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Arnold mesh light shows different ''broken'' lights with each Arnold render

Message 1 of 5
3188 Views, 4 Replies

Arnold mesh light shows different ''broken'' lights with each Arnold render



I'm currently working on my first ''big'' project and ran into some issues while making light bulbs into an Arnold Mesh light. I did the following:

1. Made a sphere

2. Duplicate special 

3. Select 1 sphere > Arnold > Lights > Mesh Light:

     I got an error saying ''The Mesh has multiple instances. Light instances are not supported!''

4. Selected all my objects > convert > instance to object

5. Select mesh > Arnold Mesh light > changed the color, intensity, exposure, temperature and samples (and checked show original mesh, use color temperature, light visible)


This worked for one light bulb so I repeated it for the other bulbs every single one by hand (I don't know if there's a quicker way to do this) but when I checked it in the Arnold renderer I noticed that with each render different light bulbs didn't work. In the first image I did step 1-5 and on the second image I changed the position of the ''broken'' light bulb in between the ones that do work, then I hit control Z to undo it so it was in the same position as before and opened Arnold. Now different light bulbs are broken  (and others seem to work this time). 

Does anyone know what's happening and/or how I should approach this?



Message 2 of 5
in reply to: Anonymous

I have also run into this bug, or at least one very similar to it.  I've spent the better part of this year attempting to find a fix to no avail.  I have also researched extensively, but strangely this is the first time I've come across this post or anyone else experiencing this issue for that matter (though I've seen some similar bugs where the scene stops updating automatically when adding too many new lights, but that is easily fixable by restarting Maya).


I create an Arnold mesh light, usually grouped with some other geometry and then export it and reload it as a standin, but then upon duplicating the standin several times, after a certain point most of the new duplicates emit no light.  And if the mesh light standins are modified in certain ways, the order of broken and functional lights changes randomly, though usually most of them remain dysfunctional. 


Restarting Maya/my machine, resetting preferences, giving each standin a unique name, re-exporting and reloading the lights, exporting and re-importing the entire scene, rebuilding the entire scene from scratch and many other things I've also tried do not ever fix this.  Upgrading to newer versions of Arnold and Maya have made no change either.   I have reproduced this bug multiple times and it appears as though the issue may be worse at large scene scales too.


I greatly hope that this bug will be fixed soon, because it has halted a number of projects of mine and has cost me dearly as far as time wasted on troubleshooting.

Message 3 of 5
in reply to: Anonymous



I may be late, but I'm also encountering this issue. I have just updated my Arnold to latest for this date. I have one model with several small square meshes which I use as lights for a building. It only shows correctly when I split the model into several pieces, so instead of having a model with 60 squares, I have a model with say, 8 squares and it works fine. I'm not sure why this is, and it certainly is frustrating.

Thor Nielsen

3D Generalist


Message 4 of 5
in reply to: Anonymous

A very strange bug. I had this issue where it was flickering the mesh frame it was fine the next it was "broken". After hours of troubleshooting I decided to pull the mesh light group out on their own out of the main group and that seemed to work. I would have reworked the scene but I have hundreds of these things. I am still concerned it may break in the future.

Message 5 of 5
in reply to: Anonymous

I think there's a chance this might be fixed in the latest Arnold (fixed in arnold core and associated plugins). If you have one of these broken scenes still lying around, I'd be curious to hear if the latest Arnold fixes it (available from

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