// After remeshing we may create an internal edge between two boundary vertices [a,b].
// Those vertices will be merged with vertices c and d in the base mesh. If the edge
// [c,d] already exists in the base mesh, then after the merge we would have at least
// 3 triangles at this edge. Dang.
//
// A common example is a 'fin' triangle that would duplicate a
// 'fin' on the border of the base mesh after removing the submesh, but this situation can
// arise anywhere (eg think about one-triangle-wide strips).
//
// This is very hard to remove, but we can at least avoid creating non-manifold edges (which
// with the current DMesh3 will be prevented, hence leaving a hole) by splitting the
// internal edge in the submesh (which presumably we were remeshing anyway, so changes are ok).
public void RepairPossibleNonManifoldEdges()
{
// [TODO] do we need to repeat this more than once? I don't think so...
// repair submesh
int NE = Region.SubMesh.MaxEdgeID;
var split_edges = new List <int>();
for (int eid = 0; eid < NE; ++eid)
{
if (Region.SubMesh.IsEdge(eid) == false)
{
continue;
}
if (Region.SubMesh.IsBoundaryEdge(eid))
{
continue;
}
Index2i edgev = Region.SubMesh.GetEdgeV(eid);
if (Region.SubMesh.IsBoundaryVertex(edgev.a) && Region.SubMesh.IsBoundaryVertex(edgev.b))
{
// ok, we have an internal edge where both verts are on the boundary
// now check if it is an edge in the base mesh
int base_a = Region.MapVertexToBaseMesh(edgev.a);
int base_b = Region.MapVertexToBaseMesh(edgev.b);
if (base_a != DMesh3.InvalidID && base_b != DMesh3.InvalidID)
{
// both vertices in base mesh...right?
Debug.Assert(Region.BaseMesh.IsVertex(base_a) && Region.BaseMesh.IsVertex(base_b));
int base_eid = Region.BaseMesh.FindEdge(base_a, base_b);
if (base_eid != DMesh3.InvalidID)
{
split_edges.Add(eid);
}
}
}
}
// split any problem edges we found and repeat this loop
for (int i = 0; i < split_edges.Count; ++i)
{
DMesh3.EdgeSplitInfo split_info;
Region.SubMesh.SplitEdge(split_edges[i], out split_info);
}
}
