GPU usage spikes; high res renders

[gristle]

I've just completed a set of renders, the smallest being 6000 pix square.
Firstly, I tried rendering as a full frame (Octane 3.05.3.0) but noticed the GPU usage would peak every 5-10 seconds then drop off. The GPUs would just start winding up, then slow down.
Memory on the GPUs was not an issue, using 1/3 of available memory. I tried messing with every setting I could think of; priority, parallel samples (mentioned in another thread) but to no avail.

In the end I split the render over 4 frames and key framed the shift camera. No tile larger than 3000 pix square and the GPUs were charging through the renders like normal.

Has anyone else come across this issue?

I did a comparison. One of the original frames, unsplit, was cancelled after 2 hours and it was about 20% complete. The same image, when split into 4 was complete in about 3 hours.

[juanjgon]

Hi,

Have you tried to render the scene disabling the tone mapping for all the GPUs? Well, not all, at least one must be enabled. This option is in the GPUs configuration panel.

Thanks,
-Juanjo

[gristle]

Yes, tried that. Even tried assigning tone mapping to the display GPU but caused a hangup.

I don't think this problem is limited to this version, I remember a year ago having a similar issue but I could not be bothered finding a work around.

[juanjgon]

Are you using the LightWave compositing feature to add a background or foreground plate? I've found that this feature is currently very slow if used with high resolution images.

Thanks,
-Juanjo

[gristle]

I had a low res BG plate to match angles to, but then removed it.

There seems to be a sweet spot where Octane will render slowly, somewhere over 3000 pix square.

Does physical RAM amount come into play with rendering at all?

[juanjgon]

Some CPU RAM is used in Octane 3 to store the frame buffers and so on, but usually the CPU RAM is not a problem. How much memory does your computer have? You should see a lot of HD activity if you are running out of RAM.

-Juanjo

[gristle]

16GB, there was no paging happening during rendering.

I tried direct lighting as well, same issue.