

In some instances weights dropped below zero.

Author: cheind

inc/deform/arap.h

@@ -119,6 +119,9 @@ namespace deform {
  _dirty = false;
  }
 
+ // Estimate positions
+ estimatePositions();
+ 
  for (Index i = 0; i < numberOfIterations; ++i) {
 
  // Estimate rotations
@@ -209,9 +212,13 @@ namespace deform {
 
  const Scalar denom = Scalar(1.0) / (Scalar(4.0) * area);
 
- const Scalar cot0 = (-l0 * l0 + l1 * l1 + l2 * l2) * denom;
- const Scalar cot1 = (l0 * l0 - l1 * l1 + l2 * l2) * denom;
- const Scalar cot2 = (l0 * l0 + l1 * l1 - l2 * l2) * denom;
+ Scalar cot0 = (-l0 * l0 + l1 * l1 + l2 * l2) * denom;
+ Scalar cot1 = (l0 * l0 - l1 * l1 + l2 * l2) * denom;
+ Scalar cot2 = (l0 * l0 + l1 * l1 - l2 * l2) * denom;
+ 
+ cot0 = std::max<Scalar>(Scalar(1e-8), cot0);
+ cot1 = std::max<Scalar>(Scalar(1e-8), cot1);
+ cot2 = std::max<Scalar>(Scalar(1e-8), cot2);
 
  std::pair<Index, Index> e0 = undirectedEdge(vids(0), vids(1));
  std::pair<Index, Index> e1 = undirectedEdge(vids(1), vids(2));