Problems getting polygons to emit bright light into room

[Danielhruby]

I am having a problem today where I can not get any lighting to affect my scene from a lamp fixture I have made. The fixture has a strip of polygons that should emit light. I have tried a couple approaches.

1. I assigned a VRay material to the strip of polys and added a Vray Light Material above the Vray material. I can see the polys are closing, but no light is bouncing around the room regardless of how high increase the Color Multiplier value. If set to 1, the ploys faintly glow, but at 100000, they look white but no light goes into the scene to light the walls and ceiling. Affect GI was enabled. As was compensate exposure.

2. Added an Area light and copy pasted the polygons into a new mesh. I assigned the VRay Light Mesh to the mesh with the copied light polys. no light is emitted not he space if I crank up the Area light Radiance power. Or if I crank up the VRay Multiplier.

3. Added an Modo Mesh light and copy pasted the polygons into a new mesh. I assigned the VRay Light Mesh to the mesh with the copied light polys. No light is emitted into the space if I crank up the Mesh light Radiance power. Or if I crank up the VRay Multiplier.

So, I can get the strip to look bright, but no light is emitted.

[Danielhruby]

Link to problematic file....

https://www.dropbox.com/s/im0d5tkhnn...oblem.zip?dl=0

[John_Do]

Hey Daniel,

I've looked at your scene.

The main problem comes from the fact that the emitting faces are on the same level than the lamp geometry, so the light is blocked. Offseting the faces by 0.5mm is enough to get the desired result.



I suggest you to use V-Ray Mesh Light as much as you can in general, it's much easier to sample than some faces with a V-Ray Light Material. You can do the test on your scene, it's pretty obvious.

Below the result after correcting the scene.

[Danielhruby]

Thank you John,

That helped. I also think that I have to use modo Area light as the Mesh light does not seem to work.

[John_Do]

Yup, you have to use the Light mesh setting located in the V-Ray Light tab in your Area Light properties.