Weird cutoff with linear light

thilgerink · August 21, 2013, 08:19:33 AM

Hi all,

Pretty new to KeyShot, and trying to render some benches that have light strips placed underneath them. Whenever I apply a emissive material to these strips though I get weird lighting/shadow patterns... In the picture added I simulated this with just a very simple bar (area light material added to it) placed over a ground plane. Notice the weird pattern in the light that is cast on the floor on the right side of the bar. Anyone got an idea how to deal with this or can tell me how this is being produced?

Many Thanks,
Tom

Speedster · August 21, 2013, 09:56:35 AM

It appears to be coming from the "end" of the bar. Map it in another color in your geometry, apply flat black to it in KS and try again. For lights, I now put a "housing", or shades, around to mask all but the surface I want to be an active light.
Bill G

thilgerink · August 21, 2013, 10:40:03 AM

Thanks for the fast response Bill! I'll try it. One question remaining though; why is this only happening on the right side of the bar? This was also the case with the LED strips. 3 sequential bars after one another all gave this pattern in lighting, evenly lit from the left side and fading out into this weird shadow on the right.

thilgerink · August 22, 2013, 12:47:39 AM

Updated the file according to the tips Bill gave me. Unfortunately, I still get an a-symmetrical lighting pattern on the floor.
Why is there more light on the left side than on the right side? $:-\$

KeyShot · August 22, 2013, 10:10:32 AM

Is the light source by any chance closer to the geometry on the left side than the right side?

thilgerink · August 23, 2013, 12:34:10 AM

Hi,

No, actually the red rectangular element has an area light added to its bottom face only. The white rectangle is the reflection in the floor (which makes it even more confusing to me, since there the light seems to be evenly distributed $:-\$ )

thilgerink · September 04, 2013, 06:39:29 AM

No idea, anyone :O?

DriesV · September 04, 2013, 07:39:10 AM

I believe the culprit is the tesselation of your emitter plane.
Try this:

Import Plane.obj from the KeyShot resource folder
Resize/scale/position it until it closely matches your emitter plane
Apply Area Light Diffuse material (or copy from existing plane) and hide your 'faulty emitter'

Do you get good/even lighting now?

I've run into the same problem before. I work with SolidWorks and the way it tesselates thin geometry is by extremely stretching polygons. So a rectangular plane consists of 2 stretched triangles. I believe this was the source of the problem. (You can check tesselation in KeyShot using the wireframe material.)
The Plane.obj model has better tesselation than what SolidWorks can do.

Dries