Feature Request: Framebuffer or Last Frame support.

[jgshaban]

This plugin is super useful. Thanks for keeping it maintained!

I was wondering how much trouble it would be to implement some form of framebuffer, or the ability to retrieve the previously used/drawn frame? A few shader development programs I've poked around with have some form of framebuffer (sometimes many), definable 2d textures whose values persist between frames, or a 2d texture constant of the last output frame.

I feel that if this feature were present, it would make some shaders easier to write. For example, motion blur, or persistent afterimages like those in vintage CRT effects would be feasible.