Strange Shading from Env Lighting for Interior

[apjasko]

See attached. My scene is throwing some strange shading from the environment lighting. I'm using all corona lights with the exception of a few target lights from a converted model. But that light select pass looks perfectly fine. Does anyone know what's causing this? The issue seems attached to env lighting, using the Max environment or Corona, provides the same issue. Use of Corona Sky, solid color, or HDRi still provides the shading issue.

I have a deadline Monday so it's critical I resolve this. Any help would be appreciated.

[Tanakov]

That shade looks like sun. Its there a chance you have set sun to 0 but still "on"?

About the rest:
it looks like the fireflies are caused by the amount of glass that you have in your scene.

Try hiding all the glass, its possible its not set to thin.
If that will work, try changing its material settings to "thin" and make those planar. Not all will require than, but probably those on ceiling.

Do you have any reflections set to 999? Did you check albedo?

[pokoy]

IIRC, there were issues with 1.6 where using CoronaBitmap for environment lighting could produce similar artifacts, it was fixed for 1.6HF I believe. If you can't get rid of this, make sure to provide the scene or a similar repro case so it can be tracked down.

[apjasko]

Thanks for the replies, guys. The shading issue was visible in the bottom right of the images. It isn't the fireflies that I was concerned with. I attached the final production of the image zoomed in on the problem area. I resolved it for the most part in order to produce for the final. Regarding Tankov's questions about reflections and fireflies, I have started using a ray switch material on my metals and dielectrics with a glossiness of .6-.8 to reduce absurd amounts of noise and fireflies bouncing off these materials. Do you advise this as a means to reduce noise? It seems to work wonderfully and on other scenes they seem to render quickly to a low noise level.

I'm running the original 1.6 build and haven't upgraded to the hotfix because of work load lately and didn't want to disrupt the workflow that was working and predictable. I have been rendering this scene for a few days and discovered the shading issue a round or two ago. I don't have a sun in the scene and I was using rectangular lights to fake extra lighting (off to diffuse, reflection, refraction, and occlude other lights) in the foreground and it seems this was causing the issue. I was turning off those lights in lightmix and it really exaggerated the issue. It seems the environment was shading one portion of the floor, and these fake lights were illuminating the other portion. As if the environment still saw those lights despite the occlude other lights being unchecked. When I set both to the same value in lightmix, this seemed to balance the issue out. It isn't even apparent in the crop attached.

If the issue occurs again I'll upload for the Corona team to investigate. In the mean time I'll upgrade my workstations to the hot fix.

[Tanakov]

I use RSwitch a lot but someone once told me that this causes some extra noise in the long run.

But I my self noticed that this is indeed quite a helper.

my tip is remember to add RS material same bump as oryginal.

[maru]

I am afraid it could have been one of those "dark highlights when light passes through fake lights/materials" issue, which started appearing after fixing the troubles with reflections of solid glass. It sometimes happens in case of lights with "occlude other lights" off, and similar "hacks" which are not really physically correct. More info can be found here under "light transport issues" https://coronarenderer.freshdesk.com/support/solutions/articles/5000516180 and I will also try to reproduce some of the issues and update the article with examples.

If it ever happens again, or if you could share the original scene with us (preferably reduced, so that the problem is visible, but it's not a huge file), that would be appreciated. I also recommend to contact us at support@corona-renderer.com next time instead of posting on the forum, or in addition to posting on the forum.