Hi
I am trying to get this progressive (or any caustic) calculation into a night project and I am getting weird at least for me results. The lights are 2 instanced disc. I am not sure why I am seeing this shadow around one of the light (I have also tried to delete this one and replace it with other but same result.I have played with search distance to get some sharp shadow but this is as much as I can get. Photon maps the same.
Is there any more info needed to make it work properly? Or it is how vray caustic works in those condition and there is nothing can be done?
I think you will need to post the scene in order to work out what is going on.
It’s quite hard to work out without it 
Sure, scene attached
Caustic_pool.zip (598 KB)
Ok, so if I delete the light that causes the issue in your scene, then the other light has the same problem, which is weird.
I am running Vray 6 beta, so maybe that is the issue. I’ll try again tomorrow, unless somebody else confirms or otherwise.
I am on v5 and this is the same behavior. If I play with directional parameter I can make it go away but I agree there is something off and should not behave like this. Or maybe I am missing something.
Sent it to support to see if they can come up with solution for this problem and will post the findings.
@urbanite Just so you know, we’re investigating the issue.
Thank you Aleksandar!
I noticed that although they are instanced lights, in Vray Properties one has a caustics multiplier of 5 and the other just 1, which
is why you didn’t notice it occurring on the other light. Same with caustics subdivs, they are not instanced, so different.
It also happens with any other shape of light.
I changed the water shader to a simple one with ‘affect shadows’ turned on, just to test.
With caustics off it renders as expected, though with caustics on, even though affect shadows is ‘on’ it still creates those artifacts, which I wasn’t expecting.
Also, even when the lights are set to not cast shadows the same thing occurs.
It might be, I was playing with the settings to see how they impact the caustic, so I might break the instances. As far I remember even changing the light type to square were resulting with the same sphere-ish band.
It’s all weird, so I couldn’t draw any conclusions other than it seems broken. I’m sure they’ll figure it out
I took it all the way back to Vray Next (wow…so slow LOL) and it’s the same with that.
Yeah, it looks like it’s a deep-rooted issue with the old non-progressive caustic photon map.
Definitely Devs’ territory, thanks for the file!
Ok, I really was hoping that I have made some mistakes with the setup and you just give be brilliant solution for this issue as I would have a good use of caustic in current project. Even though it would be fixed at some point I am afraid that it will not be very helpful for as I am still on vray 5.13. Further updates were broken with my windows7 which is not supported by chaosgroup anymore. As vray 6 is on the horizon I will update the system when I have a bit more gap between the project. I am a little bit surprised that nobody tried this caustic setup before but if there is any workaround please let me know. Thank you!
What appears to work is a directional setting of minimum 0.7, which aesthetically you might find useable
Yes, as I mentioned I was able to get “fix” by changing directional parameter but I am interesting in cleanish more accurate caustic on walls. I can rerender pool twice where second would be “fixed” (by direction parameter) caustic pool.
Mind if you point me to the scene so I can download it?
https://support.chaos.com/hc/en-us/articles/4406557515281-How-to-make-refractive-caustics-water
Vray sun of and just add light into water, Aleksander.
Okay. This seems like something specific to caustics in volumes. The dark halo seems to correspond to the diffuse lit area. I tried recreating the effect in Corona, and there it seems to behave as expected (with the special “caustics in volume” option).
I found a weird workaround - by enclosing the submerged light in a “water sphere”, the caustics appear again. Check the attached scene. Render with and without the water sphere, and you’ll see the difference.
vray_caustics.7z (98.2 KB)