/// <summary>
/// This function tries to remove vertices from loop to hit TargetVtxCount. We call this
/// when polygon-insertion returns more vertices than polygon. Strategy is to try to find
/// co-linear vertices, ie that can be removed without changing shape. If that fails,
/// we remove vertices that result in smallest length change (probably should do proper simplification
/// here instead).
///
/// Basically this is to handle failures in MeshInsertUVPolyCurve.Simplify(), which sometimes
/// fails to remove extra vertices because it would case triangle flips. Here we don't
/// care about triangle flips.
///
/// Note that if the input polygon had splits on edges, this function would remove those
/// vertices. Which is not ideal.
/// </summary>
protected EdgeLoop simplify_loop(DMesh3 mesh, EdgeLoop loop, int TargetVtxCount)
{
while (loop.VertexCount > TargetVtxCount)
{
DCurve3 curve = loop.ToCurve();
DMesh3.EdgeCollapseInfo cinfo;
int NV = loop.VertexCount;
for (int k = 1; k <= NV; ++k)
{
int prevv = k - 1;
int curv = k % NV;
int nextv = (k + 1) % NV;
//if (curve[prevv].Distance(curve[curv]) < 0.0001 ||
// curve[nextv].Distance(curve[curv]) < 0.0001)
// f3.DebugUtil.Log("DEGENERATE!!");
double angle = curve.OpeningAngleDeg(curv);
if (angle > 179)
{
MeshResult r = mesh.CollapseEdge(loop.Vertices[prevv], loop.Vertices[curv], out cinfo);
mesh.SetVertex(loop.Vertices[prevv], curve[prevv]);
if (r == MeshResult.Ok)
{
goto done_this_iter;
}
else
{
f3.DebugUtil.Log("collinear collapse failed!");
}
}
}
f3.DebugUtil.Log("Did not find collinear vert...");
int i_shortest = -1; double shortest_len = double.MaxValue;
for (int k = 1; k <= NV; ++k)
{
int prevv = k - 1;
int curv = k % NV;
int nextv = (k + 1) % NV;
Vector3d pc = curve[curv] - curve[prevv];
Vector3d pn = curve[nextv] - curve[curv];
double len_sum = pc.Length + pn.Length;
if (len_sum < shortest_len)
{
i_shortest = curv;
shortest_len = len_sum;
}
}
if (i_shortest != -1)
{
int curv = i_shortest;
int prevv = (curv == 0) ? NV - 1 : curv - 1;
int nextv = (curv + 1) % NV;
Vector3d pc = curve[curv] - curve[prevv];
Vector3d pn = curve[nextv] - curve[curv];
int iWhich = (pc.Length < pn.Length) ? prevv : nextv;
MeshResult r = mesh.CollapseEdge(loop.Vertices[iWhich], loop.Vertices[curv], out cinfo);
if (r == MeshResult.Ok)
{
goto done_this_iter;
}
else
{
f3.DebugUtil.Log("shortest failed!");
}
}
f3.DebugUtil.Log("Did not find shortest vert...");
// if we didn't find a vert to remove yet, just arbitrarily remove first one
int v0 = loop.Vertices[0], v1 = loop.Vertices[1];
MeshResult result = mesh.CollapseEdge(v1, v0, out cinfo);
done_this_iter:
List <int> new_verts = new List <int>();
for (int k = 0; k < loop.Vertices.Count(); ++k)
{
if (mesh.IsVertex(loop.Vertices[k]))
{
new_verts.Add(loop.Vertices[k]);
}
}
loop = EdgeLoop.FromVertices(mesh, new_verts);
}
return(loop);
}