Is it possible to modify several volumes inside a volume vop?

[magneto]

Hi,

I am trying to modify multiple volumes using a volume vop but I am not sure if I can modify more than 1? By default it always seem to modify density, right?

Do I have to modify a specific volume per volume vop and specify it explicitly in the parameters so the volume vop knows which volume to modify?

Thanks

[graham]

You need to bring additional volume primitives in using parameters. For example, to modify the vel prims you can create a Vector parameter named "vel" and the VOP will bind it to the named prims and allow you to modify them. You also need to have a copy of the same parameter set up to export in order to send the values out.

[magneto]

Thanks Graham, that helps alot. Btw if you had 2 volumes with 2 different resolutions, would that be a problem to modify them in a volume vop? I imagine when you are getting P from the Global parameters, it won't perfectly match the voxel positions of the other?

I don't have this kind of issue, but just wondering

[Annon]

It's a good idea to keep your volumes the same resolution.

[tjeeds]

Differing resolutions won't cause any problems as far as the Volume Vop is concerned, running a noise from P for instance, you'll get roughly matching values at different resolutions (with the exception of aliasing). rand(P) is the only thing I can think of that would not more or less match up.

[magneto]

Thanks guys. Jesse, that makes sense. I was thinking that volume vop iterates through voxels similar to vopsop iterating through points. So that's why was wondering if it would throw it when it's trying to iterate through voxels in volumes with different resolutions.

[tjeeds]

Well it does, but I'm pretty sure it treats every voxel of every volume as an iteration. If you have 2 matching volumes that's twice the iterations, each volume is not going to be running the same ops anyway. I use down-res'd rest fields all the time, no problemo!

[magneto]

Thanks Jesse, I see what you mean. Somehow I was thinking it tries to loop each matching voxel at once. So if you had 3 matching volumes, it would be 1 iteration regardless.

So then that's why you can specify which volume to bind to the volume vop so you don't waste iterations on other volumes, right?

[tjeeds]

Correctlingsworth!

[magneto]

Thanks Jesse, I am still trying to wrap my head around volumes so it takes a while