private List <Vector2[]> TrianglesFromTessellator(Tess tess)
{
var triangles = new List <Vector2[]>();
// Do the tessellation
tess.Tessellate(WindingRule.EvenOdd, ElementType.Polygons, 3);
// Extract the triangles
int numTriangles = tess.ElementCount;
for (int i = 0; i < numTriangles; i++)
{
var v0 = tess.Vertices[tess.Elements[i * 3 + 0]].Position;
var v1 = tess.Vertices[tess.Elements[i * 3 + 1]].Position;
var v2 = tess.Vertices[tess.Elements[i * 3 + 2]].Position;
var triangle = new List <Vector2>()
{
new Vector2(v0.X, v0.Y),
new Vector2(v1.X, v1.Y),
new Vector2(v2.X, v2.Y),
};
// Assume each triangle needs to be CCW
float cross = GeoMath.Cross(triangle[0], triangle[1], triangle[2]);
if (cross > 0)
{
triangle.Reverse();
}
triangles.Add(triangle.ToArray());
}
return(triangles);
}
public bool CanMergePolygons()
{
// The two polygon partners can be merged if the two vectors on each point where they would merge don't create a concave polygon
// Concave testing is done through a cross product and assumes CCW winding of the polyon points
// Can merge point P of the Major/CCW partner?
{
// A = CWW[P - 1]
// B = CWW[P]
// C = CW[P + 1]
var A = this.MajorPartner.PrevPoint(this.MajorPartner_pIndex);
var B = this.MajorPartner.Points[this.MajorPartner_pIndex];
var C = this.MinorPartner.NextPoint(this.MinorPartner_pIndex);
float cross = GeoMath.Cross(A, B, C);
if (cross > 0)
{
return(false);
}
}
// Can merge point Q of Major/CCW partner?
{
// A = CWW[Q + 1]
// B = CWW[Q]
// C = CW[Q-1]
var A = this.MajorPartner.NextPoint(this.MajorPartner_qIndex);
var B = this.MajorPartner.Points[this.MajorPartner_qIndex];
var C = this.MinorPartner.PrevPoint(this.MinorPartner_qIndex);
float cross = GeoMath.Cross(A, B, C);
if (cross < 0)
{
return(false);
}
}
return(true);
}
