glasses/sunglasses/goggles with mirror effect

[Mats_O]

Hi all,

I am rendering glasses/sunglasses with mirror-lenses. The lenses could be for example red glass with yellow mirror, grey glass w silver mirror, green glass with red mirror etc. I am building a library with base materials and mirror materials to be able to combine those as i want later.

I get quite good results with the VRayBlendMtl. However something is missing. The blend material is more of a mix between the base material and the mirror material, and if the the mirror for example is 90%, the base material almost has no effect which is not true in real life, I beleive in this particular case. Imagine a very opaque base material with a transparent but very reflective mirror material. If I make the mirror material contribute with 90% the final material is very transparent sincer the base material is almost gone. In the real world the opaque base material would still block most of the light from passing through eventhough there is a mirror shellac on top of it.

I imagine I miss something, such as shellac mode, Energy Preservation option or...? You have any ideas?

Thanks in advance!

[Morbid Angel]

vray blend material has an option to be additive, which mimics shellac behavior. You can safely use it, if you don't double up reflections, so for example if your base material does not have any reflection, then it will be more or less correct. Using additive mode though will create possibly some overbrights as well as produce incorrect energy preservation.

[Mats_O]

Thanks, I will give it a try. Exactly what does the shellac mode mean? For examlpe if I apply 100% of a coat material on top of the base material and then if the coat material has a falloff map which is going from black to white for reflection - will the base material show correctly in those areas where the coat material is transparent due to the falloff map? Eventhough the base material is covered 100% with the coat material? That is what I want...

[Morbid Angel]

I guess the best way for you to understand how this works is just do some experiments.
But if you look at the basics, then in any place where there is reflection, the diffuse component is darker. For example if you enable fresnel then at a glancing angle, the diffuse part of the material will become darker, since less light gets there as its occluded by the reflection coat.

If you use additive mode, it will do similar effect as when you do additive in a composite, so instead of darkening your diffuse at a glancing angle it will add to whatever you have there already making it brighter, therefor making it physically incorrect.

The proper way to layer such materials is just use falloff map in fresnel model on your coats as blending map, vray will do the math for you.