Pops the framebuffer from the renderers FBO stack and sets that as the active target,
then draws the
source Render Target to it. It then resets the renderer textures.
This should be done when you need to draw the final results of a pipeline to the game
canvas, or the next framebuffer in line on the FBO stack. You should only call this once
onDraw handler and it should be the final thing called. Be careful not to call
this if you need to actually use the pipeline shader, instead of the copy shader. In
those cases, use the
The Render Target to draw from.