Optimize render time for Vray Fur on moving object

[Mathieu_1980]

Hi everybody,

I'm quite rookie in rendering Fur and I'm wondering what is wrong with my render preset !
My render time is so long and maybe it's the price to pay for high quality image, maybe I did something stupid or wrong, or wrong and stupid...

My scene is a moving character with Fur, 3 Vray lights and a plane for the ground. No HDRI, just a black color as environnemnt.

- My main problem was to avoid the noise in the shadows and in of the dark parts of the fur. For that I strongly increased the subdivions of the image sampler. Result is good with Min Subdivs : 64 (Max subdivs unchecked) this seems so crazy to me because normally I rarely exceed >Min Subdivs : 1 and Max subdivs : 12. But with my actual scene, it's too noisy before Min Subdivs 50.

- For GI, I'm using Brutal force as primary, and Light Cache (Subdivs : 2000) as secondary engine.

- I also use Vray SphereFade to render only the character zone.

I did not change anything else from the basic render presets.

I'm rendering 1920x1080px using Rebus farm, and with this preset my render time per frame is around 60 minutes with Rebus Farm render !

What would be smart to change to have faster render, maintaining the good quality render and not noisy Fur ?
Or is it the normal render time for rendering Fur for production ?

In advance, thanks so much for your help !

Mathieu

[Svetlozar Draganov]

It's true that hair and fur objects might require a little bit of extra time in order to be rendered without noise or flickering in the animation but Min.Subdivs set to 64 sounds quite a lot.
It's interesting to have a look at the scene as well as some render outputs so I could have a better picture for the quality, render times and scene settings.
Would it be possible to send us a few frames of the animation with their render times and the actual scene for inspection?

Looking forward to hearing from you.

[Mathieu_1980]

Hello, thanks for your help ! Where can send you the files ? I can't post it here cause this project is pretty touchy with confidentiality... and i'm sorry for this...

[Svetlozar Draganov]

You can send the project to support@chaosgroup.com, please include me in CC (svetlozar.draganov@chaosgroup.com) and include a link to this thread for reference.

[Mathieu_1980]

Thank you so much, i've just send you an email with the project and the final render...

Best regards,
Mathieu

[Svetlozar Draganov]

Thank, I checked the scene and here is what you can do in order to optimize render times and quality.
Using only Min.Samples for the Image Sampler disables any Sampler optimizations and due to that the render times grows exponentially.
V-Ray doesn't need that much Subdivisions for each pixel, yes for some regions 32 subdivs might be fine to clear the noise but in most of the image such higher number is not needed.
It's much better to use Min and Max Subdivs values like 1 and 32 and then to control the balance between them with Noise Threshold parameter. I run a quick test with 1/32/0.01 and I got pretty stable result, I'm pretty sure the result will be good enough even with 1/24/0.01.

Another option to clear the finest noise in animations is V-Ray Denoiser. This approach will allow you to render a animation with a little bit of noise and then you can get rid of that noise using V-Ray Denoiser. If you haven't tried it yet I recommend to try it out.

I will send you the result from my tests via email.

More information about Image Sampler parameters could be found here:
https://docs.chaosgroup.com/display/...+Image+Sampler

[Mathieu_1980]

Oh thank you so much, it really helps me !

It confirms the basic presets are very clever and very usefull in different kind of rendering.
I will find out more about the Denoiser, never tried it but it seems perfect in my case.

Thanks again !

[Svetlozar Draganov]

As a new user my recommendation is to stick with the default values and to only change them if they doesn't meet your expectations in terms of quality or render time.
Otherwise you may accidentally set up parameters that increase render time dramatically without much change in the quality.