/// <summary>
/// Split the face with Corner Cutting
/// </summary>
/// <param name="m">Polymesh</param>
/// <param name="heh">Half-edge for the Face</param>
/// <returns>New Face Handle</returns>
public static int CornerCutting(PolyMesh m, int heh)
{
int heh1 = heh,
heh5 = heh1,
heh6 = m.GetNextHalfedgeH(heh1);
// Cycle around the polygon to find correct Halfedge
for (; m.GetNextHalfedgeH(m.GetNextHalfedgeH(heh5)) != heh1;
heh5 = m.GetNextHalfedgeH(heh5))
{
}
int vh1 = m.GetEndVertexH(heh1),
vh2 = m.GetEndVertexH(heh5);
int heh2 = m.GetNextHalfedgeH(heh5),
heh3 = m.NewEdge(vh1, vh2),
heh4 = m.GetOppositeHalfedgeH(heh3);
/* Intermediate result
*
* *
* 5 /|\
* /_ \
* vh2> * *
* /|\3 |\
* 2 /_ \|4 \
* *----\*----\*
* 1 ^ 6
* vh1 (adjust_outgoing half - edge!)
*/
// Old and new Face
int fh_old = m.GetFaceH(heh6);
int fh_new = m.NewFace();
// Re-Set Handles around old Face
m.SetNextHalfedgeH(heh4, heh6);
m.SetNextHalfedgeH(heh5, heh4);
m.SetFaceH(heh4, fh_old);
m.SetFaceH(heh5, fh_old);
m.SetFaceH(heh6, fh_old);
m.SetHalfedgeFaceH(fh_old, heh4);
// Re-Set Handles around new Face
m.SetNextHalfedgeH(heh1, heh3);
m.SetNextHalfedgeH(heh3, heh2);
m.SetFaceH(heh1, fh_new);
m.SetFaceH(heh2, fh_new);
m.SetFaceH(heh3, fh_new);
m.SetHalfedgeFaceH(fh_new, heh1);
return(fh_new);
}
public static Vector3 ComputeMidPoint(PolyMesh m, int heh)
{
var opp_heh = m.GetOppositeHalfedgeH(heh);
Vector3 pos = m.GetPoint(m.GetEndVertexH(heh));
pos += m.GetPoint(m.GetEndVertexH(opp_heh));
if (m.IsBoundaryHalfedge(heh) || m.IsBoundaryHalfedge(opp_heh))
{
return(pos * 0.5f);
}
else
{
pos *= 3.0f;
pos += m.GetPoint(m.GetEndVertexH(m.GetNextHalfedgeH(heh)));
pos += m.GetPoint(m.GetEndVertexH(m.GetNextHalfedgeH(opp_heh)));
pos *= 0.125f;
}
return(pos);
}
/// <summary>
/// Split edge in half
/// </summary>
/// <param name="m">Polymesh</param>
/// <param name="eh">Edge Handle</param>
/// <returns>New Half-edge Handle for the new Edge</returns>
public static int SplitEdge(PolyMesh m, int eh)
{
int heh = m.GetHalfedgeEdgeH(eh, 0);
int opp_heh = m.GetHalfedgeEdgeH(eh, 1);
int new_heh, opp_new_heh, t_heh;
int vh, vh1 = m.GetEndVertexH(heh);
Vector3 midP = m.GetPoint(vh1);
midP += m.GetPoint(m.GetEndVertexH(opp_heh));
midP *= 0.5f;
// new vertex
vh = m.AddVertex(midP);
// Re-link mesh entities
if (m.IsBoundaryEdge(eh))
{
for (t_heh = heh;
m.GetNextHalfedgeH(t_heh) != opp_heh;
t_heh = m.GetOppositeHalfedgeH(m.GetNextHalfedgeH(t_heh)))
{
}
}
else
{
for (t_heh = m.GetNextHalfedgeH(opp_heh);
m.GetNextHalfedgeH(t_heh) != opp_heh;
t_heh = m.GetNextHalfedgeH(t_heh))
{
}
}
new_heh = m.NewEdge(vh, vh1);
opp_new_heh = m.GetOppositeHalfedgeH(new_heh);
m.SetVertexH(heh, vh);
m.SetNextHalfedgeH(t_heh, opp_new_heh);
m.SetNextHalfedgeH(new_heh, m.GetNextHalfedgeH(heh));
m.SetNextHalfedgeH(heh, new_heh);
m.SetNextHalfedgeH(opp_new_heh, opp_heh);
if (m.GetFaceH(opp_heh).isValidHandle())
{
m.SetFaceH(opp_new_heh, m.GetFaceH(opp_heh));
m.SetHalfedgeFaceH(m.GetFaceH(opp_new_heh), opp_new_heh);
}
m.SetFaceH(new_heh, m.GetFaceH(heh));
m.SetHalfedgeVertexH(vh, new_heh);
m.SetHalfedgeFaceH(m.GetFaceH(heh), heh);
m.SetHalfedgeVertexH(vh1, opp_new_heh);
// Never forget this, when playing with the topology
m.AdjustOutgoingHalfedge(vh);
m.AdjustOutgoingHalfedge(vh1);
return(new_heh);
}
