Crude Background Subtract

This is based on the Jitter patch ‘crude example of background elimination’,
originally by Josh Kit Clayton, posted by Andrew Benson here:
cycling74.com/forums/topic/phot … nce-matte/

I’m new-new to Touch so I’d love any feedback on design patterns / best practices etc.

Also new-new to GL so do let me know if any of these shaders are wonky.

The ‘slide’ implementation is from Jitter as well.