Agree that the default light bounce can be higher, there can be some really obvious difference:
Probably also volume:
I have heard several times people complaining to me how Cycles volume scatter is dirty and heavy, then I asked them whether they set the light bounce higher, they would tell me they never touched it, didn’t even know it exists. So I think it makes sense to have the default be higher.
While I agree that 4 glossy bounces is not enough for rendering glass, 10 bounces is usually more then enough even for ill cases. It would be cool to make trapped rays escape glass after the last bounce by default, not just them being killed causing black areas around glass lips. So far I have to repeat the same shader setup over and over. Dispersion also would be welcome, but that requires either random per ray or spectral rendering =)
Is the dispersion parameter for transparent shaders planned for any future of Cycles, please?
Not Transparent shader I think. But generally speaking I imagine that will be the task of the future for the Spectral Cycles branch after it completes the initial merge (hopefully in 3.1 or 3.2) :
This is probably not related to the topic here so if we are to discuss more about dispersion we should better move on to the the spectral thread.
Hey, I have CyclesX crashing on so many scenes currently random.
How can I see the crash log? To report the bug
Christensen-Burley SSS is back for now:
https://developer.blender.org/rB73a05ff9e83a31be34d32a92cd5fb4d17994e342
I’m looking into this, we may add it back as a pass independent of denoising.
If you’re on Windows, the Blender install folder contains a blender_debug_gpu.cmd that you can run to generate debug logs. Generally, more important than crash logs is a .blend file to reproduce the problem. And then if we still can’t reproduce, a crash log can help.
Great!! Today I was using 2.93 at work and I just came in a situation where Random Walk just didn’t work but Christensen-Burley did very easily, and I wished we could have it back in 3.0! Thanks Brecht!
Thanks for taking time to reply Brecht, It’s awesome that you are looking into it! Fingers crossed to see it back in, independent from denoising seems even more fitting to such a useful utility pass. Thank you for all your incredible work!
No clamping can produce more noise in general, not just fireflies. But default value could certainly be increased to work better with the sky texture. How much clamping will darken the image depends on exposure and lights, but value between 30 and 50 should give better results out of the box.
Christensen-Burley SSS is back for now:
Thank you Brecht !
Hey have the bug of everytime i render Blender crashes with AS at a random position → when not when a new Tile starts.
https://developer.blender.org/T92158
Have you seen this?
Nice paper the results are pretty impressive 
I have taken a look at this and I can confirm that something is not right. I left a comment with more details on the bug.
I have done some tests with Christinsen-Burley in 3.0 and unfortunately it does not work. Christensen-Burley produces so much noise in 3.0 that even with 10 times higher sample rates you still have a lot of noise.
@Brecht:
Are there any ideas or plans to incorporate the capabilities/features of Christensen-Burley into a variant of Random Walk (Burley)?
Is there perhaps a bug in Blender’s version of Random Walk (FR) that prevents proper light scattering and refraction. I appreciate your efforts to reintegrate Christensen-Burley in 3.0, and you have already pointed out possible problems due to the different way Cycles X works, but Blender needs the ability to correctly render translucent and transparent materials that are backlit. (light refraction and light scattering etc…)
If Christensen-Burley cannot be integrated into Cycles X, then SSS in Blender works only with significant limitations, then it urgently needs an alternative.
Maybe you should think about leaving Cycles in 3.0 next to Cycles X.
I think that if you release 3.0 in december or january, then a lot of users will complain about the missing capabilities of SSS in Blender, because that is a major regression.
If you want us to improve this or random walk, we need an example .blend file that shows the issue.
There is no practical way of doing this, it will not happen.
Hi.
The difference between regular noise and fireflies is that regular noise is easier to decrease by increasing the render samples relatively not very much, which is not always the case with fireflies.
Clamp indirect=30 still produces some noticeable differences in lighting power compared to non-clamping, for example in the BMW scene in headlights of the car. I think clamp indirect=50 would be fine.
I did some SSS testing with Christensen-Burley on an object that looks really bad with Random walk. While it’s true that C-B needs more samples in 3.0, everything also renders much faster in Cycles X.
Here’s 2.93 render at 256spp:
So overall a bit of an improvement . Of course the issue is that the rest of the scene would have to be rendered with more samples as well, which could be a problem. For that, adaptive sampling should help, but I ran into the same problem that I reported before, where dark areas are undersampled. In this case it’s even causing denoising artifacts in the final render (dark spots in the bottom right).
@brecht, have you been able to look into this issue?
I hope devs calculate noise threshold on the sRGB data and not on the linear colored pixels, because an evenly noise distribution in linear space transforms to undersampled blacks into sRGB. Means you need a gamma-distorted noise threshold to get it neat looking after the linear-srgb transform.
Would you mind sharing that scene so we all could do some tests? That’s a nice model for testing sss.
