Simple question: I've cached a few pyro sims in separate scenes, and I'm now merging them together into one larger scene, primarily using the DOP I/o node.

During the caching process, my pyro smoke has been saved out as the standard “density” field, which is great. But in the scene where all the pyro sims are merged, I'd like to have each of the caches load their data into a separate field other than density which I can then use to apply a unique shader.

In other words, I'd like to rename the density field from one cache to “cloud” and apply a white fluffy shader to it, rename the density field from another cache to “dust” and apply a brownish shader to it, and rename the density field from a third cache to “inky smoke” and apply a dark black shader to it.

I'd specifically like to do this renaming work during the cache loading process, rather than during the sim (mostly due to my workflow).

This must be something that's very simple to do (probably using a volume vop), but I can't figure out how. I'm probably missing a checkbox somewhere. Thoughts? Thanks!

Luke

you can use Name SOP to rename or name primitives (therefore volumes as well)

to assign different shader you don't have to rename anything (if you do it would just be more complicated as you would need to use that name in the shader to get desired volume)

if you are merging the volumes into single geometry, then you can assign material using Material SOP either to each one before Merge SOP (or even after by specifying directly primitive number in material group for each of them)

but you can as well import each sim into different object therefore just assign separate materials to those objects

Thanks for the reply.

After testing it out, I'm able assign a material to each of the caches, and render them out separately before the merge. But if I try to render them both out together after the merge node, only one cache/material/channel is rendered out, and the other is ignored (even though both appear in the viewport).

EDIT: Once I used a Volume Merge SOP instead of a standard Merge, I was able to successfully render the two together, but only using one material, not two materials.

I'd like to try out the Name node as you had described to change the field names, but I'm not able to get it setup correctly for that purpose; the Houdini help files tell me to “See Attrib String Edit for more information”, but that page doesn't help me out that much - as I'm not sure of exactly where to type in the “from” and “to”, etc.

Luke Letellier
…
I'd like to try out the Name node as you had described to change the field names, but I'm not able to get it setup correctly for that purpose; the Houdini help files tell me to “See Attrib String Edit for more information”, but that page doesn't help me out that much - as I'm not sure of exactly where to type in the “from” and “to”, etc.

as all your volumes are called “density”, from/to isn't going to help you

middle click oh your merge node and you'll see which prim numbers correspond to your density primitives
then in Name SOP
type them one by one to Group/Name fields, like
Group: 0
Name: cloud
+
Group:1
Name: dust
…

but as I said, you can burn yourself going this way as in the shader you need to call volume by it's name

Why don't you try separate object per your volume sim?

tamte
Why don't you try separate object per your volume sim?

Oh wow. Duh. For some reason my mind was locked into the idea that they all had to be within the same node. But this is much easier. Thanks!