I am trying to obtain a p-map (position map) in 2.80. Since the only way I found is to have a different material with a Geometry/Position node as input, I need to switch between materials (the "real material" and the p-map material). Since I would like to render them in the same rendering (it is part of an animation and I need both images for each frame), I was looking for a trick. The first trick I found is to use a material override in a new scene. But Blender 2.80 does not (yet?) have a material override (doh!). So I tried to do the following: I created a new scene (SceneForPMap) and I set a new material, in that scene for all the objects, hoping that the object material is a per-scene setting. Then, I added a new RenderLayer input in the compositor and put its output in a FileOutput node.
But I found a set of very hard-to-understand problems:
- There is a compositor configuration for each scene... I would expect to have a compositor per Blender file, since it can have as input a render of a scene (the compositor seems to be more "high-level" than a scene).
- The material is not per-scene, if I change the material of an object (with a scene selected in the top drop-down select box), it is the same in all the scenes (changing the scene in the top drop-down select box)... but more confusing, if I render (F12) I obtain a material for the normal scene RenderLayer and the p-map material for the RenderLayer of SceneForPMap.
I am confused, maybe I am doing something wrong, or I misunderstood something else.