// Get all half-edges going out from a vertex
public static List <short> VertexHalfEdges(HEVertex vertex, List <HalfEdge> halfEdges)
{
List <short> halfEdgeIndices = new List <short>();
short first = vertex.heIndex;
short next = halfEdges[halfEdges[first].oppositeIndex].nextIndex;
halfEdgeIndices.Add(first);
while (next != first)
{
halfEdgeIndices.Add(next);
next = halfEdges[halfEdges[next].oppositeIndex].nextIndex;
}
return(halfEdgeIndices);
}
public static void CreateStructureFromMesh(Mesh mesh, List <HalfEdge> halfEdges, List <HEFace> faces, List <HEVertex> vertices)
{
int[] meshTriangles = mesh.triangles;
Vector3[] meshVertices = mesh.vertices;
Vector3[] meshNormals = mesh.normals;
// One face per triangle. Add normals
for (int i = 0; i < meshTriangles.Length; i += 3)
{
HEFace f = new HEFace();
// Take the mean of the triangle normals
Vector3 n = meshNormals[meshTriangles[i]] + meshNormals[meshTriangles[i + 1]] + meshNormals[meshTriangles[i + 2]];
n = n / 3.0f;
f.normal = n.normalized;
faces.Add(f);
}
// Simplify mesh vertices i.e. remove duplicates.
// There are duplicate vertices since they have different normals
// Use a dictionary to store the vertices and their new indices
Dictionary <Vector3, int> d = new Dictionary <Vector3, int>();
List <Vector3> newVerts = new List <Vector3>();
List <int> newTris = new List <int>();
int newIdx = 0;
for (int i = 0; i < meshVertices.Length; i++)
{
if (!d.ContainsKey(meshVertices[i]))
{
d[meshVertices[i]] = newIdx;
newVerts.Add(meshVertices[i]);
newIdx++;
}
}
// Update the triangle indices to the new vertex indices.
for (int i = 0; i < meshTriangles.Length; i++)
{
newTris.Add(d[meshVertices[meshTriangles[i]]]);
}
// Set to updated values
meshVertices = newVerts.ToArray();
meshTriangles = newTris.ToArray();
// Init the vertices with vertex data, but not half-edge
for (int i = 0; i < meshVertices.Length; i++)
{
HEVertex vert = new HEVertex
{
v = meshVertices[i]
};
vertices.Add(vert);
}
// Dictionary for opposite lookup. Build in first loop over triangles, used in the second.
// key is v0v1
Dictionary <string, List <short> > edgeMap = new Dictionary <string, List <short> >();
// Start with creating the halfedges and filling in everything except oppositite
for (int i = 0; i < meshTriangles.Length; i += 3)
{
// Stored 3-by-3 indices. e.g. 0,1,2 forms the first triangle.
short i0 = (short)i;
short i1 = (short)(i + 1);
short i2 = (short)(i + 2);
// Triangles are in clockwise order in Unity
HalfEdge h0 = new HalfEdge();
HalfEdge h1 = new HalfEdge();
HalfEdge h2 = new HalfEdge();
h0.index = i0;
h1.index = i1;
h2.index = i2;
h0.faceIndex = i0;
h1.faceIndex = i0;
h2.faceIndex = i0;
h0.verIndex = (short)meshTriangles[i];
h1.verIndex = (short)meshTriangles[i + 1];
h2.verIndex = (short)meshTriangles[i + 2];
// Set the vertices halfedge index. It doesn't matter if we overwrite previously set values.
vertices[meshTriangles[i]].heIndex = i0;
vertices[meshTriangles[i + 1]].heIndex = i1;
vertices[meshTriangles[i + 2]].heIndex = i2;
// next entries. Unity wants clockwise order of vertices
h0.nextIndex = h1.index;
h1.nextIndex = h2.index;
h2.nextIndex = h0.index;
// Add them!
halfEdges.Add(h0);
halfEdges.Add(h1);
halfEdges.Add(h2);
// set face HalfEdge index. i0 is a multiple of 3
faces[i0 / 3].heIndex = i0;
// Fill edgemap, three times :)
string sum;
// This check is required so the ordering is consistent
if (h0.verIndex >= h1.verIndex)
{
sum = h0.verIndex.ToString() + h1.verIndex.ToString();
}
else
{
sum = h1.verIndex.ToString() + h0.verIndex.ToString();
}
if (!edgeMap.ContainsKey(sum))
{
List <short> l = new List <short>();
// add the face index
l.Add(i0);
edgeMap.Add(sum, l);
}
else
{
edgeMap[sum].Add(i0);
}
if (h1.verIndex >= h2.verIndex)
{
sum = h1.verIndex.ToString() + h2.verIndex.ToString();
}
else
{
sum = h2.verIndex.ToString() + h1.verIndex.ToString();
}
if (!edgeMap.ContainsKey(sum))
{
List <short> l = new List <short>();
// add the face index
l.Add(i1);
edgeMap.Add(sum, l);
}
else
{
edgeMap[sum].Add(i1);
}
if (h0.verIndex >= h2.verIndex)
{
sum = h0.verIndex.ToString() + h2.verIndex.ToString();
}
else
{
sum = h2.verIndex.ToString() + h0.verIndex.ToString();
}
if (!edgeMap.ContainsKey(sum))
{
List <short> l = new List <short>();
// add the face index
l.Add(i2);
edgeMap.Add(sum, l);
}
else
{
edgeMap[sum].Add(i2);
}
}
// Fill the opposite entries
for (int i = 0; i < meshTriangles.Length; i += 3)
{
// each edge is shared between exactly two faces
// Stored 3-by-3 indices. e.g. 0,1,2 forms the first triangle.
short i0 = (short)i;
short i1 = (short)(i + 1);
short i2 = (short)(i + 2);
HalfEdge h0 = halfEdges[i0];
HalfEdge h1 = halfEdges[i1];
HalfEdge h2 = halfEdges[i2];
// First edge
// Use our edgeMap to find opposites
string sum;
if (h0.verIndex >= h1.verIndex)
{
sum = h0.verIndex.ToString() + h1.verIndex.ToString();
}
else
{
sum = h1.verIndex.ToString() + h0.verIndex.ToString();
}
List <short> l = edgeMap[sum];
short h0Idx = l[0];
short h1Idx = l[1];
halfEdges[h0Idx].oppositeIndex = h1Idx;
halfEdges[h1Idx].oppositeIndex = h0Idx;
// Second edge
if (h1.verIndex >= h2.verIndex)
{
sum = h1.verIndex.ToString() + h2.verIndex.ToString();
}
else
{
sum = h2.verIndex.ToString() + h1.verIndex.ToString();
}
l = edgeMap[sum];
h0Idx = l[0];
h1Idx = l[1];
halfEdges[h0Idx].oppositeIndex = h1Idx;
halfEdges[h1Idx].oppositeIndex = h0Idx;
// Third edge
if (h0.verIndex >= h2.verIndex)
{
sum = h0.verIndex.ToString() + h2.verIndex.ToString();
}
else
{
sum = h2.verIndex.ToString() + h0.verIndex.ToString();
}
l = edgeMap[sum];
h0Idx = l[0];
h1Idx = l[1];
halfEdges[h0Idx].oppositeIndex = h1Idx;
halfEdges[h1Idx].oppositeIndex = h0Idx;
}
}