Iray - do not increase Min Update Samples and Update Interval

Michal P.

Problem description:

When I increased Min Update Samples to 10 nad Update Interval to 10 in Render Settings for NVIDIA Iray I had the following problem during rendering:

The DAZ Studio started renedring process. After random time the GPU stoped rendering process (the render was not finished) but DAZ Studio was thinking that the GPU is still rendering. So I had to cancel the rendering process very often before it was finished.

It was very difficult for me to find out why it was happening because the problem started after I have upgraded to DAZ version 4.16. And so I thought the problem is in new version. But when I rolled back to version 4.15 I had the same problem. I think the problem is caused by Windows watchdog. The GPU is too bussy for too long time so the Windows watchdog kills the rendering process. I do not know which one of these two parameters causes the problem but when I set it to default value (1 and 5) the problem was solved.

prixat

What is the windows watchdog?

I render with Min. Update Samples at 100. It allows the GPU to do it's work with fewer interuptions and often (but not always) speeds up a render. I've not had a problem with changing the value.

Michal P.

"What is the windows watchdog?"

When some process keeps some hardware too busy (like GPU) Windows kill this process. We had similar problem when we do programing GPU kernels. It is possible to change time out for those watchdogs. When we increased the value, the problem disappeared. In Microsoft Windows XP SP1 and later operating systems, GDI uses a watchdog timer to monitor the time that threads spend executing in the display driver.

I am not 100% sure that it is exactly the case but as I said when I set Min Update Samples and Update Interval to default values the problem was solved. It can be hardware specific. I think the slower GPU the higher probability. I have experienced the problem more often on 1080 than on 1080 Ti.