private fun create_mvp_matrix: Matrix
	do
		var near = -light.depth/2.0
		var far = light.depth/2.0

		var view = new Matrix.identity(4)
		view.translate(-position.x, -position.y, -position.z)
		view = view * rotation_matrix
		var projection = new Matrix.orthogonal(-light.width/2.0, light.width/2.0,
		                                       -light.height/2.0, light.height/2.0,
		                                       near, far)
		return view * projection
	end