Nice cloudy and animated 3D noise with VRay Environment Fog

[TubeSmokeGuy]

Hi!

Can you please give me an advice, how to get the best possible cloudy animated 3D noise, when using VRay Environment fog?

To be more specific I have some questions:

1. Which noise does work?
I tried VRayNoise, VRaySmoke, VRayBerconNoise

VRaySmoke - since this is name wise the first obvious option - it probably seems not to work, because it's not a 3D procedural? It looks weird when used as Density Map in VRayEnvironment fog.

VRayBercon Noise - when using this one it doesn't generate any noise in the fog at all? What am I doing wrong, some settings?

VRayNoise - This one seems to give at least a visible result in "3D" mode, but only with mapping set to environment and spherical (cube works too but looks weird). But then when animating the "time" parameter of the noise, it looks like the whole noise pattern moves as a big union instead of turbolent size changing noise cells, like usual. This also looks weird.


2. "Mapping" Type
Which mapping type, placement type etc. is the recommended one for maps used as density maps in EnvironmentFog? Default is Triplanar, but this seems not right for use in Environment Fog? Which one is the best here? UV, Projection, Environment? - And which settings should I use in the recommended mode?


It would be nice if you can help me a little.
Also a tutorial for this one would be very appreciated.


Thank you and gretings!

[viktor_angelov]

Hello TubeSmokeGuy Thank you for your questions. Please, share with us an image/video reference on what is that exactly you want to achieve.

Meanwhile, the main idea is to put a 3D map in the Fog Density slot so it affects the fog and make the gaps. If you want to animate it, you need to animate the texture itself. I understand it does not work for you. I can take a look if you prefer. Simply send over the scene and I will investigate further.

More about V-Ray Fog can be found here: https://docs.chaos.com/display/VRAYH...Ray+Fog+Effect

[TubeSmokeGuy]

Hey! Thanks for your response.
Meanwhile I got a useable result. I invested another couple of hours in parameter adjustments and setup changes. It was a trial and error story through the parameters and nodes jungle that come with VRay for Houdini. It was not funny. More like a blind flight. Unfortunately a lot of parameters are not well explained in the documentation, at least for my understanding. Also there are some example setups missing, in first place for a general "how to combine the nodes to get a working solution in the sense of their inventor" and in second place, a specific setup.
I cannot share my footage, it is confidential.

The main struggles are:

For the VRayNoise:
- Which "Mapping" type is the right one?
- Do I need to use the "UVWgen" input or is it enough to work with the parameters provided under the mapping tab?
- I want to stick my fog in place, so I cannot use Environment Mapping in "Spherical" or "Cube" mode, since now the fog moves with the camera when I have an animated camera.
- So I decided to create a "VRay World UV" node and plugged it into the "UVWgen" slot of "VRayNoise", because I want to stick my fog to the world (that was my consideration).
- Now, what to plug into the connectors of the "VRay World UV" inputs? Do I need to plug something in there? I was lost. So I blindly plugged a "VRay Transform Matrix" node into the "UVW Transform" input of "VRay World UV". I left all defalut parameters. I didn't know what I was doing, since I haven't found any documentation about this workflow.
- Now I needed to find a value for the "Frequency" parameter of "VRay Noise" that gives a visible result, regarding to the dimensions of my fog area. Unforunately there is no hint in the documentation in which relation "Frequency" stands to "Size in Scene Units" (which are meters by default in Houdini). So I started trying. I ended up with a value 4 , which gave some visible gaps in the fog. Finally. Until here it was no fun and frustrating as well.
- Since I now had a starting point to test render with visible feedback, I could start to create an advanced network of noises to give the fog billows a more natural and uneven cluttered look. That worked fine.
- Now, since I was doing an animation, I wanted to give the fog a slightly and slowly wobbling animation. So there is the "Time" parameter in "VRay Noise". But what does it do? The documentation about it is very worse. In which relation does the "time" parameter stands to "change of the noise pattern per frame" or "... per second"? So I started trying values. First one was $FF ... it was a fail, the noise changed a lot too fast. Even too fast to track with eyes. For a default this is a bad ratio.
- The next bad thing is, I need to render a sequence of multiple frames to see how the noise behaves over time. And this for every tweak I do, since there is no other way to get visible feedback. This is a very time consuming task.
- I tried multiple factors like $FF*0.03 to get closer to a smooth slow movement of the fog. Finally after a couple of test render squences, a lot of time and nerves, I got the desired result. But all over it was a nightmare to work.

For the VRay Environemnt Fog:
- 3 Parameters to control the visibility. Distance, Transparency and Density. Why? I needed to trial and error which input I have to feed or change to get the desired result?
- No good documentation about when to use which parameter.
- Also there is "height" but this one is at least - thanks to the lord - self-explanatory (cheers).


So please do more explaining in the documentation and more work examples in tutorials.

Thank you!