Hi,
Is it possible in 3ds max to render the VRayCar paint material in separate passes for compositing?
Thanks
N
It is not possible out of the box but it can be done with separate VrayCarPaintMtl plugged into VrayBlendMtl and then extracted via VrayMtlSelect Render Element.
Separate VrayCarPaintMtl are needed for each pass - one for Base Layer another one for Flake Layer and one more for Coat Layer.
I’ll prepare sample scene and I’ll post it afterwards.
Here is the setup:
1.First a separate VrayCarPaintMtls should be created for each VrayCarPaintMtl component - Base/Flakes/Coat.
(Flakes component could be also simulated with VrayFlakesMtl also)
2.Then plug all those materials into VrayBlendMtl.
3.Create MaterialSelect Render Elements for each pass - Base/Flakes/Coat.
4.Then combine the result from those layers in Nuke to reconstruct the final appearance.
5.Then you can tweak each component separately. In the example bellow I made the Base color from blue to red, Flakes from blue to green and I have increased the strength of the Coat layer.
Scene+Render Elements+Nuke Comp
Notes:
1.Base + Flakes components must be blended with Additive(shellac) mode OFF while Coat must be mixed with Additive ON.
(The Coat component could be also mixed without Additive mode, please check Vlados post bellow)
2.Base Layer requires additional setup in order to match perfectly original VrayCarPaintMtl:
3.Flakes material cannot be extracted separately with VrayMaterialSelect render element. This is not an issue since it is possible to extract Base+Flakes and Base only - then the Difference between those two passes is exactly the Flakes pass.
Thank you!
I would actually use the VRayFlakesMtl material for the flakes layer rather than a full-blown car paint mtl. Then you won’t need the additive mode (which in general it is good to avoid).
Best regards,
Vlado
This is what I actually used in the attached example - the Base and the Flakes(VrayFlakesMtl) are blended in non-additive mode but there is no way to add the Coat layer properly without additive mode.
I didn’t know that it is possible to simulate Shellac effect that way - thanks for letting me know 
Very informative. Thanks for posting the example and the trick to avoid the additive mode.
You can also just render another pass with the car shader material applied with a black base coat and black diffuse so you get only the flakes in this layer. Then comp it on top of your original render. And you could use RPManager to setup your passes in this case you would use the RPM material to be switched between passes.