Euler_A + Z Image Turbo ?

[JohnLoveJoy]

Why does Euler Ancestral work with Z Image Turbo in ComfyUI, but produce blurry, noisy images in KoboldCPP/SD.cpp?

[LostRuins]

As far as I know ZiT was designed to not use ancestral samplers. Could comfy be silently swapping it in the background? The samplers are universal so if Euler A was broken you'd see that in other models too (but it works fine in SDXL)

[JohnLoveJoy]

As far as I know ZiT was designed to not use ancestral samplers. Could comfy be silently swapping it in the background? The samplers are universal so if Euler A was broken you'd see that in other models too (but it works fine in SDXL)

I thought that too. Then, I've noticed that many people in the Stable diffusion community have been using ZIT with Euler Ancestral for better quality.

https://www.reddit.com/r/StableDiffusion/comments/1rzyu7l/zit_and_klein_steps_details/ https://www.reddit.com/r/StableDiffusion/comments/1ryhjf2/simply_zit_check_out_skin_details/

[LostRuins]

Maybe @wbruna might know

[wbruna]

I've looked into this before, but didn't come to any conclusions. As you've noticed, the sampler code is exactly the same for all models; but no noise-injection sampler works right with DiT models (e.g. the Flux+Euler A issue). Comfy must be doing something different to the noise levels.

I'll see if I can figure out a way to adapt it.

[wbruna]

It turns out ComfyUI switches the implementation to a flow variant under the hood, so "Euler Ancestral" isn't really a single algorithm...

https://github.com/Comfy-Org/ComfyUI/blob/v0.18.1/comfy/k_diffusion/sampling.py#L217

Anyway, I was able to put together a tentative implementation for stable-diffusion.cpp: leejet/stable-diffusion.cpp#1363 . It needs a huge refactor before being included upstream, though, so it may take some time to reach Koboldcpp in a proper way.

@LostRuins , if you think it'd be worth including right now, I can cook up a minimal self-contained implementation for us, and replace it with the upstream version when it gets merged.

[LostRuins]

I'll probably wait for it to get merged upstream to avoid further divergence.