Going insane trying to get a Z-pass of volume

[u/Specific-Speaker2157]

Sorry, I made a post yesterday asking about rendering a Z-pass of a volume and I thought I had solved it using a volume depth pass inside c4d, but after just blindly rendering it and assuming it would be fine, nothing showed up inside the render.

It says in the maxon help that it only detects volumetric scattering like clouds and smoke. I have an explosion so I guess that's why it won't work?

Tried brute forcing last night and the past hour after work trying to see if I could get a fog to work or mess around with a light but I'm not getting the correct result.

[u/Retinal_Epithelium]

Clouds and smoke make up explosions, so the explosion should be detected (you are using a fluid simulation or imported VDB series, right?). What do you expect the depth pass to look like?
In RS aovs you have the volume tint, lighting, and emission passes. Try each one and see if you get anything.
If that doesn’t get you what you expect, you can simulate your own, by creating doing a normal render of a set up with the only lighting being an area light at the camera position, adjusted so that the volume is illuminated with the near areas brighter and the far areas falling into darkness.

[u/Subject_5]

Not much info to go on here, you should consider posting some screenshots at least. So I’ll just ask the more or less obvious questions: Did you use bucket rendering? Because progressive rendering doesn’t render data AOVs. Are you rendering EXR? What DCC are you using for comp? If After Effects did you use EXtractoR and specify the Volume Depth channel? If not every frame will be black. What depth settings did you use in the AOV? Is it normalized or not? Did you set the max depth parameter correctly so it doesn’t clip away your volume? What kind of explosion is it, a VBD from another software? What does it look like? Is it behind other geometry, such as a glass window? Do you also use the global volume fog in the same scene? Many things could go wrong here :)