Untitled

                public Vector2 GetMouseGridPosition() {
                        Vector3 near = new Vector3(new Vector2(lastpos.X, lastpos.Y), 0);
                        Vector3 far = new Vector3(new Vector2(lastpos.X, lastpos.Y), 1);

                        Viewport viewport = new Viewport(0, 0, graphics.PreferredBackBufferWidth, graphics.PreferredBackBufferHeight);
                        near = viewport.Unproject(near, camera.Projection, camera.View, camera.World);
                        far = viewport.Unproject(far, camera.Projection, camera.View, camera.World);

                        Vector3 nrm = Vector3.Normalize(far - near);
                        Vector3 x = near - nrm * (near.Y / nrm.Y);
                        return new Vector2(x.X, x.Z);
                }