public static void ComputeCornerArea(TriMesh mesh, out double[] CornerArea, out double[] PointArea)
{
CornerArea = new double[mesh.HalfEdges.Count];
PointArea = new double[mesh.Vertices.Count];
foreach (var face in mesh.Faces)
{
double area = TriMeshUtil.ComputeAreaFace(face);
TriMesh.HalfEdge[] hf = new HalfEdgeMesh.HalfEdge[]
{
face.HalfEdge,
face.HalfEdge.Next,
face.HalfEdge.Previous
};
int[] index = new int[3];
for (int i = 0; i < 3; i++)
{
index[i] = hf[i].Index;
}
Vector3D[] e = new Vector3D[3];
for (int i = 0; i < 3; i++)
{
e[i] = TriMeshUtil.GetHalfEdgeVector(hf[i].Previous);
}
double[] l2 = new double[3];
for (int i = 0; i < 3; i++)
{
l2[i] = e[i].LengthSquared;
}
double[] ew = new double[3];
for (int i = 0; i < 3; i++)
{
ew[i] = l2[i] * (l2[(i + 1) % 3] + l2[(i + 2) % 3] - l2[i]);
}
bool flag = false;
for (int i = 0; i < 3; i++)
{
if (ew[i] < 0d)
{
int a = (i + 1) % 3;
int b = (i + 2) % 3;
CornerArea[index[a]] = -0.25d * l2[b] * area / e[i].Dot(e[b]);
CornerArea[index[b]] = -0.25d * l2[a] * area / e[i].Dot(e[a]);
CornerArea[index[i]] = area - CornerArea[index[a]] - CornerArea[index[b]];
flag = true;
}
}
if (!flag)
{
double ewscale = 0.5d * area / (ew[0] + ew[1] + ew[2]);
for (int i = 0; i < 3; i++)
{
CornerArea[index[i]] = ewscale * (ew[(i + 1) % 3] + ew[(i + 2) % 3]);
}
}
for (int i = 0; i < 3; i++)
{
PointArea[hf[i].ToVertex.Index] += CornerArea[index[i]];
}
}
}