Need advice on certain geometry rendering longer than others.

[evanmichalski]

SPECS:

Geforce GTX 780ti

Asus Sabertooth x79

Intel i7 4930k oc'd @3900mghz

Windows 8.1 x64 w/ latest updates

3ds max 2014

 

 

V-ray 2.50.01SETTINGS

http://i.imgur.com/1ExSpsJ.jpg

MATERIAL IN QUESTION

http://i.imgur.com/yvAD2cB.jpg

Camera/Lights/Environment

http://i.imgur.com/8T0kpSo.jpg

SampleRateInfo

http://i.imgur.com/kPzDZDC.jpg

 

Long story short: 14 hours into a rendered scene with huge amounts of geometry and because I'm on a xmas deadline, I'm gonna to let the render finish plus I'd rather have something to show than nothing at all. Needless to say the geometry in question that I need addressing:

 

1. It's a feather I created with ct-feather-generator

2. I made 4 with at least 800 strands each @ 147,000 faces (I know... a lot)

3. Mat is a VrayHairMtl

 

Once it's on the final rendering stage, each bucket processing parts of the feather are taking like 30-40 minutes each, so doing the math it's be another 16 hours to finish. Additionally, during the building light cache phase, that also took 4 hours to finish before moving to the next pass. I think I have an idea what it may be but like I said, I could use some help expediting this process before Monday. With that said could it be:

 

1. The reflect/specularity is too high?

2. The displacement map playing havoc with my rendering?

3. Should I have made my feathers a proxy? Would that even help?

4. I followed Grant Warwick's advanced tweaking and subdvisions are @90. SamplerateInfo appears to be fine as there's not AA being used. But again, I'm only speculating here, so could I tweak the DMC sampler some more, and conversely the mat subdivisions?

 

This is by no means my final render so I'm well aware of the noise issue and I had also planned to re-render this at a 4k resolution. But since I'm looking maybe a 33 hour render here at 1080p, I'm leery to re-render it at a higher resolution. Everything else in my scene rendered fairly quickly, where each bucket only needed 10-30 seconds for to complete. But when it reaches those damn feathers, the bucket time exponentially increases to 30-40 minutes each! Anyways, it's 2am here now so I'm hitting the sack. I'll be checking back here around noonish mountain time. Thanks in advance for your responses.

 

Update 1: Ok, just a follow-up, I think I may have solved it on my own. The barbs from the feather had push modifier on them with a radius of .21cm, so I guess the extra thickness of the strands with the combination of the VrayHairMtl is what is causing the increased render time. I'll post back with my results.

 

Update 2: Yea, that was the culprit. The strands were too thick thereby creating more calculations for the vray fur shader. For future reference though if anyone knows, what kind of optimizations I can do to speed up render times without sacrificing the quality? I'll be googling in the meantime.

Edited December 28, 2014 by evanmichalski

[Devin Johnston]

Anytime I've used the Vray Hair material I've always had very long render times, my best advice would be to find a way to create the look without using it if times an issue.