// Triangulate the polygon.
//
// For a nice, detailed explanation of this method,
// see Ian Garton's Web page:
// http://www-cgrl.cs.mcgill.ca/~godfried/teaching/cg-projects/97/Ian/cutting_ears.html
static List <int> Triangulate(this PolygonShape p_polygon)
{
List <int> v_indexes = new List <int>();
if (p_polygon.Vertices.Count > 2)
{
// Copy the points into a scratch array.
Vector2[] v_pts = p_polygon.Vertices.ToArray();
// Make a scratch polygon.
MorphableShape v_pgon = new MorphableShape(v_pts);
// Orient the polygon Clockwise
if (!v_pgon.IsOrientedClockwise())
{
v_pgon.ReverseOrientation();
}
// Make room for the triangles.
List <MorphableShape> v_triangles = new List <MorphableShape>();
// While the copy of the polygon has more than
// three points, remove an ear.
while (v_pgon.Vertices.Count > 3)
{
// Remove an ear from the polygon.
v_pgon.RemoveEar(v_triangles);
}
// Copy the last three points into their own triangle.
v_triangles.Add(new MorphableShape(new List <Vector2>()
{
v_pgon.Vertices[0], v_pgon.Vertices[1], v_pgon.Vertices[2]
}));
//Find Index of vertice of each triangle in self Vertice List
foreach (var v_triangle in v_triangles)
{
if (!v_triangle.IsOrientedClockwise())
{
v_triangle.ReverseOrientation();
}
foreach (var v_vertice in v_triangle.Vertices)
{
for (int i = 0; i < p_polygon.Vertices.Count; i++)
{
var v_thisVertice = p_polygon.Vertices[i];
if (v_thisVertice == v_vertice)
{
v_indexes.Add(i);
}
}
}
}
}
return(v_indexes);
}
// Return true if the three points form an ear.
public bool FormsEar(int p_a, int p_b, int p_c)
{
if (Vertices != null)
{
// See if the angle ABC is concave.
if (GetAngle(Vertices[p_a], Vertices[p_b], Vertices[p_c]) > 0)
{
// This is a concave corner so the triangle
// cannot be an ear.
return(false);
}
// Make the triangle A, B, C.
MorphableShape v_triangle = new MorphableShape(new List <Vector2>()
{
Vertices[p_a], Vertices[p_b], Vertices[p_c]
});
// Check the other points to see
// if they lie in triangle A, B, C.
for (int i = 0; i < Vertices.Count; i++)
{
if ((i != p_a) && (i != p_b) && (i != p_c))
{
if (v_triangle.PointInShape(Vertices[i]))
{
// This point is in the triangle
// do this is not an ear.
return(false);
}
}
}
// This is an ear.
return(true);
}
return(false);
}