public static void Clear()
{
_worldMatrixStack.Clear();
_worldMatrix = Matrix4.Identity;
_worldMatrixChanged = true;
_clipStack.Clear();
ClearScreenClip();
GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit | ClearBufferMask.StencilBufferBit);
}