/// <summary>
/// Combine a list of triangles into a list of convex polygons.
///
/// Note: This only works on triangles.
/// </summary>
///<param name="triangles">The triangles.</param>
///<param name="maxPolys">The maximun number of polygons to return.</param>
///<param name="tolerance">The tolerance</param>
public static List <Vertices> PolygonizeTriangles(List <Vertices> triangles, int maxPolys = int.MaxValue, float tolerance = 0.001f)
{
if (triangles.Count <= 0)
{
return(triangles);
}
List <Vertices> polys = new List <Vertices>();
bool[] covered = new bool[triangles.Count];
for (int i = 0; i < triangles.Count; ++i)
{
covered[i] = false;
//Check here for degenerate triangles
Vertices triangle = triangles[i];
Vector2 a = triangle[0];
Vector2 b = triangle[1];
Vector2 c = triangle[2];
if ((a.X == b.X && a.Y == b.Y) || (b.X == c.X && b.Y == c.Y) || (a.X == c.X && a.Y == c.Y))
{
covered[i] = true;
}
}
int polyIndex = 0;
bool notDone = true;
while (notDone)
{
int currTri = -1;
for (int i = 0; i < triangles.Count; ++i)
{
if (covered[i])
{
continue;
}
currTri = i;
break;
}
if (currTri == -1)
{
notDone = false;
}
else
{
Vertices poly = new Vertices(3);
for (int i = 0; i < 3; i++)
{
poly.Add(triangles[currTri][i]);
}
covered[currTri] = true;
int index = 0;
for (int i = 0; i < 2 * triangles.Count; ++i, ++index)
{
while (index >= triangles.Count)
{
index -= triangles.Count;
}
if (covered[index])
{
continue;
}
Vertices newP = AddTriangle(triangles[index], poly);
if (newP == null)
{
continue; // is this right
}
if (newP.Count > Settings.MaxPolygonVertices)
{
continue;
}
if (newP.IsConvex())
{
//Or should it be IsUsable? Maybe re-write IsConvex to apply the angle threshold from Box2d
poly = new Vertices(newP);
covered[index] = true;
}
}
//We have a maximum of polygons that we need to keep under.
if (polyIndex < maxPolys)
{
SimplifyTools.MergeParallelEdges(poly, tolerance);
//If identical points are present, a triangle gets
//borked by the MergeParallelEdges function, hence
//the vertex number check
if (poly.Count >= 3)
{
polys.Add(new Vertices(poly));
}
else
{
Debug.WriteLine("Skipping corrupt poly.");
}
}
if (poly.Count >= 3)
{
polyIndex++; //Must be outside (polyIndex < polysLength) test
}
}
}
//TODO: Add sanity check
//Remove empty vertice collections
for (int i = polys.Count - 1; i >= 0; i--)
{
if (polys[i].Count == 0)
{
polys.RemoveAt(i);
}
}
return(polys);
}
