vdb advect

[koen]

Hey guys, 

I often want to advect a fog volume, just to deform it by a vector field basically. I always forget vdb advect only supports sdf's ( and converting back and forth seem to give me funny results). Would it be hard to add support for fog fields in the advection tool?

Cheers,

Koen

[Chris Rydalch]

In OpenVDB 3.1 added support for advecting arbitrary volumes; if you build the Houdini SOPs, you should get the new OpenVDB Advect SOP.

http://www.openvdb.org/documentation/doxygen/changes.html

[Jeff Budsberg]

yeah advecting level sets, scalar fields and points are all supported as of 3.1.  on a related note, we also recently added a tool to take any velocity grid and make it divergence-free.

(see attachments)

[koen]

Cool, I'll take a look, thanks guys,

Koen

[Daniel Elliott Jones]

are there any example setups for the 'remove divergence'. I built the houdini sops a while ago and tried it out but it didnt seem to be doing anything. i assumed i had set it up wrong.

it seems thats its possible to build a proper fluid solver with it.

[Jeff Budsberg]

i've attached an example hip for you; it takes a velocity noise, removes divergence, then advects points through it.  

let me know if you have questions.

-jeff

[Daniel Elliott Jones]

Hi Jeff, I misplaced the original file and the attached file doesn't seem to exist on the google servers anymore. Any chance you could re-upload it please?

Cheers

Dan

[Jeff Budsberg]

it's been a while, but i think it was this one?

[Daniel Elliott Jones]

Thats the one yeah thanks

I've actually been setting up a smoke solver setup using the remove divergence. It works apart from the process of padding tiles is really tricky. simply expanding isn't the best solution as it continually expands. What is needed is a padding node that pads a number of leaf nodes around the edge only if it contains values in the node. It would also take care of pruning automatically. Just need to find a way to do it.