/// <summary>
/// Creates one edge, two vertices and a loop (face).
/// The loop consists of the two new half-edges.
/// </summary>
public MeshUtils.Edge MakeEdge()
{
var e = MeshUtils.MakeEdge(_eHead);
MeshUtils.MakeVertex(new MeshUtils.Vertex(), e, _vHead);
MeshUtils.MakeVertex(new MeshUtils.Vertex(), e._Sym, _vHead);
MeshUtils.MakeFace(new MeshUtils.Face(), e, _fHead);
return(e);
}
/// <summary>
/// Creates a new edge such that eNew == eOrg.Lnext and eNew.Dst is a newly created vertex.
/// eOrg and eNew will have the same left face.
/// </summary>
public MeshUtils.Edge AddEdgeVertex(MeshUtils.Edge eOrg)
{
var eNew = MeshUtils.MakeEdge(eOrg);
var eNewSym = eNew._Sym;
// Connect the new edge appropriately
MeshUtils.Splice(eNew, eOrg._Lnext);
// Set vertex and face information
eNew._Org = eOrg._Dst;
MeshUtils.MakeVertex(new MeshUtils.Vertex(), eNewSym, eNew._Org);
eNew._Lface = eNewSym._Lface = eOrg._Lface;
return(eNew);
}
/// <summary>
/// Splice is the basic operation for changing the
/// mesh connectivity and topology. It changes the mesh so that
/// eOrg->Onext = OLD( eDst->Onext )
/// eDst->Onext = OLD( eOrg->Onext )
/// where OLD(...) means the value before the meshSplice operation.
///
/// This can have two effects on the vertex structure:
/// - if eOrg->Org != eDst->Org, the two vertices are merged together
/// - if eOrg->Org == eDst->Org, the origin is split into two vertices
/// In both cases, eDst->Org is changed and eOrg->Org is untouched.
///
/// Similarly (and independently) for the face structure,
/// - if eOrg->Lface == eDst->Lface, one loop is split into two
/// - if eOrg->Lface != eDst->Lface, two distinct loops are joined into one
/// In both cases, eDst->Lface is changed and eOrg->Lface is unaffected.
///
/// Some special cases:
/// If eDst == eOrg, the operation has no effect.
/// If eDst == eOrg->Lnext, the new face will have a single edge.
/// If eDst == eOrg->Lprev, the old face will have a single edge.
/// If eDst == eOrg->Onext, the new vertex will have a single edge.
/// If eDst == eOrg->Oprev, the old vertex will have a single edge.
/// </summary>
public void Splice(MeshUtils.Edge eOrg, MeshUtils.Edge eDst)
{
if (eOrg == eDst)
{
return;
}
bool joiningVertices = false;
if (eDst._Org != eOrg._Org)
{
// We are merging two disjoint vertices -- destroy eDst->Org
joiningVertices = true;
MeshUtils.KillVertex(eDst._Org, eOrg._Org);
}
bool joiningLoops = false;
if (eDst._Lface != eOrg._Lface)
{
// We are connecting two disjoint loops -- destroy eDst->Lface
joiningLoops = true;
MeshUtils.KillFace(eDst._Lface, eOrg._Lface);
}
// Change the edge structure
MeshUtils.Splice(eDst, eOrg);
if (!joiningVertices)
{
// We split one vertex into two -- the new vertex is eDst->Org.
// Make sure the old vertex points to a valid half-edge.
MeshUtils.MakeVertex(new MeshUtils.Vertex(), eDst, eOrg._Org);
eOrg._Org._anEdge = eOrg;
}
if (!joiningLoops)
{
// We split one loop into two -- the new loop is eDst->Lface.
// Make sure the old face points to a valid half-edge.
MeshUtils.MakeFace(new MeshUtils.Face(), eDst, eOrg._Lface);
eOrg._Lface._anEdge = eOrg;
}
}