Progressive render noise vs time?

[dean_dmoo]

Hi,

Did a search but couldn't find an answer so here's the question;

I want to set up a few renders tonight with noise at 0.005 and rendertime at 2 hours. Now I know a number of the shots don't need 2 hours to clean up to 0.005 (some only need 30min, others 1,5h). Will the progressive render finish early if the noise threshold is reached earlier than the 2 hour time limit?

Thanks!

Dean

[yavor.rubenov]

Hello,

Yes the progressive render will finish when any of the criteria you've set becomes true - if noise is under 0.005 in the image - it will stop rendering even if it only took 30 minutes. For more complicated renders that don't go below 0.005 for 2 hours - the time limit will stop the rendering.

Best regards,
Yavor

[dean_dmoo]

That's great, thanks!

[anthonyh]

hi,
just bumping up this thread for a quick question.
progressive is supposed to stop when 1 of the criteria is met ? (eg. noise/time/subdivs)
however i`m setting my noise threshold (0.02) and according to the vray message window the condition is met and yet it doesn`t stop right away it keeps rendering for several hundred more passes.?
thanks
anthonyh

[yavor.rubenov]

Hello,

Initially V-Ray starts with a higher noise threshold and progressively decreases it so that noise is more uniformly distributed in the initial stages. The message you see is that V-Ray has decreased the noise threshold to the one you've set (0.02). That happens when the noise in about 30% of the pixels is above that threshold and they need more sampling - that's why it keeps rendering more passes.

Best regards,
Yavor

[dsolod]

Hi Yavor,
In my case for one project it goes for hours.
Is it the same explanation here about 30% of pixels above threshold?
Thanks
Dmitry

[werticus]

I've had that issue, it looks like it just gets stuck recalculating the denoiser over and over again, the image itself does not seem to update or even get a denoise result.

I think i fixed it by setting the denoiser to only fire 1 time. Under denoiser advanced, progressive update frequency = 0

[vlado]

Hm, I've never seen that, but it sounds like a bug. Is there a way for us to reproduce this somehow?

Best regards,
Vlado

[dsolod]

Thanks, WerT
I will try to use your suggestion.
Vlado, I will pay more attention to denoiser's behaviour on that particular scene and let you know if it is reproducible.
Dmitry

[JezUK]

Hi guys,

I'm surprised that this is still an issue even in VRay NEXT - as I've seen this denoiser repeat phenomena occurring pretty much all the time and have just accepted it until now, because I have an animation and this will effectively double my render times if not sorted out.

werticus, there is no "Progressive Update Frequency" under Denoiser Advanced

Is no one else getting this error ?

[yavor.rubenov]

The setting for update frequency is in Render Setup->Settings->Post Effects rate. If you set it to 0 the denoiser will update only when the render finishes.

As for the issue with the stuck denoiser itself - we still haven't got a way to reproduce it here. If it happens to you in this scene - could you share it with our support so we can fix it ?

[JezUK]

Hi Yavor,

Mine was set to 10, yet as you can see, there are more than 10 Recalculating Denoiser cycles (I think it's 36 or 37 there).

I set that Post Effect Rate to 0 like you said and it seems that the render is still getting to the 5 minutes (time limit I specified) even though the Final Noise Threshold (0.03) was reached after just 2.5 minutes.....

I've tried one other test - no RE at all (so, no denoiser in the scene) - Final Noise Threshold (0.03) reached at 2.25mins, 'rendering' continued to 4.5mins.......

Those extra 2.25 mins per frame will add an extra 30 hours to my total animation render time.......so this needs to be sorted

This is a scene I have just purchased from Turbosquid (so I cannot give it to you) and I got the usual message when I opened it, i.e. saying that it was produced on an older version of VRay and did I want to convert it to use the newer features etc etc (to which I answered Yes. I will try creating a new fresh scene and just importing the geometry and starting with new cameras and lights and VRay settings.

[JezUK]

Okay, some interesting results.....

Reset scene and just merged geometry into an empty scene.

Used a new VRay Sun and a new VRay Physical Camera (the old type) and so I would expect slightly different results as their positions aren't exactly the same....

NO Render Elements, Noise Threshold reached in 4m30s, carried on rendering to 5m01s (so it is continuing as far as I'm concerned, even when the Noise Thres is reached).

Add a Denoiser RE (set to default), Post Effect Rate = 0 - Noise Threshold reached in same 4.5 mins (of course !), carrried on rendering to 5 mins.......

I tried one more test...... Post Effect Rate = 10, and Render Time to 10 minutes - again, Noise Threshold reaced in 4.5mins, carried on rendering until 7.5mins and here is the V-Ray Messages;

Notice it did 16 "Recalculating denoiser" cycles (when PER was set to 10).

[yavor.rubenov]

As I've explained a few posts above - the message "Final noise threshold set: <your threshold>" doesn't mean that the sampling is done. V-Ray first starts with much higher noise threshold and progressively lowers it - you see messages like "Noise threshold lowered to 0.030303 with 54.1 percent active pixels". This means that 54.1% of the pixels are noisier than 0.030303. When the active pixels go below roughly 30% V-Ray will lower the noise threshold again till it reaches the noise you've specified - at that point there might still be many active pixels. V-Ray will output the message "Final noise threshold set" and will sample those active pixels. Depending on the scene it might take minutes till all those pixels reach noise level below the one you've specified. While this is going on there are no more messages "Noise threshold lowered to..." so you only see the messages about the denoiser but this doesn't mean V-Ray is only denoising.

As for the Post Effect Rate - it is a rate parameter not a fixed number. In the mouse hint message there are details about it but generally the idea is that bigger Post effect rates will cause the post effects (denoiser, lens effects) to be calculated more often.

[JezUK]

Thanks Yavor for your great explanation which I really appreciate, I now understand what is going on

I will have a further play