VrayBlendMtl performance

[gimiky]

does the vrayblendmtl slow down linearly\exponentially with the addition of more coating materials? obviously as things get more complex i would expect them to slow down, but can someone roughly quantify it?

i have a vrayblendmtl with 4 coat materials (2 of them are very simple, no tracing, 2 have glossy reflections) and sampling time has gone through the roof.. i didn't notice until i went to final quality, as test rendering with adaptive DMC and a higher noise threshold didn't give me any trouble. (rendertimes were 45 min for a single vraymtl with comparable glossiness\reflection, now they're 2+ hours with the blend)

any input is greatly appreciated.. thanks,
greg

[joconnell]

I've found that the unified sampling can bite you in the ass in certain cases - I was doing some car renders before christmas without the time top do proper render optimisations so render times were fairly high - after the holiday I revisited it and halved them. I've found there's no solid rule about what works, you do need to do some experimentation to get the4 best speed / quality payoff. Can you post a frame here and your render settings?

[vlado]

It depends on how you have set up your material, but if it has a lot of reflective coats, V-Ray has to trace that many additional reflective rays for the material. This can increase the number of traced rays by quite a lot.

Best regards,
Vlado