Quality Disparity between Film and Render Regions in Photon Tweet

[Maxter]

Hi,

I'm currently rendering a scene with the photon tracer kernel, and I noticed a significant difference in
image quality between the film region and the render region. For example, the film region renders the
image part in 22 seconds, while the render region for the same part takes 144 seconds. The caustics in
the render region look much cleaner, but the diffuse and specular components appear the same. I suspect
that somehow the render region is casting more photons for the caustics. Additionally, when I disable
adaptive sampling, the image quality, noise, and render time remain the same for the film region.
I have never encountered this issue before.

When I switch to the path tracing kernel, this difference doesn't appear.

I'm using Octane 2023.1.1.

Cheers

[bepeg4d]

Hi,
please note that Film and Render Regions are working differently with sampling.
While Film Region is stopping at the same Max Sampling chosen in Kernel panel, the Render Region doesn't stop and continue till 1Million sampling.
Since GI Clamp is set to 10, you cannot see any difference in Path Tracing in this case, because caustics are already killed, try to set the Gi Clamp to max value.

ciao,
Beppe

[Maxter]

Hi,
please note that Film and Render Regions are working differently with sampling.
While Film Region is stopping at the same Max Sampling chosen in Kernel panel, the Render Region doesn't stop and continue till 1Million sampling.
Since GI Clamp is set to 10, you cannot see any difference in Path Tracing in this case, because caustics are already killed, try to set the Gi Clamp to max value.

ciao,
Beppe

Shouldn't the result be identical when the film region and render region reach the same sample count?

[bepeg4d]

Yes!
Here is what I get at roughly the same sampling level and Adaptive Sampling enabled:
With Film region at 3000 samples:

And with Render Region at 3102 samples:

Could you share your scene via Private Message, so we can check?

ciao,
Beppe