Hi Basile,
Your observation is correct where volumetric clouds do not have collisions to be considered for LineTrace as they’re a cloud rendering system. That being said there are some things we can make use of to approach this problem as there is no equivalent built in.
An approach would be to sample the volumetric cloud material yourself. Here’s a discussion with a public example on how they did it. It describes the steps where you’d duplicate your cloud material that has a UVW coordinates parameter, create a 1px render target and make a dynamic material instance of your cloud material duplicate so you can change the UVW coordinates at runtime wherever you need to sample.
Another thing you could do, if you’re okay with approximates and clouds are mostly static, is to place an invisible collision component matching the volumetric cloud as a proxy but as mentioned it’s a vague approximate and may not visually line up well.
For additional information, here’s the documentation on the volumetric cloud component and a great video that deep dives into the volumetric cloud system. In addition to this, the volumetric cloud shader information can be found in VolumetricCloud.usf.
Please let me know if this information helps!
Regards