Hair color dictates Rendertimes?

[Mokiki]

I'm currently trying to find a good hairsolution for the office and decided to play around with the Ornatrix/hairfarm demos. (Thats why I can't provide any test scene since saving is disabled)
While trying to get a feeling for what I have to not go overboard with rendertimes and still keep quality I noticed that apparently the brighter the hair color gets the longer the rendertimes are which to me is slightly confusing.
For example if I use the vray hair material and switch between blond shiny and red shiny I get vastly different results in renderspeed.

Additionally to hijack my own post are there any known speed differences between Ornatrix and Hairfarm? And do you guys would have any pointers to render hair/fur efficiently balancing quality vs rendertimes. Because it seems that the only really difference I can make in terms of renderspeed/quality besides the haircolor is playing with the AA settings. (While running BF/LC)

[vlado]

Lighter hair color causes the rays to bounce more inside the hair volume when you have GI enabled, which leads to longer render times.

There are no differences in speed between Ornatrix and HairFarm when rendered through VRayOrnatrixMod and VRayHairFarmMod respectively.

About the render speed, it depends. Which V-Ray version are you using?

Best regards,
Vlado

[Mokiki]

Thanks Vlado for the quick response and explanation
I'm using Vray 3

[vlado]

Ok; can you show me some images (or you can email them to vlado@chaosgroup.com)? If the hairs are too thin, it might make sense to make them a bit wider and use transparency instead to make them appear thinner. Other than that, newer builds will have some additional optimizations for hair, both generally and in the BF+LC scenario specifically.

Best regards,
Vlado

[Mokiki]

Thanks for taking the time Vlado. Really appreciate it!

Here are two images I rendered last week. Those images are at 100% scale and took around 3 hours to render on a intel xeon 5680 x2 with BF/LC and I think transmission amount was 0. The tail consisted of around 300k hairs the text of around 1 million. At least those are the things I remember.
At least personally I thought the rendertimes were a bit high. But it probably like you said connected to the thickness of the hair. Mine were really thin to get the look I was going for.

[vlado]

Ok, with such thin hairs it may definitely make more sense to make them thicker but transparent. It is on the "to do" list for V-Ray to do something similar automatically... will see where it goes.

Best regards,
Vlado

[Mokiki]

Thanks Vlado will try that next time