public static Vector2 Project(Vector3d vector)
{
// Add w element for conversion
Vector4d v4 = new Vector4d(vector);
v4.W = 1.0;
// Get conversion matrices
Matrix4d modelView;
GL.GetDouble(GetPName.ModelviewMatrix, out modelView);
Matrix4d projection;
GL.GetDouble(GetPName.ProjectionMatrix, out projection);
int[] vp = new int[4];
GL.GetInteger(GetPName.Viewport, vp);
Matrix4 viewport = Matrix4.Identity;
// NOTE: Matrix4 type assumes the result obtained by "vector * matrix", instead of "matrix * vector".
viewport.Row0.X = vp[2] / 2;
viewport.Row1.Y = -vp[3] / 2;
viewport.Row3.X = vp[2] / 2;
viewport.Row3.Y = vp[3] / 2;
// Convert to window coordinate system
v4 = Vector4d.Transform(v4, modelView);
v4 = Vector4d.Transform(v4, projection);
v4 = Vector4d.Multiply(v4, 1.0 / v4.W); // Manual normalization required
v4 = (Vector4d)Vector4.Transform((Vector4)v4, viewport);
// Return only x and y
return(new Vector2((int)v4.X, (int)v4.Y));
}