Chaos Corona for 3ds Max > [Max] Bug Reporting

Backplate + Sun causing shadow bug

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PastaJackal:
This has been posted before, but I wanted to see if anyone had a workaround of any sort to deal with it

The issue occurs when a scene backplate using CoronaLightMtl is setup with a CoronaSun (most evident when sun is facing the camera at a low angle), there is a large shadow artefact which appears on surfaces with less than 0.8 glossy reflection. This becomes a huge issue when creating images using drone photography which only wraps around a cylinder correctly rather than a dome or sphere which could be plugged into the environment map channel. So essentially, any shaders with low glossy values are vulnerable to some very ugly jaggy shadows creating a highly unrealistic result.

I'm wondering if any others have found a way to work around this as I understand this bug may be too difficult to completely resolve. Even implementing some kind of cheat in the next version (I'm using 1.7 hotfix 2) solely for these situations would be great.

Thanks for reading!

James:
Try turning on caustics in your window glass.

PastaJackal:
Issue occurs even without glass or other elements present.

In this example, the backplate material was created with a CoronaLightMtl plugged into a CoronaRaySwitchMtl with GI channel left empty (this is to avoid using max's object properties to eliminate shadows and GI contribution).

Have been testing numerous methods like CoronaMtl self-illumination but all fail.

The only real way I can see of getting it to work is by creating a spherical map (not sure how to do that when some backplates are incomplete) and using that in the scene environment overrides.

maru:
This is a known light transport bug - https://coronarenderer.freshdesk.com/support/solutions/articles/5000516180-known-bugs-and-limitations
I'll look into this and try to think of some workaround.

maru:
The only workaround seems to be disabling "visible in reflections" for the Light Material.
This will obviously change the way your scene looks (there will be no reflections of the background anywhere).

Sorry for this. It's a known issue, reported many times, and a very serious one. We are aware of that, and I am sure our team will find a solution, but right now we don't have any time frame when it could be expected...

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