Creating "blended" multimatte elements from Vray Blend materials

[freedomfries]

First of all, a huge Bravo to the Chaos Group people for their recent award. It's well deserved in my opinion and I'm very happy you got it!

Alright, I have this vray blend material assigned to a polygon plane. The base layer is a vray mtl with a road texture, and the first coat layer is a sand texture blending into the side of the road. The blend between the two is a simple texture alpha. So I'd like the two materials to pass on multimatte information to produce a multimatte element that has the blend taken into account, to use in Nuke.

Assigning material id's to the base and coat shader produces a black multimatte element when the blend shader is assigned. When the base or coat material is assigned, the multimatte renders a color, so I know it's a problem with my blend material. The only option I found is to create an extra texture element to render that matte used in my blend material.

I wish there was a way to pass through the material ID for the blend material to render a multimatte. Is that possible? More precisely, it seems the multimatte pass is TRYING to render that, but the matte is interpreted as a solid transition, rather than a soft blend between colors. it cannot interpret the value changes in the alpha mask for the vray blend MTL

Thank you!

[Morbid Angel]

Yeah as of today there is no way to pass multimatte between two materials through a blend material. The only way is to create a layered texture where one color is red one color is green for example and use your texture masks there to blend them and pipe that into vray extra tex (as you have figured it out already).

Its an extra step, but I don't know of any better work around at the moment.