Saving renders for compositing

It’s a good idea to sep­a­rate the dif­fer­ent steps of a pipeline for com­plex projects, but even in small­er jobs you don’t want to re-ren­der every­time you open Blender.

First dis­able the com­pos­i­tor (ir you’ve been adding nodes already). Then save the ren­der result as an OpenEXR Multilayered file. This will save all your pass­es and ren­der lay­ers. Render lay­ers will be stored as lay­er groups and pass­es as lay­ers inside that group (you get a drop­down in the compositor).

OpenEXR is an open image for­mat devel­oped by Industrial Light & Magic. It sup­ports loss­less encod­ing and up to 32-bit float­ing-point depth and is sup­port­ed by many 3D appli­ca­tions and 2D edi­tors, like GIMP or Krita. You can also use OpenEXR files saved by oth­er appli­ca­tions like Maya in Blender.

All you have to do now is replace the Render Layers input node with an Image node, and select your exr file. I rec­om­mend you do this on a dif­fer­ent blend file if you’re work­ing on a com­plex scene or just plain heavy file to save RAM. Be care­ful with large images in the com­pos­i­tor though, it can quick­ly gob­ble up lots of ram and when you run out of RAM Blender will crash.