"reflection level" output in VRay Mtrl?

[mts]

Hey there,
I am currently trying to create a car paint shader by creating my own shader network using a glossy base material and a reflective coating.
Using the VRay Blend Material seems to be the proper choice for me but my problem is that I cannot find a way to mask the base layer by the reflection level of the clear coating layer to get physically correct results (where the clear coating is 100% reflective I do not want to see anything of the base layer at all and where it is 0% reflective because of fresnel I want to see the base layer as if it would be all on its own).

With Mental Ray's mia_material_x I would simply use the inverted reflection_level output as a mask for the base layer but in VRay I am missing a feature like this.

Anybody can help? The Vray Material's "reflectionColorAmount" looks promising to me but it neither works as a color map nor can I find any more info about it.

Any help is appreciated, thanks.

[vlado]

It's quite simple actually. You would normally put a VRayFresnel texture as the blend amount for the coat layer in the VRayBlendMtl material. That's all - there is no need to modify either the coat or the base materials; the blend material will automatically do the necessary math.

This is of course, provided that it is not in "Additive mode". If it is, things are more complicated; in general I would not recommend turning the additive mode on.

Best regards,
Vlado

[mts]

that's quite simple indeed. thanks!

[irwit]

Ahh, so the gloss coat would naturally darken the base coat as it would mask it.

I've being going the same route as mts making things more complicated than they needed to be. Thanks for the good advice!