Stubborn fireflies when using HDRI in Reflections Override

[Dippndots]

So I'm having this problem where using a different HDRI in the reflections override slot to the scene environment lighting slot is producing a lot of fireflies that denoising can't take care of.

The attached image is 75 passes on this region took 1:48, denoised at .6 took an additional 3:40, and really didn't make a difference, so I'm tempted to assume these over-bright pixels are messing with the denoise calculation too.

Highlight clamping was to 10 just to see if that helped, it didn't have much impact.

Both hdri's are .hdr, using the reflections override HDRI in the scene environment instead don't produce the fireflies, and using a .jpg of the HDRI in the reflection slot doesn't produce the fireflies either. This happens with a reflective override material as well, the grey metal has no reflection/gloss/bump maps that would cause speckling.

Is this some sort of conflict between HDRIs?

[romullus]

This is known bug: https://corona-renderer.com/bugs/view.php?id=1257

[Dippndots]

Good to know, haven't tested this in the dailies yet.

[Philip kelly]

Is it a polygon ,, ie not shelled?
If so shell it it will get rid of the fire flies.

Phil

[Dippndots]

Hi Phil, its a closed object.

[maru]

This is known bug: https://corona-renderer.com/bugs/view.php?id=1257

I have just checked and this is not happening in daily builds. So one solution is using them.

[Dippndots]

Uh Oh... I just tested with the latest daily and it's even worse. Let me try to setup a simplified scene to send over.

[maru]

Wow, then it must be something different. A sample scene will be appreciated.

[Dippndots]

ugh, nevermind, it was the geometry, my coworker had it auto-smoothed... as soon as I cleared the smoothing groups it looks fine. Well, at least that's solved.

[maru]

Oof. Can you double check if it's really fixed? :)

[Dippndots]

it definitely works, but if PBR mode is ticked, it breaks again

[Dippndots]

maybe move this to bugs if it hasn't already been logged?

[maru]

I will see if I can reproduce this, and then move this thread to bug reporting, or submit a Mantis report. Thanks for the involvement!

[maru]

Hmm... I wasn't able to reproduce this. Can you help? A scene with the specific HDRIs used would be great (if you can't share them publicly, you can contact us via https://coronarenderer.freshdesk.com/support/tickets/new). I am not really getting any fireflies with 1.4.1 or 1.5.

[Dippndots]

hmm, interesting. Ok, I'll simplify the scene, its a Peter Guthrie and CG Source hdri, so I should probably make a ticket.