Rendering checks

After a resize or rotation the picture stretches, blurs or leaves a blank strip.

Fans spin and frames drop on Retina screens while normal screens stay smooth.

Come back from a background tab and the animation jumps; every recording comes out different.

Striped flicker where two faces overlap, worse when the camera moves.

Translucent objects swap front and back or vanish at some angles.

Zooming or scrolling to some point slices a chunk off the model.