private static void CreateTrianglesFromOneVertices(CutMesh mesh, int v1Index, int v2Index, int v3Index, MeshTriangle triangle, Plane plane, int subMesh)
{
var v1In = triangle.Vertices[v1Index];
var v2Out = triangle.Vertices[v2Index];
var v3Out = triangle.Vertices[v3Index];
var v1ToV2Point = MeshVertex.InterpolateVertexOnPlane(v1In, v2Out, plane);
var v1ToV3Point = MeshVertex.InterpolateVertexOnPlane(v1In, v3Out, plane);
// create triangle
mesh.AddTriangle(v1In, v1ToV2Point, v1ToV3Point, subMesh);
}
/// <summary>
/// Perform a cut on a specific mesh, using the under-laying properties.
/// </summary>
/// <param name="vertices"></param>
/// <param name="normals"></param>
/// <param name="tangents"></param>
/// <param name="uv"></param>
/// <param name="subMeshes"></param>
/// <param name="cutPlane"></param>
/// <returns></returns>
public static CutMesh[] PerformCut(List <Vector3> vertices, List <Vector3> normals, List <Vector4> tangents, List <Vector2> uv,
List <int>[] subMeshes, Plane cutPlane)
{
var subMeshesCount = subMeshes.Length;
var leftMesh = new CutMesh(subMeshesCount);
var rightMesh = new CutMesh(subMeshesCount);
// iterate triangles
for (var subMesh = 0; subMesh < subMeshesCount; subMesh++)
{
var meshIndices = subMeshes[subMesh];
for (var indicesIndex = 0; indicesIndex < meshIndices.Count - 2; indicesIndex += 3)
{
var v1Index = meshIndices[indicesIndex];
var v2Index = meshIndices[indicesIndex + 1];
var v3Index = meshIndices[indicesIndex + 2];
var triangle = new MeshTriangle(v1Index, v2Index, v3Index, vertices, normals, tangents, uv);
var v1Side = cutPlane.GetSide(triangle.Vertices[0].Point);
var v2Side = cutPlane.GetSide(triangle.Vertices[1].Point);
var v3Side = cutPlane.GetSide(triangle.Vertices[2].Point);
// add to proper sides
if (v1Side && v2Side && v3Side)
{
rightMesh.AddTriangle(triangle, subMesh);
continue;
}
if (!v1Side && !v2Side && !v3Side)
{
leftMesh.AddTriangle(triangle, subMesh);
continue;
}
if (v1Side == v2Side)
{
if (v1Side)
{
CreateTrianglesFromTwoVertices(rightMesh, 0, 1, 2, triangle, cutPlane, subMesh);
CreateTrianglesFromOneVertices(leftMesh, 2, 0, 1, triangle, cutPlane, subMesh);
continue;
}
CreateTrianglesFromTwoVertices(leftMesh, 0, 1, 2, triangle, cutPlane, subMesh);
CreateTrianglesFromOneVertices(rightMesh, 2, 0, 1, triangle, cutPlane, subMesh);
continue;
}
if (v2Side == v3Side)
{
if (v2Side)
{
CreateTrianglesFromTwoVertices(rightMesh, 1, 2, 0, triangle, cutPlane, subMesh);
CreateTrianglesFromOneVertices(leftMesh, 0, 1, 2, triangle, cutPlane, subMesh);
continue;
}
CreateTrianglesFromTwoVertices(leftMesh, 1, 2, 0, triangle, cutPlane, subMesh);
CreateTrianglesFromOneVertices(rightMesh, 0, 1, 2, triangle, cutPlane, subMesh);
continue;
}
// last possibility, v3Side == v1Side
if (v1Side)
{
CreateTrianglesFromTwoVertices(rightMesh, 2, 0, 1, triangle, cutPlane, subMesh);
CreateTrianglesFromOneVertices(leftMesh, 1, 2, 0, triangle, cutPlane, subMesh);
continue;
}
CreateTrianglesFromTwoVertices(leftMesh, 2, 0, 1, triangle, cutPlane, subMesh);
CreateTrianglesFromOneVertices(rightMesh, 1, 2, 0, triangle, cutPlane, subMesh);
}
}
return(new[] { leftMesh, rightMesh });
}