wow this is so cool stuff.
how is the sim & render time?

I don't remember the render time but it was long. The fact was I didn't know how to optimize it ops:
There is no sim for this project. The clouds are created with vex volume shader and pointclouds ( 3 point clouds ) . Each point cloud storing radius and position info.

I've got time for a little update.
22 minutes with my 8 cores 3Ghz to render theses images.
I gave up point cloud and use i3d and sdf now : point cloud was to long to render I don't know why.

This render comes with a couple of questions :

First, I would like someone to explain me the “calcOpacSubNet” subnet of the basic smoke shader, especially the DpDz part … I took it from the Basic Smoke Shader and I would like to know exactly what happens here !
See the whatsthis.jpeg image.

I have an issue with the light global variable “L” ( direction from light to surface) when I try to make it works with volume shader. I can make it work easily with surface shader : I can get a Light Incidence Angle gradient making a dot product between “L” and “N”.
To get normal with volume I decided to use a sdf and a “gradient from file” node. The “incAngle.jpeg” is render this way.
But when I try with lights ( inside a Illuminance loop), I obtain the “backlight.jpeg” image.
The problem comes when I move the lights : the backlight image doesn't change
The same process with surface shading works fine …

thanks for your help

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Vincent

make a video tutorial on it . I will be grateful if you make a video lesson and will fill your Vimeo channel

I' ll think about it

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Wow! amazing quality! and thanks for sharing. Will love to deconstruct your files to learn the process.