/// <summary>
/// Get a face loop or ring from a set of winged edges.
/// </summary>
/// <param name="wings"></param>
/// <param name="face"></param>
/// <param name="ring"></param>
/// <returns></returns>
static HashSet <Face> GetFaceLoop(List <WingedEdge> wings, Face face, bool ring)
{
HashSet <Face> loop = new HashSet <Face>();
if (face == null)
{
return(loop);
}
WingedEdge start = wings.FirstOrDefault(x => x.face == face);
if (start == null)
{
return(loop);
}
if (ring)
{
start = start.next ?? start.previous;
}
for (int i = 0; i < 2; i++)
{
WingedEdge cur = start;
if (i == 1)
{
if (start.opposite != null && start.opposite.face != null)
{
cur = start.opposite;
}
else
{
break;
}
}
do
{
if (!loop.Add(cur.face))
{
break;
}
if (cur.Count() != 4)
{
break;
}
// count == 4 assures us next.next is valid, but opposite can still be null
cur = cur.next.next.opposite;
}while (cur != null && cur.face != null);
}
return(loop);
}