Progressive render stops withour reaching time/noise limit, withour prepasses works fine

[palibebeh]

Hi,

I stumbled upon this issue today. When I render a scene (interior viz) with GI prepasses and progressive renderer for the final pass, the render stops after some random time, not reaching time/noise limit. I set time limit for 10 minutes, but it stops after 3, or even just a few seconds in a different view. Noise level is set to 0,0 or 0,001 but the picture is still very noisy. BUT when I save IRR map to a file and render without prepass using the saved IRR map, the render goes on for the set amount of time without aby problems. This is the first time I had this issue. I have over a dozen renders to complete today and have to manually switch between GI prepass / final render for each one of them.
Has any of you guys ever experienced something similar?

thanks,

Maciej

[radoslav.platikanov]

The time limit currently includes the time of the prepasses, so maybe it's reaching it?

[palibebeh]

Does it? That's weird, because the render ends after some arbitrary time. For example in one frame LC + IRR takes about 10 minutes, final pass cuts after 3-4 minutes. In the next frame LC+IRR also takes about 10 mins but final pass ends after 5 seconds (?).
And while help docs for vray state that the time limit is for final pass only (This is the render time for the final pixels only; it does not include any GI prepasses like light cache, irradiance map, etc.), in some scenes it works like this while in others (like in the example above) it doesn't. Why is that?

[radoslav.platikanov]

It should always include any GI prepasses, it shouldn't depend on the scene. This was changed in 3.50 I think, and we've missed to update the docs (thanks for the pointer).
The exact reason for the render end can be seen in the log, for example: "Progressive rendering finished: maximum time limit reached". Also, V-Ray waits for the current progressive pass to finish after the time limit is reached, it doesn't stop immediately. This could cause such behavior if the progressive passes take a couple of minutes each and the prepasses finish around the time limit.

[palibebeh]

Ok I see, thanks!
But would it be possible to maybe make it an option to choose if the time limit corresponds to whole rendering (with prepasses) or only to final pass? Sometimes differences between frames in prepass times are very big, and this results in final renders of very varrying quality - especially in archviz, when you set up your camera to different angles/rooms/light conditions in different frames, and want to render it in a sequence.

[anthonyh]

For animation backburner is set to render in blocks of frames, I`d assume the first image in the block would render slower because of the loading of assets and the subsequent frames of the block would then render quicker because the assets are already loaded. The same seems true when you first load a scene, the light cache is slower the first time then faster from then on. Wouldn`t that cause that first frame to render worse compared to the others if including the prepasses in the calculation ?

[radoslav.platikanov]

To achieve consistent frame quality, it's best to use the noise threshold to control the quality and render time, not the time limit.