I'm seeing the same thing - as the cube spins different faces are getting rendered in the fore-ground which should be in the background etc. I remember reading up about 3d progamming in the olden days ('95) and they always were talking about depth sorting, and z-buffers, and bsp something-somethings that were used to determine which vertices should be rendered in which order.

I reckon this is what will be covered in the next tutorial (I hope so anyway Smiley