// Update triangle connections and edge error after a edge is collapsed
void update_triangles(int i0, MSVertex v, List <int> deleted, ref int deleted_triangles)
{
Vector3 p = Vector3.Zero;
for (int k = 0; k < v.tcount; k++)
{
var r = refs[v.tstart + k];
var t = triangles[r.tid];
if (t.deleted)
{
continue;
}
if (k < deleted.Count && deleted[k] > 0)
{
t.deleted = true;
deleted_triangles++;
continue;
}
t.v[r.tvertex] = i0;
t.dirty = true;
t.err[0] = calculate_error(t.v[0], t.v[1], ref p);
t.err[1] = calculate_error(t.v[1], t.v[2], ref p);
t.err[2] = calculate_error(t.v[2], t.v[0], ref p);
t.err[3] = Math.Min(t.err[0], Math.Min(t.err[1], t.err[2]));
refs.Add(r);
}
}
// Check if a triangle flips when this edge is removed
bool flipped(Vector3 p, int i0, int i1, MSVertex v0, MSVertex v1, List <int> deleted)
{
int bordercount = 0;
for (int k = 0; k < v0.tcount; k++)
{
var t = triangles[refs[v0.tstart + k].tid];
if (t.deleted)
{
continue;
}
int s = refs[v0.tstart + k].tvertex;
int id1 = t.v[(s + 1) % 3];
int id2 = t.v[(s + 2) % 3];
if (id1 == i1 || id2 == i1) // delete ?
{
bordercount++;
deleted[k] = 1;
continue;
}
Vector3 d1 = vertices[id1].p - p; d1.Normalize();
Vector3 d2 = vertices[id2].p - p; d2.Normalize();
if (Math.Abs(Vector3.Dot(d1, d2)) > 0.999)
{
return(true);
}
Vector3 n;
n = Vector3.Cross(d1, d2);
n.Normalize();
deleted[k] = 0;
if (Vector3.Dot(n, t.n) < 0.2)
{
return(true);
}
}
return(false);
}