Minecraft wiki entry for Shaders, associated text: Here's the process of how a post-processing shader is used in game: first, the shader initializes all of the render targets specified in the "targets" list with the proper width and height. After that, the shader goes through each render pass specified in the "passes" list from first in the list to last in the list. Each pass will apply the program shader on the render target specified by "intarget" (with any extra data provided by other auxiliary render targets) and output the end result on the render target specified by "outtarget".