[Fluxus] Postprocessing in fluxus

[Johann Korndoerfer]

 Hi

 Thanks gabor, this works fine. Although i get only 48 FPS, which seems 
 quite low for a simple scene like this and i usually get much higher 
 framerates with more complicated fullscreen shaders and rendering to 
 framebuffer objects in OpenGL.
 It seems that even (build-pixels 1 1 #t) limits the framerate to about 
 48 FPS on my laptop with nothing else going on. Quite mysterious.


 Since postprocessing is (or should be) a common task and since even 
 without any actual geometry as input nice things can be done on a 
 fullscreen quad by a shader (raymarching etc.), we might want to 
 integrate this as a feature into fluxus.

 Maybe a simple wrapper like

 (every-frame
   (with-postprocessing (shader-code f)
     (draw-cube))

 would be nice. maybe we could even nest those to obtain multiple 
 passes? So we don't have to bother with planes, vertex shader, screen 
 resolution, and camera transformations when we just want every pixel 
 touched by a fragment shader once.

 Concerning the power-of-two-issue, probably the best method would be to 
 check for GL_ARB_texture_non_power_of_two to be present - only if it is 
 not, round up to the next POT.

 Kas, thanks for the thoughts. I feel that preparing code hurts the 
 performance, even for simple shaders.

 cheers,
 Johann