public static int[] TesselatePolygon(V[] vertices)
{
var count = vertices.Length;
if (count < 3)
{
throw new ArgumentException("Tesselator needs at least 3 vertices");
}
var result = new int[(count - 2) * 3];
var resInd = 0;
var tessVerts = TessVertex.CircularList(count);
foreach (var tv in tessVerts)
{
UpdateVertexAngle(tv, vertices);
}
foreach (var tv in tessVerts)
{
UpdateIsEar(tv, vertices);
}
while (count > 3)
{
var curr = tessVerts.Where(v => v.IsEar).MinItems(v => v.Angle).First();
var prev = curr.Previous;
var next = curr.Next;
result[resInd++] = prev.Index;
result[resInd++] = curr.Index;
result[resInd++] = next.Index;
curr.Delete();
UpdateVertexAngle(prev, vertices);
UpdateVertexAngle(next, vertices);
UpdateIsEar(prev, vertices);
UpdateIsEar(next, vertices);
tessVerts = next;
count--;
}
foreach (var tv in tessVerts)
{
result[resInd++] = tv.Index;
}
return(result);
}
private static void UpdateIsEar(TessVertex current, V[] vertices)
{
if (current.IsReflex)
{
current.IsEar = false;
}
else
{
var prev = current.Previous;
var next = current.Next;
var p0 = vertices[prev.Index].position;
var p1 = vertices[current.Index].position;
var p2 = vertices[next.Index].position;
current.IsEar = current.Where(v => v != current && v != prev && v != next && v.IsReflex)
.All(cv => !PointInTriangle(vertices[cv.Index].position, p0, p1, p2));
}
}
private static void UpdateVertexAngle(TessVertex tessVert, V[] vertices)
{
tessVert.Angle = AngleBetweenEdges(
tessVert.Previous.Index, tessVert.Index, tessVert.Next.Index, vertices);
}
