Author Topic: Fireflies when HDRi used only for reflections (only in Corona v7)  (Read 959 times)

2021-09-28, 11:13:09


  • Active Users
  • **
  • Posts: 5
    • View Profile
Hi all,

We've moved to corona v7 in the office and I think we've just found a bug.

On our scene we are using two Corona Sky objects, with two different HDRi's. One Corona Sky object is set up just for only GI (so Visible directyly, reflections and refractions are turned off) and the other one is set up the other way around (only Visible by GI is marked). This way the scene is lit by one HDRi but the visible sky and reflections come from a different HDRi.

The thing is that, when we do this, a lot of fireflies appear on the scene, specially around very glossy objects, making the image useless for production.

I've been trying different setups with very simple scenes, and this bug appears to happen everytime you use a Corona Sky with and HDR with "Visible by GI" toggled off. I mean you don't even need the second Corona Sky for GI. What is mandatory is the use of an HDR, it doesn't happen with Physical Sky and Simple Color types.

We are using Corona 7 hotfix 2. This bug didn't happen with Corona 6.



2021-09-28, 12:03:53
Reply #1


  • Active Users
  • **
  • Posts: 71
    • View Profile
i confirm this same issue but also in earlier versions 4-6, when I used an HDR as a seperate background with reflections.
your fireflies will disappear when you use a tonemapped JPG or PNG version instead of the HDRI
Koen Van haesendonck
3D-lab -

2021-09-28, 12:20:50
Reply #2


  • Corona Team
  • Active Users
  • ****
  • Posts: 4041
    • View Profile
Reflection overrides causing fireflies is a known issue, most likely it will be resolved by a fix recently introduced in Corona 8 (this is in the latest Max daily for testing,, so will make its way to C4D once we know how well it works).

2021-09-28, 18:20:15
Reply #3


  • Corona Team
  • Active Users
  • ****
  • Posts: 50
  • Benjamin
    • View Profile
    • Corona Renderer

If you're using a second Corona Sky object just to replace the Background, then you can use a tone-mapped JPG version of that HDRI (since it won't be used for GI and etc.)
Note: You can also use the Direct visibility override at the Render settings instead of a second Corona Sky object, but still use a JPG file.
Please try it and let us know the outcome.