Render time approximation

[MANUEL_MOUSIOL]

Hi,

Just recently I was rendering out a rather complicated studio setup with glass- and SSS-(liquid) materials on a lot of objects, a lot of lights and a very high resolution (8500x7300px). With my computer I was rendering the whole image in abut 74 hours (29 cascading bottles with displacement are quite something). I then rendered out a second image, with only two of those bottles and a different camera setup (tilt shift) and was figuring it would only take 24 hours. In the end it took around 48hours, which was alright - because I had plenty of time this time, but here is my problem:

Vray´s calculation of the approximate render time is sometimes way off and it was hard to foresee the total render time. Until now I understood that Vray is taking into account the region that the buckets are rendering right now and through this calculating how long the total render time would take, BUT of course not every part of the image will take the same amount of time as the parts right now, so there will be some difference between the calc and the real render time. Thats why I was using the track mouse while rendering feature to render out the empty parts of the image first. The rest of the image was really mostly the bottles, which consist 90% of the glass material and the SSS material inside. You would think that Vray could thus make a good guess at the total render time, but it was always just two hours ahead of the actual render time, adding one second to the approximation every second (making the total render time look infinite). Even I knew that at 6 hours in the render, it wouldnt take 8 hours to finish.
In theory, I would just have to wait for one bucket to finish, check and calculate that time according to the amount of the remaining buckets and I would have had a better approximation than Vray. But of course it is quite a job to calculate the remaining buckets and wait for one bucket to finish, since one is already taking such a long time.

Is there any way to improve that estimation system of Vray?
Most of the time the approximation is quite good and with my experience I can guess how long it would take in total. But in these extreme cases it is hard to calculate and a 24 hours difference is pretty huge.

Any insights appreciated.

Cheers

Manuel

[alexyork]

I've mentioned it before but I feel that Vray could benefit from an optional (this is important) pre-pass calculation that will assess the scene/view and show you areas of high/low detail through some kind of heatmap, with a generated report, and will then go on to prioritize certain buckets/areas of the frame based on that assessed workload. Along with this it could therefore have a better idea of the projected rendertime based on actual image content rather than the rather simplistic "well, these last few buckets took 1 min to render, so the other 90% of the image will take 9 mins to render" that we have now (or I guess something along these lines). This needs to be optional, so it doesn't slow everyone's renders and workflow down, but I think it could be really useful.

[MANUEL_MOUSIOL]

+1!

Would love that feature!

But in my case even with the current render time of the buckets didn't even allow Vray to calculate the rest which i found strange..

[Morbid Angel]

what i usually do is render smaller res, for example we work with 2048x1556 most of the time so I render half of that 1024x778 and extrapolate the render time from that which would be a factor of x4.

[AbeMata]

Yeah if you do what Morbid says, and extrapolate from a small render, that should work well enough.

You can also set your bucket pattern to checker. That way, when the render is 50% complete, you know you can just double that time for the final frame time.