I’m trying to do an emissive LED light pipe in a car that is hidden between the door panel and a grab handle. The problem is that when you see the light source all is fine, but when you hide it out of view it should still cast light on the surrounding surface like in real life. Well it does NOT. No matter what I do it simply goes dark. When I rotate the camera so that I see it, it lights up. How can you get that emissive material to cast light all the time even if the source is not immediately visible?
Pointers, suggestions and hints are very much appreciated.
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My guess is that emissive ligthing is probably only part of the screen space lighting and so it’s not possible to render it when it’s out of view
So am I to understand that what I am trying to achieve can’t really be done with emissive materials but with regular lights?
Could be, that your emissive part is too small to be recognized by Lumen. There is a minimum size for how big an emissive surface has to be to work with Lumen.
From the manual:
"Lumen and Emissive Materials
Emissive materials propagate light through Lumen’s Final Gather with no additional performance cost. However, there’s a limit to how small and bright emissive areas can be before they begin to cause noise artifacts. This is inherently much more difficult to solve than manually placed light sources."
You can test it by putting a normal sphere or cube into your scene and give it an emissive material, then play with it´s size to see, if/when it works with Lumen and then, if it still works, if you turn your camera away from it.
But there seems to be a new setting, that may be able to override that min size rule, something along those lines were mentioned in the Lumen thread:
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Objects need to have good distance fields to work well with lumen, especially with emissives. I’d try making that part a separate mesh, enabling distance fields on it, and probably crank up the resolution. You can check the lumen views to make sure it’s an accurate representation of the scene.
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