rolf_benz_vero.VRay_BumpNormals.png - this pass helps us to define bumps in the texture in order to create more accurate bumps on an object. I have never used that pass, so let's move on to the next one.
rolf_benz_vero.VRay_Caustics.png - This pass represents perfect
caustics, water/glass/metal breaking reflection in the scene and to get this effect working we need to activate Caustics in our scene. For
example, light reflections coming from the
swimming pool from the water create water shapes on the walls or ceiling.
Examples of caustics can be seen here
rolf_benz_vero.VRay_DiffuseFilter.png - pass
that represents the basic colors or pure texture of the models without any lights and shadows. We will use it as the base layer for our
composition.
P r e f e r r e d b l e n d i n g m o d e f o r u s e : Soft light / Screen + adjust layer opacity
rolf_benz_vero.VRay_ExtraTex.png - as you can
see this pass wasn't defined as well as the
others. It's used for adding or isolating specific
textures. We can use it to change the textures
of particular objects and this could be handy
sometimes but I have never used this pass.