/// <overloads>
/// <summary>
/// Converts the given <see cref="ITriangleMesh"/> to a <see cref="DcelMesh"/>.
/// </summary>
/// </overloads>
///
/// <summary>
/// Converts the given <see cref="ITriangleMesh"/> to a <see cref="DcelMesh"/>.
/// </summary>
/// <param name="mesh">The triangle mesh.</param>
/// <returns>
/// The <see cref="DcelMesh"/>.
/// </returns>
/// <remarks>
/// Currently, creating <see cref="DcelMesh"/>es is not supported if the triangle mesh consists
/// of unconnected sub-meshes or unconnected triangles. All parts of the triangle mesh must be
/// connected via an edge. (But it is not required that the mesh is closed.)
/// </remarks>
/// <exception cref="ArgumentNullException">
/// <paramref name="mesh"/> is <see langword="null"/>.
/// </exception>
/// <exception cref="ArgumentException">
/// <paramref name="mesh"/> has no vertices or vertex indices.
/// </exception>
/// <exception cref="NotSupportedException">
/// <paramref name="mesh"/> consists of several unconnected components or sub-meshes.
/// </exception>
public static DcelMesh FromTriangleMesh(ITriangleMesh mesh)
{
if (mesh == null)
{
throw new ArgumentNullException("mesh");
}
// The simple way: Create a TriangleMesh first.
var triangleMesh = new TriangleMesh();
triangleMesh.Add(mesh, false);
triangleMesh.WeldVertices();
return(FromTriangleMesh(triangleMesh));
}
private void CreateDualGraph()
{
var triangles = new List <CDTriangle>();
// Convert to TriangleMesh.
var triangleMesh = _mesh as TriangleMesh;
if (triangleMesh == null)
{
triangleMesh = new TriangleMesh();
triangleMesh.Add(_mesh, false);
triangleMesh.WeldVertices();
}
// Initialize vertex normals.
var normals = new Vector3[triangleMesh.Vertices.Count]; // Vertex normals.
var neighborCounts = new int[triangleMesh.Vertices.Count]; // Numbers of triangles that touch each vertex.
for (int i = 0; i < triangleMesh.Vertices.Count; i++)
{
normals[i] = Vector3.Zero;
neighborCounts[i] = 0;
}
// Go through all triangles. Add the normal to normals and increase the neighborCounts
for (int i = 0; i < triangleMesh.NumberOfTriangles; i++)
{
Triangle triangle = triangleMesh.GetTriangle(i);
var normal = triangle.Normal;
for (int j = 0; j < 3; j++)
{
var vertexIndex = triangleMesh.Indices[(i * 3) + j];
normals[vertexIndex] = normals[vertexIndex] + normal;
neighborCounts[vertexIndex] = neighborCounts[vertexIndex] + 1;
}
}
// Create triangles.
for (int i = 0; i < triangleMesh.NumberOfTriangles; i++)
{
Triangle triangle = triangleMesh.GetTriangle(i);
var cdTriangle = new CDTriangle
{
Id = i,
Vertices = new[] { triangle.Vertex0, triangle.Vertex1, triangle.Vertex2 },
Normal = triangle.Normal, // TODO: Special care for degenerate triangles needed?
};
for (int j = 0; j < 3; j++)
{
var vertexIndex = triangleMesh.Indices[(i * 3) + j];
var normalSum = normals[vertexIndex];
var neighborCount = neighborCounts[vertexIndex];
if (neighborCount > 0)
{
var normal = normalSum / neighborCount;
normal.TryNormalize();
cdTriangle.VertexNormals[j] = normal;
}
}
triangles.Add(cdTriangle);
}
// Create an island for each triangle.
_islands = new List <CDIsland>(triangles.Count);
for (int i = 0; i < triangles.Count; i++)
{
var triangle = triangles[i];
var island = new CDIsland();
island.Id = i;
island.Triangles = new[] { triangle };
island.Vertices = triangle.Vertices;
island.Aabb = new Aabb(triangle.Vertices[0], triangle.Vertices[0]);
island.Aabb.Grow(triangle.Vertices[1]);
island.Aabb.Grow(triangle.Vertices[2]);
triangle.Island = island;
_islands.Add(island);
}
// Find connectivity (= add neighbor links).
for (int i = 0; i < triangles.Count; i++)
{
var a = triangles[i];
for (int j = i + 1; j < triangles.Count; j++)
{
var b = triangles[j];
CDTriangle.FindNeighbors(a, b);
}
}
// Create links.
_links = new List <CDIslandLink>();
for (int i = 0; i < _islands.Count; i++)
{
var island = _islands[i];
var triangle = island.Triangles[0];
// Go through all neighbors.
// If there is a neighbor, create a link.
// To avoid two links per triangle, we create the link only if the id of this triangle
// is less than the other island id.
for (int j = 0; j < 3; j++)
{
CDTriangle neighborTriangle = triangle.Neighbors[j];
if (neighborTriangle != null && neighborTriangle.Island.Id > i)
{
var link = new CDIslandLink(island, neighborTriangle.Island, AllowedConcavity, SmallIslandBoost, IntermediateVertexLimit, SampleTriangleVertices, SampleTriangleCenters);
_links.Add(link);
}
}
}
// Now, we have a lot of islands with 1 triangle each.
}
