Co-planar, intersecting, invisible, and light-linked area lights interfere with each other

V-Ray V-Ray for Cinema 4D Issues
1

It appears that two area lights that are co-planar and intersecting will interfere with each other even if they are set to be invisible (and non-occluding) and light linked to different objects. It’s simple enough to resolve by moving one of the lights, but I wouldn’t have expected it to happen under those circumstances so I wasn’t looking for that problem at first. Consequently it took a little time to track down what was going on:

Screen Shot 2022-02-24 at 11.21.08 AM.png
Screen Shot 2022-02-24 at 11.21.08 AM.png902×862 19.2 KB
Coplanar light turned off

Screen Shot 2022-02-24 at 11.20.32 AM.png
Screen Shot 2022-02-24 at 11.20.32 AM.png968×942 17.7 KB
Coplanar light turned on. 2nd light is invisible and light linked to a different object.

I could see coplanar lights having that problem in general (although I’d prefer to not to have it), but if set to invisible and light-linked to different things it seems like this shouldn’t be an issue.

Jay

2

Hello @GMTJay ,

I apologize for the delayed reply.

Would you mind sharing a simple test scene where the issue is reproducible so we can have a look? Thank you.

3

Hi Aleksandar,

Here’s a test file. A couple of things I tested:

  • The issue appears in refractive objects more than diffuse or reflective metal objects
  • Doesn’t matter if lights are set to include the object they’re lighting, or exclude the object they’re not
  • I ruled out the other object having something to do with it (showing up in the reflection, for instance) by turning it off.

Here’s another example render that might show it more clearly:

Screen Shot 2022-03-04 at 10.33.46 AM.png
Screen Shot 2022-03-04 at 10.33.46 AM.png1918×792 73.1 KB

Screen Shot 2022-03-04 at 10.34.34 AM.png
Screen Shot 2022-03-04 at 10.34.34 AM.png1946×920 29.8 KB

Light-link-issue.c4d.zip (88.3 KB)

4

Hello @GMTJay ,

I apologize for the delayed reply.

This seems like a bug and I have reported it in our internal bug-tracking system (bug ID: VC4D-1302). I will keep you updated if we have more information.

Until then, as you mentioned above, the workaround would be to slightly move one of the lights.

5

Thanks Alexsandar

6

VRay has long had all kinds of issues with lights in the same place. I have seen all kinds of weird stuff over the years. I always offset one of the lights a tiny bit.

7

Yeah, it’s usually a bad idea to have coplanar faces, or lights