computeEdgeCollapseCost static method

dynamic computeEdgeCollapseCost(dynamic u, dynamic v)

Implementation

static computeEdgeCollapseCost( u, v ) {
  // if we collapse edge uv by moving u to v then how
  // much different will the model change, i.e. the "error".
  final edgelength = v.position.distanceTo( u.position );
  double curvature = 0;

  final sideFaces = [];

  // find the "sides" triangles that are on the edge uv
  for (int i = 0, il = u.faces.length; i < il; i ++ ) {
    final Tri face = u.faces[ i ];
    if (face.hasVertex(v)) {
      sideFaces.add(face);
    }
  }

  // use the triangle facing most away from the sides
  // to determine our curvature term
  for (int i = 0, il = u.faces.length; i < il; i ++ ) {
    double minCurvature = 1;
    final Tri face = u.faces[i];

    for (int j = 0; j < sideFaces.length; j ++ ) {
      final sideFace = sideFaces[j];
      // use dot product of face normals.
      double dotProd = face.normal.dot(sideFace.normal).toDouble();
      minCurvature = Math.min( minCurvature, ( 1.001 - dotProd ) / 2 );
    }

    curvature = Math.max( curvature, minCurvature );
  }

  // crude approach in attempt to preserve borders
  // though it seems not to be totally correct
  const borders = 0;

  if ( sideFaces.length < 2 ) {
    // we add some arbitrary cost for borders,
    // borders += 10;
    curvature = 1;
  }

  final amt = edgelength * curvature + borders;

  return amt;
}