Render time increases with every frame

[gremmler4ARLU]

I’m rendering an image sequence with X-Particles (cached and un-cached). The render time gradually rises from 5 seconds at the beginning till 1 minute at frame 600 (CPU and GPU). The complexity of the scene does not change significantly and when rendering any frame in IPR, it only takes 5 seconds.

Btw, I found a similar post in MAXforA: https://forums.autodesk.com/t5/arnold-for-3ds-max/arnold-render-time-increases-with-increasing-frame...

[peter_horvath]

What's your Cinema 4D and C4DtoA version? Windows or Mac?

Could you please run the render with enabling file logging and setting the verbosity level to Debug and send me the log of one of the first and one of the last frames to compare?

https://help.autodesk.com/view/ARNOL/ENU/?guid=arnold_for_cinema_4d_ci_diagnostics_ci_log_html

[gremmler4ARLU]

Strangely, now the render time increase less, but sill considerable. Attached the log files.

Render time of frame 60 was 6 sec. Render time of frame 240 was 17 sec.

When rendering both frames in IPR, the render time of each is just 2 sec. The simulation of the particles takes only one second per frame. And for the IPR render, I let the simulation run in the viewport till frame 60 and 240, so the scene complexity and rendered images are the same.

C4D version: 2024.2.0 on Windows, C4DtoA version: 4.6.6.2

[gremmler4ARLU]

I've updated to C4DtoA v.4.6.7.1 (as v.4.6.7 can't render in GPU mode). Render time is a bit faster, but still increases every frame. C4D's Picture Viewer indicates most of the time per fame is used for "exporting...", which does not happen in IPR. Also: GPU render is till buggy. After 180 frames, the render stops unexpectedly. Console error message: "no GPU matching requirements found for GPU-rendering"

[peter_horvath]

I wasn't able to reproduce the issue so far. I've only tried in a basic scene, with an xp emitter and 100k particles.

I'm wondering if there's something specific in your scene that causes the render time increase (which from the log seems to be happening during scene creation indeed). Would it be possible to share your scene? Or can you try to render a basic scene to see if the problem persists?

[gremmler4ARLU]

Maybe it's related to cache, as mentioned in this MtoA topic: https://forums.autodesk.com/t5/arnold-for-maya-forum/arnold-render-time-increases-with-increasing-fr...

The same issue appears in another scene that uses the Point Cache Tag on complex splines. If I delete the cache, the render time is normal again.

[peter_horvath]

If that's the case, that might be a more generic Cinema 4D issue, not Arnold related. You can verify it if you render with another renderer. Simulations tend to always run from frame 0, thus each frame takes longer and longer to compute. Although that's what caches supposed to solve.

[gremmler4ARLU]

Just rendered the scene with the standard renderer and there is no render time increasement per frame

[peter_horvath]

Can you share the scene with me?

[gremmler4ARLU]

The scene was a bit messy. When cleaning it up, it seems that after removing a Vertex Map uses Delay and Decay, the render time became normal. I had a similar issue right now. Maybe if Arnold is using Vertex Maps that involves Delay and Decay, the steps of the Delay and Decay causing the issue?

[peter_horvath]

> Maybe if Arnold is using Vertex Maps that involves Delay and Decay, the steps of the Delay and Decay causing the issue?

Arnold does not do anything special to Vertex Maps, just reads the stored data. If Delay and Decay causes a slowdown generating the data, that should not be specific to Arnold, but you should experience the same slowdown in other renders as well.

Can you share a scene that shows the issue?