Light beam not rendered correctly with fog

[Basshunter]

What could be the reason for this problem?

[Nejc Kilar]

Howdy!

Could you please try disabling the "adaptive light solver" in the render settings -> performance compartment and then try to re-render? Kind of looks like that could maybe be the culprit, would really appreciate it if you could try it out and report back.

Thanks!

[Basshunter]

Hi Nejc!

I tried turning "Adaptive Light Solver" off but the problem persists.

[maru]

It would be nice to disable the AI denoiser - otherwise it is hard to see the base image quality, e.g. if the noise is uniform or if there are some "holes" in it.
You can try increasing the Light Samples Multiplier in Render Setup > Performance from the default 2 to something like 4-8. It will give you better quality of direct lighting (=what we see inside the fog).

[Basshunter]

Hi Maru.

I disabled denoiser and tried increasing "Light Samples Multiplier" but still can't get a clean image. Even after 30 mins the whole image has artifacts and the light beam is not renderer as expected. If at some point you feel it'd would be a good idea to take a look a the scene by yourself, just let me know and I'll share it.

[mferster]

Have you tried a render test without the light's housing around it?

[Basshunter]

Have you tried a render test without the light's housing around it?

I have. But nothing improves apparently.

[burnin]

See if this helps...
Set Volume to "Single Bounce only" & make it's mapping "Step size" larger

PS
I found it somehow hard for Corona to clear noise (finding light in Volume) near its source

[PROH]

Hi. Just made a quick test with the sttings you provided as a starting point. I found this working:

Render settings:
Adapive Light Solver - OFF
Light Samples Multiplier - 8

Volume material settings:
Absorbtion Color - 128,128,128 (or lower)
Single bounce only - ON

The absorbtion color seems to be the single most important to reduce the noise.

Hope it helps

[Basshunter]

Thank you burnin and PROH for your suggestions. I tried using your settings but I'm afraid "Single Bounce Only" is not an option for me in this case. It reduces the scattering of light across the scene significantly, making everything too dark. My client and I need the lights to behave as close to reality as possible for this project.

On the other hand, I didn't see a great improvement in terms of noise reduction with any of the suggested settings. The renderer keeps having problems specially on the areas of the beam closer to the source. I guess these kind of effects like fog and steam are just difficult for renderers.

I'm a little worried at this point not knowing how I'll solve this issue. There're still another 41 moving heads to be added to the scene :c

[TomG]

Don't forget you can always send the scene to us via private uploader, see link in my signature, and we can take a look at your specific scene directly.

(BTW single bounce only usually makes the rays more prominent, and perhaps the loss of light across the scene as a whole could be compensated for by adding lighting that illumates the whole scene, just as a thought).

[PROH]

Hi. Hmmm.. before writing my previous post I actually made a direct comparison between your settings and my suggested settings, and found a noticeable improvement. So it seems theres something else thrown into the equation.

Besides that, I have done something like this before, using the standard Max light with "volume light" render effect for the beams only. That worked out quit well, with less noise and faster render times than Corona Volume Mtl. Maybe that's something to try out?

Regards

[Basshunter]

Thank you, Tom, for the tips. I'll prepare the scene and send it to the team. By the way, is there any benefit, at least in my case, from using a Volumetric Material on the Global Volume Material slot instead of a box or vise versa?

Hi. Hmmm.. before writing my previous post I actually made a direct comparison between your settings and my suggested settings, and found a noticeable improvement. So it seems theres something else thrown into the equation.

Maybe I missed something. There's a couple of mesh lights on the ceiling which I didn't mention because they're being rendered just fine. I'll take a closer look to the Max lights and see if I can get something from it.

[Basshunter]

Just revisiting my own post. I couldn't prepare and upload the scene before. I just did. Here's what I'm getting using Corona 7 and 3ds Max 2022. I really hope you guys can help me with this when you have some time.

[TomG]

Have you tried disabling Adaptivity?

[Basshunter]

Thanks for your quick reply Tom. By disabling "Adaptive Light Solve" the problem with the big chunks not being rendered correctly seems to be solved. This was not the case when using Corona 6 in my first posts, for some reason.

I'm still concerned about the amount of noise in the image. Is it normal?

On the other hand, Corona Render Help Desk says this about adaptive solver:
"The results produced with the adaptive solver enabled are always less biased (more realistic) than with the adaptive solver disabled."

In my case, how would not having this option enabled affect the realism of the scene? Would you mind elaborate a bit further?

[TomG]

Noise is expected as the calculations for volumetric lighting are more involved, so will take more passes (or heavier denoising) to clean up.

