Advect by Volumes

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Can you use the “Advect by Volumes” with a sim or bgeo file instead of a live sim?

If so, a little help as to how.
Thanks
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Sure. The slow-but-easy way is just to use a File SOP to read in the .bgeo sequence and then point the AdvectByVolumes at it.

The fast-but-slightly-more-complicated way is to unlock the AdvectByVolumes asset (right-click and “Allow Editing of Contents”), figure out which of the advect_by VOP SOPs you're using and set the VelocityFile parameter directly to your .bgeo sequence.

Edit: I should add, if I don't mind using a lot of memory, sometimes I'll use option 1 above and follow the File SOP with a Cache SOP and it starts to get pretty quick again. Or load the .sim file back into a DOPNet and use the built-in caching there.
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oh duh!! See I thought of that but for whatever reason I wanted to point it directly to a disk file instead of to a File SOP.
Genius! Thanks!!
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You must be careful that your target SOP either only contains ONLY the 3 velocity volumes, or in the AdvectByVolumes POP, place a: @name=vel.*
Jason Iversen, Technology Supervisor & FX Pipeline/R+D Lead @ Weta FX
also, http://www.odforce.net [www.odforce.net]
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I got it working with a dummy bgeo file at home but I still cant get it to work with my sim file.

The example the help gives for a live dopnet is similar to - “/obj/dopnet1:smokeobject1/vel”

So i've tried every combo of that I can think of, to get my AdvectbyVolume to work with my sim file. I've tried a file SOP with the object masks and data path set, and I've tried it with * in them and still cant get it to work.

Any help?
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Well, there's a couple of ways of doing this with a .sim file. The syntax you're using for the live DOP sim is useful if you load your sim file into a new DOPNet, which is not necessarily a bad way to go at first, although you might end up loading more data than you need.

So, in that case, create an empty DOPNet, put down a File DOP set to “Read Files” and point at your sim sequence. Open up a Details View and make sure all your data is being loaded and double-check the names of everything. Then you should be able to use a similar syntax as in the help file to access the velocity field. Upside is you get automatic caching by default, downside is you're probably loading in more data than you need.

To use a File SOP, you should be able to point it at the .sim sequence directly, but the important field here is the Geometry Data Path, assuming there's only one DOP object in your original sim. In that case you should be able to leave the Object Mask set to “*” and set the Geometry Data Path to “vel” to get the velocity field. (You might try “density” as a sanity test, and right click on the node to make sure it's loading what you think.) Then point the AdvectByVolumes at the File SOP (or a Cache SOP if you want caching).
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I submitted an RFE this morning to allow the advect by volume pop to access .bgeos
Stephen Tucker
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Dopnet trick worked like a charm! Thanks

I have to say there's a serious update/cache issue with the AdvectbyVolume POP. Even with the correct path I had to copy and paste the entire node before it would work.

Thanks so much Johner and Allegro!
“In the beginning the Universe was created. This has made a lot of people very angry and has been widely regarded as a bad move.” - Douglas Adams
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