Hello there.
I have been asked to create some beamlights but I’m getting artifacts/or missing parts as you can see in the screenshots.
I’m using 3ds Max 2023 and the most recent Vray version.
Any ideas of why this is happening? I have tried many different things that didn’t work. Any help would be greatly appreciated.
Many thanks for considering my request.
Akis
IIRC, reduce the step size/threshold, and possibly increase min AA.
But you can save yourself a lot of headaches by using Max Spotlights and Max’s Volumetric Light Effects for this type of thing. Much faster. https://help.autodesk.com/view/3DSMA…1-54A0A3CD9D62
Hi, and many thanks for the fast response!
Unfortunately, the changes in the suggested settings did not work.
I found a temporary solution using Max Spotlights for this project, as you said, but they don’t give the same effect as the Vray ones.
I hope I find the reason behind the Vray fog and lights issue.
Sorry it didn’t help. I know I have seen this issue before, and I am pretty sure it has been discussed here as well. Maybe it is a scene scale thing, as in a simple test scene I had no problems getting thin beams with default settings. I tired VRay lights, rectangular or disc (Directionality at or near 1.0). I tried Max Spots with VRayVolumeFog as well.
It looks like you may not be on the latest VRay, or you would have a Directionality Strength setting if you were (not that this setting is the answer, but perhaps the newer version is harder to break in this regard, because I have seen this issues before, but now I am having trouble reproducing it).
You could try lowering the Cutoff for the light, especially 0.1 seems very high.
OK, I did just see the issue with decay turned off (or set very far, as there is no longer a No Decay setting). (Edit-- not related to decay it seems) The IPR or Progressive always seemed to resolve it at default settings, but with the bucket renderer I set the Min subdivs (AA) to 2 and it solved it. Increasing Min Shading Rate also solved it (which is weird, I did not realize that would effect things other than reflections/refractions/GI.). Higher Min subdivs was faster to render than the higher Min Shading rate (also interesting).
Increasing the min AA subdivs usually resolves such issues (they are caused by the light ray not managing to hit the light, hence needing more samples). If it doesn’t help send the scene so we can troubleshoot.
Hi again and thanks a lot for your time. I Appreciate it.
I tried all the above and still nothing works. I have no idea why this is happening but I’ll make sure to leave a post here when/if I find the solution to the issue.
Hi there and thanks for the reply.
Unfortunately increasing the min AA subdivs didn’t help. I’ll make sure to send the entire scene for troubleshooting.
Thanks a lot for doing it for me, it’s not the first project it has happened so I would surely appreciate some help.
If you ever do find the solution please do post here.
Thanks for the provided scene. You have a ton of lights and the Adaptive Lights setting is set to its defaults. You need to either increase the amount or use Full Lights Evaluation (will be slow).
Hi and thanks for such a quick response. I really appreciate it.
The Adaptive Lights option didn’t help at all even if I increased the amount a lot.
The Full Lights Evaluation can do the job but the render time is almost infinite. Even with the Chaos render farm is impossible.
I deleted all lights apart from the beam ones and the result in both cases is as per attached.
However, I need all these light instances because I have been asked to provide an aerial render of a hotel during an event at night. Do you think it is possible to achieve that?
Thanks and regards,
Akis
Hi, one possibility is render the beams separately and add them in post. Using the VRayLightMix and the other render elements can make this an easy task. You could also try with Volume Light instead of VRayEnvironmentFog and standard lights for the beams. This won’t produce as realistic result as the VRayLight though.
The adaptive lights thing makes sense. I wonder if increasing the number of Light Cache subdivisions would help, giving it a better chance of finding the correct light. (Like to 10000-20000)??
Increasing LC subdivisions would definitely help (I just noticed you are using the default 1k samples). Also, to speed things up increase the VRayEnvironmentFog’s Step parameter - it’s far too low. A rule of thumb is Steps = Fog distance divided by 2-3.
This is something I was going to suggest (of course you meant ‘increase’ rather than ‘reduce’) should help.
I ran a few tests and the randomly tweaked attached image took 9:26 and I’m confident it can be reduced further.
That’s using a now pretty old 3950X.
EDIT: I should have said that as a baseline the scene is using 40 lights, adaptive lights set to 40, LC 2000, default AA/everything else.
Env fog as set in the OP’s screenshot but with 8000 distance/1000 max steps.
So yeah…I can’t see any real issue with this, as long as it’s tweaked for the scene to get the best times, which for this example I reduced to a few minutes (attached), or seconds depending on some acceptable hacks.
There is one little thing I noticed. As you can see in the attached, where there are odd outlines in some areas and and smudging on the left side and lowering of light value in those few beams.
Maybe that’s some bug or is soluble in another way.
This wouldn’t be a problem in any final render though, as if I was doing this, I would hide all unnecessary geometry and just render the volumes to comp later.
Obviously a larger step size is faster, but what effect, if any, does the step size have on the dropout issue? @fixeighted were you saying it actually works better with the higher step size as well?
If you are setting the Adaptive Lights to the number of lights in the scene I wonder if LightTree would be slightly faster?
Perhaps I will give it a little play. Just got my 7995WX system. Eager to play (once I get through all the setup hell).
What I’ve noticed is that the step size has no effect on the dropout, at extremes of high/low, and there’s no apparent massive speed increase actually.
Maybe that’s due to the setup of the lights; i.e. it’s not a solid volume using a texture that needs sampling through, or lots of crossing beams at variable distance.
The single impactful factor is the adaptive setting, with the exact number and light tree giving comparable results I think, though maybe I’d opt for picking an amount equal to scene lights, to avoid any surprises, especially
as I imagine this is an animated scenario.
In any case, if it was my project then I’d split it into bits and comp later for ease/speed, and to get around those awful outline glitches that occur with geometry.
Thanks for mentioning your really really really fast new kit while I suffer with antiquated old crap :twisted:
Just got my 7995WX system
Congrats and many trouble-free hours of using it.
@akis_kyriakopoulos if you can’t manage to fix your scene on your own, please send it to support. We might be able to help you.
@fixeighted I did finally get Max running on the system (2023 at least). I was able to play a little bit with a similar setup of lights. With 101 lights I was sometimes getting dropouts even with adaptive set to 800. I may not have ever tried the exact number.
Like your results, light tree seemed to make no difference in speed or dropouts. Full evaluation was definitely slower, even in this new beast.
The post comp approach seems to be the only real production friendly (er) solution. Or using Max lights, which of course don’t do all the scattering. I’d like to try an empty VrayVolumeGrid as well. In the past that has been my go to solution for volumetric in VRay, at least for subtle scattering (possibly not light beams).
Sorry to brag about the new system. I had literally just turned it on yesterday and was very excited! After some preliminary testing I am even more excited, as the performance is everything I had hoped.
Hehe…only kidding about new gear…if you have the cash then spend it I reckon …bigger/better ftw! 
I don’t have a need for this type of volume situation right now, so I won’t spend more time on it (well, maybe a look at that empty grid thing you suggested) but I’ll keep
an eye on the post for any cool technical epiphanies/updates 8)
