Pretty simple fix it would seem. Just swap the negative values so they are positive values. node_stack_bottom = 1.5, 0.0, 0.0, 0.0, 1.0, 0.0, 3 node_stack_top = 1.5, 3.0, 0.0, 0.0, -1.0, 0.0, 3 where it was node_stack_bottom = 1.5, 0.0, 0.0, 0.0, -1.0, 0.0, 3 node_stack_top = 1.5, 3.0, 0.0, 0.0, 1.0, 0.0, 3