Thanks for your answer and sorry for my delay!
There are not volumetric clouds (this is is something I’ll probably need to work on at a later stage, when I’ll integrate an environment “demo object” in DemoMaker) but only:
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High quality skybox
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Particle system used to generate the steam. This particle system is not the P3D standard one but a GPU particle system mainly based on the Flavio’s code (thanks to him!): example of shader-based particles by cflavio · Pull Request #476 · panda3d/panda3d · GitHub
I added some features on top on Flavio’s code: emitter shape, geometry shader, some rotating effect
on particle… (old code so I don’t remember right now all what was added but these are the main
features)
Of course, for particle systems, everything relies on base texture and parameters. For the base
texture, I simply use the standard P3D one provided in the SDK.
For the parameters, here is a view on the options used by DemoMaker:
- And the final touch is provided by the PostProcessing effects (PPE):
In the demo, I used a stack of 3 PPE: ACES, bloom and lens flare effects. Almost all the effects (and system) are based on the Technologicat system (thanks to him/her as well) - CommonFilters - some new filters, and the future - Panda Features in Development - Panda3D
I moved the code to GLSL and made some changes on it to fit my needs.
To put it in a nutshell: nothing highly advanced but a combination of nice features initially developped by community members 
Should you want a piece of code (from wezu) demonstrating procedurally generated clouds on a skydome, you can refer to: wezu/koparka: A heightmap and/or level editor for Panda3D (github.com)