Not sure if I should ask this inside the vray forum or this one but oh well 
I’m currently trying to use the krakatoa atmospheric effect to “fake” some reflections/refraction of a krakatoa sim. The only problem I have I’d like to make the voxels invisible to camera so I really get just the reflections/refractions. But it seems that krakatoa or vray ignores the “visible to camera” checkbox. Is this a general limitation or infact a vray problem?
Cheers,
Ralph
I am not sure whose problem it is, I am not even sure it IS a problem (it is clearly an issue for your workflow, but it could be As Designed).
The right question to ask is “What does the Max Scanline Renderer do in this case?”
If you create a Sphere Gizmo helper and assign a Volume Fog to it, you will notice that the Sphere Gizmo does not even expose those options in the Object Properties dialog, which leads me to believe Max was never designed to support that sort of visibility in its renderers.
In fact, historically speaking, the Visible To Camera option came from the mental ray implementation efforts. Of course, mental ray is the only renderer that is not supported by Krakatoa Atmospherics. But what I am trying to say is that the problem might be related to original design decisions when the Max atmospherics were first developed. But I could be wrong.
I cannot test with VRay on my laptop right now, but it would not hurt testing whether VRay lets you somehow do what you asked with other Atmospherics like the Max ones, or FumeFX. If there is a precedent where this approach is actually supported, we might have to look into making it possible with the Krakatoa Atmospheric effect, too.
Hi Bobo,
I just tested the same approach with just a random fume sim. And fumefx + vray works with the visible to camera option. I did a quick test scene with a reflective ground plane and a glas box on the left side. You can see the smoke though the glass and in the reflection.
I’m asking because I was approached for a small perfume ad where the flacon is in perfect darkness at first and is approached by one of those wispy krakatoa thingis we all know flies around it and does it’s thing. So the client would love some reflection/refraction on the bottle. The atmospheric approach was the first that popped into my mind. Guess I have to think of something else.
Thanks for testing Fume and VRay, I will log this and we will see if it is somehow easy to add.
Have you tried rendering a VRayReflection Render Element to try and isolate just the reflection without the actual Krakatoa Atmospheric in camera?
You could then composite the reflection pass over your VRay rendering with the Krakatoa Atmospheric disabled.
Didn’t test that yet. Sadly I’m not in front of my workstation at the moment. But in theory this would still make problems in situations where the voxels are in front of the object. And in addition rendering the unwanted parts of the atmospheric effect would add to the rendertime for the animation. + I would have to render the sequence two times. Will still do some tests tomorrow.
Thanks for the help Bobo and adding my “request” to the wanted feature list 
Guess I was wrong the vray reflection pass seems to ignore the smoke. So rendering the whole sequence two times would be an option. Since the atmospheric effect needs a krakatoa render license to work is it supported by distributed rendering inside vray?
I haven’t used it in production, so I don’t know how exactly it will behave. I would expect each machine launching VRay to attempt to acquire a license. I don’t think Krakatoa would see a difference between regular network rendering and VRay DBR. What behavior would you expect?
Also note that we offer rental of all our licenses on a weekly basis if you need to increase your render power for a few days…
The empty bucket syndrome I had that once with fume fx that the joined machines wouldn’t load the sim data. So I had “holes” in my render. Is there any way you guys could test if DR works before I decide to if I want to rental option.
I am at home in Europe on a prolonged visit to my parents. I am working remotely on my laptop and have no way to test anything. 
I can ask our guys in Winnipeg to see if they can test it, but I believe it is better if you test it yourself since you know exactly the setup that is expected.
We can cut you a temp. license for as many render nodes as you need for a day or two. If it works, you can make a decisions…
I’m not back in the office before Monday but one test license for a day would be more than sufficient and generous.