New cube2 demo coming

[Bill E]

I think it's amazingly impressive, but that's just me. I'm running it, will check it in soon. It differs from the current cube in that nothing is pre-computed, it's all done in real time.

It lets you rotate a cube using the lightpen, same way the cube demo does by itself. So why impressive? 

The cube's orientation is a 3×3 rotation matrix, updated incrementally on each 

drag step using the small-angle sin/cos approximation to apply a rotational

transform to the cube's vertices to compute new screen positions.

The matrix defines vector coordinates the Type 340 then uses to draw the sides.
Impressive that a PDP-1 can do this with cycles to spare.

Of course, the Type 340 offloads all the display drawing, freeing up all those cycles for the math calculations.

This would have run exactly the same way on a real PDP-1 with a Type 340 display, it's a valid example of 60's era graphics capability.

Bill