subdivide.cs

public ConwayPoly Subdivide(float offset)
{

    var faceIndices = new List<int[]>();
    var vertexPoints = new List<Vector3>();
    
    // Add existing vertices
    for (int vertexIndex = 0; vertexIndex < Vertices.Count; vertexIndex++)
    {
        var x = Vertices[vertexIndex];
        vertexPoints.Add(x.Position + x.Normal * offset);
    }

    // Create new vertices, one at the midpoint of each edge
    var newVertices = new Dictionary<(Guid, Guid)?, int>();
    int currentVertexIndex = vertexPoints.Count;

    foreach (var edge in Halfedges)
    {
        vertexPoints.Add(edge.Midpoint);
        newVertices[edge.PairedName] = currentVertexIndex++;
    }

    for (var faceIndex = 0; faceIndex < Faces.Count; faceIndex++)
    {
        var face = Faces[faceIndex];
        
        // Create a new face for each existing face
        var newFace = new int[face.Sides];
        var edge = face.Halfedge;

        for (int i = 0; i < face.Sides; i++)
        {
            newFace[i] = newVertices[edge.PairedName];
            edge = edge.Next;
        }

        faceIndices.Add(newFace);
    }

    // Create new faces for each vertex
    for (int idx = 0; idx < Vertices.Count; idx++)
    {
        var vertex = Vertices[idx];
        var adjacentFaces = vertex.GetVertexFaces();

        for (var faceIndex = 0; faceIndex < adjacentFaces.Count; faceIndex++)
        {
            Face face = adjacentFaces[faceIndex];
            var edge = face.GetHalfedges().Find(x => x.Vertex == vertex);
            int currVertex = newVertices[edge.PairedName];
            int prevVertex = newVertices[edge.Next.PairedName];
            var triangle = new[] {idx, prevVertex, currVertex};
            faceIndices.Add(triangle);

            var vertexFaceIndices = vertex.GetVertexFaces().Select(f => Faces.IndexOf(f));
        }
    }

    var poly = new ConwayPoly(vertexPoints, faceIndices);
    return poly;
}