Hi, I want to get a particle Sim from Houdini into Maya. Alembic isn't an option because Maya's default importer is broken (only imports one frame). We're also having problems with FBX.

What would be great is to be able to convert the particles in Houdini to standard transforms, then to export this as a standard Alembic. To be clear, I don't want any geometry in the Alembic export, just a whole bunch of animated transforms- one for each particle. This would then be importable in Maya and would fit in with our existing pipeline quite easily to get what we need.

Can anyone tell me how I can use Houdini to turn a particle system into a transform hierarchy- one root transform, with an animated child transform for each particle? I'm a novice in Houdini so I have no idea if I can do this easily.

Thanks

Hi, if you can compile and want either a converter or plugins for maya, I wrote some open source tools based on disney's PartIO library a while back. I haven't been able to release compiled versions for a while, but they're still fully functional as long as you can run some fairly normal cmake builds.

https://github.com/redpawfx/partio/tree/redpawfx [github.com]

heres the “product page”

http://redpawfx.github.io/partio/ [redpawfx.github.io]

make sure you check out the “redpawfx” branch to get the maya and arnold plugins
otherwise, the main branch is just the original library with command line converters etc..

You can use partio in a bunch of ways, from command line conversion of .bhclassic files to maya .pdc for example, or using the maya plugins I wrote you can visualize the particles directly in Maya's viewport and
render them directly with an arnold render time procedrual that works with the visualizer.

There's also a cache reading “instancer” that you can plug into maya's particle instancer, which might be the closest thing to getting your “standard transforms” on geometry.. you can import the particles, instance locators to them and the bake out the instancer using any number of un-instancer scripts in maya to get keyframed geometry.


From a purely houdini standpoint, I believe you can copy-sop super simple geometry, onto your points.. give each a “name” attribute thats unique (in a wrangle s@name = “fooBar_”+@ptnum; )
then pack the geometry using “name” as the path

export this as alembic with “build heirarchy from attribute” on and set it to “path” and you should get your animated geo in a heirarchy..
you can just edit the “path” anyway you'd like to build the heirarchy up the way you want.

However the only way this is going to work is if you have a consistent point count.. no birth / death of points..

if you need / desire that sort of thing, you may have to either try the partio stuff i mentioned, or jump thru some more hoops to figure out your final count of the max number of points and deform them with some extra point ID type tracking.

hope this gives you some jumping off ideas.

-johnc