Chaos Corona for Cinema 4D > [C4D] I need help!

Directionality on mirror / glass

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masterzone:
Why doesn't the directionality of the Corona light get affected by mirrors or glass?
This happens on mirror and glasses...
Any tips?
Alex

TomG:
There is the checkbox "prevent black appearance". Then there is the solution of having a second object with a light material set not to emit light and set to no directionality to act as the visible part that will show up in reflections, to go along with the light object. Other than that, it is physically correct, since due to directionality no light rays from the light source actually hit the mirror, so do not get reflected. The workaround is relatively close to physical reality (where the physical reality is that mirrors, glass with imperfections, etc. actually bounce and bend rays outside of any perfect directionality, and those do reach the mirror - this could be set up in Corona I would say, but would be harder to set up and slower to render than the "have two objects, the light to emit light with directionality, and another to act as the visible part of the light")

masterzone:
Hi Tom, thanks for your reply.
I understand the technical reasons you explained to me, but in this context, the directionality behaves in a strange way.
I don’t understand why it has to hit the mirror to become white.
Does the directionality simulate the blades of a spotlight, or is it just an internal parameter that mimics the effect of spotlight blades?

Maybe in this case, it would be better to use an IES light…
In the scene, I tried moving the camera behind a glass shower, and the light remained black.
So maybe the directionality works differently from spotlight blades.

maru:
The "prevent black appearance" option only works for direct visibility, not for reflections or refractions. It's a known issue.
(Report ID=CMAX-1465)

masterzone:
thanks Maru and Tom, now all is clear.
I hope for a future fix.
Alex

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