Shouldn't affect the realism here at all, that's more about light bouncing from HDRI env maps etc. so more like your conventional interiors. The adaptivity has a look to see "how intensely does this block of the image need to be rendered?" and then allocates processing power accordingly. The drawback can be, though, that if "not enough volumetrics" appear in a particular block, adaptivity decides it doesn't have that much hard work to do there so doesn't allocate as much processing power - this is why you see the squares in your image, those are the blocks that adaptivity divided the image into (as a future pointer for when disabling it may help :) ).

Hope that helps!

[maru]

@Basshunter - here are my recommendations:

option 1) Use 3ds Max native lights instead of Corona lights (if possible). Corona lights are more realistic, they always have some area, they have directionality, etc, but that makes them harder to render. 3ds Max lights are "fake" but they will render faster. I am not sure if it is possible to make 3ds Max lights have a visible disk shape rather than always being shot from a point, which may not work for you...

option 2) Disable Adaptive light solver in the Performance tab - looks like currently there is some issue here and this should be improved. The scene might render a bit slower but you will immediately get rid of the square artifacts.

option 3) Leave the Adaptive light solver enabled, enable the Development/experimental stuff rollout (this: https://coronarenderer.freshdesk.com/support/solutions/articles/12000021288 ), scroll down to "Lights" and change "Solver" from the default "Select automatically" to either "Better object-based" or "Scalable". Both seem to be working fine and without the square artifacts.

I would also advise increasing the Light Samples Multiplier to a higher value than the default 2 (probably ~4 will do the trick).

Attaching some example images and will send you scenes in PM.

[Basshunter]

Thanks for your help, Maru. Really appreciate you took the time to check the scene.

I'll probably go for option 2 or 3 since I need the most realistic result possible this time. Hopefully in the future we'll get faster rendering of volumetrics.

[Basshunter]

option 2) Disable Adaptive light solver in the Performance tab - looks like currently there is some issue here and this should be improved. The scene might render a bit slower but you will immediately get rid of the square artifacts.

option 3) Leave the Adaptive light solver enabled, enable the Development/experimental stuff rollout (this: https://coronarenderer.freshdesk.com/support/solutions/articles/12000021288 ), scroll down to "Lights" and change "Solver" from the default "Select automatically" to either "Better object-based" or "Scalable". Both seem to be working fine and without the square artifacts.

I would also advise increasing the Light Samples Multiplier to a higher value than the default 2 (probably ~4 will do the trick).

Attaching some example images and will send you scenes in PM.
[/quote]

Hi Maru.

Do you know what happened to the adaptive light solver you mentioned in option 2. I still have the same problem that lead me to create this thread.

[dj_buckley]

It was moved to the Development/Debug menu, which is hidden, so you have to unhide it through the Corona System Settings.  Then you'll get an addtional rollout on the Performance tab, where you'll find the Light Solver.  I'd also like to know why it was moved there but kept on by default?

[Basshunter]

I'd like to re-open this conversation since I'm experiencing this problem again. For some reason Corona seems to struggle when rendering lights with very narrow directionality in foggy scenarios. Specially the portion of the light beam that near the source. I've tried disabling adaptative Light Solver but the problem persists.

As you can see in image # 1, even after 10 mins the portions of the light beam near the source don't render. Image # 2 shows how even after using a very small region render, these portions have problems to be rendered completely.   

This is a big problem for us since as mentioned before, we do lot of stage rendering where moving heads and fog are the main thing. With this problem, even delivering some descent previews is almost impossible.

[Basshunter]

Even after almost 8 hours the engine seems to have problems rendering the image. Note how on many portions of the image, the light beams were not rendered correctly.

To make things even worse, look what happens when I turn Bloom and Glare On (3rd image)

[GeorgeK]

This is a tough one, the light beams should eventually clear out but it might take long depending on hardware. As for the bloom and glare issue it's quite sensitive under certain conditions and it can lead to that, we have it logged.

Regarding your case, I would personally fake it with corona light mtl & geometry, but someone might be able to give you a better alternative. I can send you a scene if you are interested in the fake solution.

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[Basshunter]

Hi George. I guess there's no better solution for now so I'll take a look at that fake version if you send it. Thanks for your help.

[GeorgeK]

Hi George. I guess there's no better solution for now so I'll take a look at that fake version if you send it. Thanks for your help.

I hope it can help you, granted quality wise is not that great but with a little tweaking and better masking (other than gradient ramp), you can pretty much have an optimal fake that renders relatively fast. Also do check lightmtl light emissions to see if you can further improve performance by disabling them.