Thin gray line occurs on walls with rectangular light

[siggi40]

When I put a rectangular light even invisible and double sided in my interior scene, I can see a thin gray or black line all around the walls in the same height with the light. What is the reason for this, is it a bug or how to avoid ?

[dalomar_cg]

Re: Thin gray line occurs on walls with rectangular light

The rays from the light must be traced at some angle that is not parallel with the surface of the light. That thin gray line is the point on the wall that is basically parallel to the surface of the light.

How to avoid it...I'm not sure...Micha might have some better thoughts on that then I would. I typically try to keep my lighting schemes pretty close to what the lighting would be in real life, so I usually have the lights themselves either recessed in to the ceiling or within a fixture/shade of some kind.

[siggi40]

Re: Thin gray line occurs on walls with rectangular light

Can you expand this explanation "or within a fixture/shade of some kind.." ?

Thanks ;D

[dalomar_cg]

Re: Thin gray line occurs on walls with rectangular light

For Example a Lamp would have a shade, so I would put a rectangular light were the light bulb would be and then have a shade around it.

I'm not really sure how else to explain it...just look around at all the lights, and chances are they aren't just a light bulb hanging out, there's typically something to reflect/filter/give direction to the light.

[Micha_cg]

Re: Thin gray line occurs on walls with rectangular light

The reason is, that normaly the light intensity is dependent from the angle between light surface and object. Less light is send out in a very flat angle than in perpendicular direction. Thats life, but Vray allow you to "ignore light normals" (light options). Tested here and works fine.