Hm, you are talking about two different things here. One is a bump-preserving AO pass, and the other is VRayDirt working inside a bump slot. Which one do you mean?
I suppose I was just being lazy and putting 2 wishes in one thread. It would be nice it both wishes were possible.
VrayDirt in bump slot
My current workflow is to use invert normals with VrayDirt to generate masks. Then I unwrap and render to texture and generate a bump map. This is fine but if it were possible to have the VrayDirt work in the bump of a material or even the VrayDisplacement modifier this would be useful.
bump-preserving AO pass
The bump-preserving AO pass adds a subtle level of detail. I know that it is possible to set this up by hand (or maxscript) within Vray but Brazil has a really easy workflow for it and if its possible in Vray I can see no reason not to have it.
IF it should be possible to use VRayDirt as a bump map, do you think it would allow a rounded corner effect like the (pantented and thus “forbidden to copy”) way mental ray does it? One of the drawbacks of VRay’s EdgesTex is that it only works on welded edges, whereas mental ray allows even unwelded edges to be rounded. And since a lot of CAD-data imported into 3dsmax has separate, unwelded surfaces (although their edges line up perfectly and appear closed) this would help a lot!
I’ve tested it by adding a VRayDirt map with inverted normals onto one of those imported models, and I get a perfectly nice, soft line long those unwelded edges, while the EdgesTex doesn’t see these open edges as “corners”.
Bringing this back up I am again working on a project with CAD data that has a lot of unwelded edges. Would it be possible to make the EdgesTex (in the bump slot) work with unwelded edges as well?
You can make this work by applying the ProOptimizer modifier. Make sure to set it to weld vertices with 0 distance, protect normals on. That way, all the normals and the surface shading should stay intact. Afterwards it should work as expected. At least that is the method I use on car head- and taillights etc… Be aware that selecting elements on these objects is all messed up afterwards, Max will select all elements at once instead of single patches.