DS4.20 and volumetric

[Aelin]

A quote because it can help some people here. It's extracted from our February 2022 topic https://www.pfdlives.com/pfd/index.php?topic=8551.0

Not sure what's going on, but now I AM getting to see volumetrics in Iray preview mode!
That aside, a bit of info gleaned from the DAZ forums about the use of volumetrics!
Both cubes are the same. One on left is left at default, one on right of image is the 'twiddled one', the cube between them is the same primitive, but left as basic.
Each of the outside cubes has the same Iray volumetric shader applied, with the sane smoke.vdb attached.

If you check the parametrs of the Iray volumetric shader you will see an On/Off property called 'Clip to Geometry' which is On by default.

Note how the smoke effect on the left is cut-off ar where the boundaries of the cube it was applied to would be. Sadly this would also happen if you turned it to Off!
This parameter ONLY functions if the Material/Surface it is applied to is named 'Volume'. Notice that when you create a primitive that the only surface is named Default? Yeah, not that useful, huh?
This is where you gird your loins and jump into the Geometry Editor tool:
Select the primitive in the scene tab
Activate Geometry Editor (Tools> Geometry Editor or Alt-Shift-G)
Right-click the primitive, Geometry Assignmet> Create Surface ... (and give 'Volume' as name)
Select Geometry Selection> Select By> Surfaces> Default
Select Geometry Assignment> Assign To Surface> Volume
Exit Geometry Editor by slecting another Tool (probably Node Selection, Universal Tool or Surface Selector)
Making sure you have the primitive still selected go to Surfaces and select the Volume surface and apply the Iray Simple OpenVDB MDL Volume shader (find in: My Library\Shader Presets\Iray\Daz Volume) and then apply a VDB file to it.
Then select the Default surface and reduce Opacity Map to 0
The On or Off setting for Clip to Geometry will now function on the Volume surface.

[SimonJM]

Another, easier, way to do this is:
Create primitive
Select primitive
Select Geometry editor
Select Tool Settings (from Window> Panes (tabs) if not already visible)
Expand the Surfaces list and double-click on the name Default. This will enable you to enter a new name, so type: Volume.
Select your usual Tool to continue

[eblank99]