motion blur from openVDB Mesh to alembic

[redpaw]

I've got a particle sim I'm meshing with openVDB,

I would like to export this with motion blur to an alembic cache to render in maya/arnold.

simple example, not using particles, but yeilding the same results..

make a torus, and add rotation animation xform node.

convert to VDB using vdbFromPolygon

convert back to polygons with convertVDB node.

add a trail sop to compute velocity.

export using alembic rop.

If I skip the convert to vdb and back and just export the rotating torus, I get subframe motion

based on vertex velocity in the alembic file without exporting extra motion blur steps in the alembic file... however with the openVDB stuff I end up with static geo inbetween frames. even though it seems to be creating proper vertex velocity.

I can export this as a realflow mesh and it will pass the velocitiy correctly so is this a problem with the houdini alembic exporter? or user error on my part?

I'm writing out 20+ mil poly meshes so I'd rather not have to subsample them and write out the data 2-3x just to get motion blur.. at that point I might as well go back to realflow meshes instead.

any help would be appreciated.

thanks in advance

-johnc

redpawfx