Artefacts / Tiling with DL Kernel Tweet

[dough-cgi]

I have a problem that is drving me nuts: My renders with DL Kernel have a visible seam in the image (Not Texture Related).
At a certain size with the Preview Window, there is a seam in the middle. At 1080p the image has 3 seams (in the attached image, you can see it in the preview, the final denoised image has these 2 seams as well.

I have the latest Geforce Drivers, latest Octane version (although V.2020.1.5. has the same behavior).

Filter size and ray Epsilon is at default (1.2 and 100 um).
PMC Kernel works and does not have these seams.

Help would be great!

[scooternva]

Yeah, I've seen that happen with the Direct kernel. (Quick question: your camera isn't behind a polygon or something, is it? And are you using diffuse GI?)

I'm sure Juan will weigh in here but my understanding is that the biased Direct kernel is great for fast previews while modeling, texturing, and setting up long-running scenes, but not so great if you want photorealistic results (or you run into bizarre artifacts like this). You said this doesn't happen in PMC, but what about the Path kernel? I know it's slower than Direct, but it gives gorgeous results most of the time and it's definitely faster than PMC.

[dough-cgi]

Thank you for your reply! I know it DL Kernel is supposed to have a few flaws - but I use it all the time and experience basically none.
The camera is moving free, not through any object. The tiling happens in all the scenes that happen in this box, no matter where the camera is placed. The line(s) also stay perfectly in place, whether it is divided in the middle or divided into 3 parts (the position of the camera does not matter).

Path Kernel has the same tiling problem. PMC is the only one not making that problem. So instead of having 40 seconds per frame and no noise, I have to render at almost 3 minutes instead with quite some noise remaining....

[dough-cgi]

Oh, and the bottom is 1 big quad poly....and tiling it has no changing effect.

[scooternva]

That is so bizarre. It looks like tonemapping or denoising is only be applied to a piece of the image. It's not a line in your images, it's an entire section of the image that looks different.

If I were you while you were waiting for Juan, I'd check these out (cause he's prolly gonna ask the same questions):

• I noticed both of your GPUs are enabled for rendering. Does the same thing happen when you render only with GPU0? With only GPU1?
• If you're using either tonemapping or denoising, did you try turning those off?
• Does the variant image area appear immediately in the output preview window as soon as the render starts? Does it gradually manifest itself as the render is in progress? Or does it only appear at the very end in the final image? (If it only appears in the final image, something is happening during post-processing; e.g., with denoising)
• Are you seeing any obvious warning or error messages in the Octane log?

[dough-cgi]

Thanks again for helping with the troubleshooting.

I have found the solution to the problem now. It was the window in the scene. I made the dusty window framing with a material mixer node. For the edge I used Octane Dirt Shader. The result seems to be a very reduced amount of rays / samples inside the box, because the transparent part of the glas seems to block most of the rays. The renderer tries to compensate and fails. On the big flat surface, this was the most visible.
Once I simplified the scene even more, the ground almost had a checkered pattern and even more pronounced tiling on top of it.

The solution: I created an texture image as mask for the material mixer node replacing the Dirt Node on the window - it looks the same, but it does not block the rays / samples.
I might not use these terms right though, this is my basic idea of whats going on behind the curtains

Might be a bug somewhere in this with the Dirt Shader - but maybe it was a stupid idea to use it in the first place. I know texture map is better, but here it was just very convenient while searching for a look...