Hey guys! i'll keep it succinct.
i'm trying to advect some particles via a VDB I've imported from Embergen.

I've imported a VDB with the purpose of having it advect some particles I've made from my pop network it looks like this


, and it has THESE attributes.


As you can see, it has velocity in the x y and z. However in the Advect by volume node in my pop network.
The field name for the source is just Vel


So that makes me wonder, do I need to tell Houdini that the velocity's I've brought in, are assigned to vel? if so. How do I do that?

In this case, it's just asking what the field is called in your source so just use velocity as it's called in your volume.

First, though, the velocity field names don't appear to be in the typical format for Houdini - you'll probably want to use a name SOP to rename the volumes, substituting periods in place of the underscore (or change it to vel.x etc and then leave the parameter in popadvectbyvolumes at default)

nice 1. April post...
for all others: floattovec in an attribvop

VDB vector merge.

hey guys! Just wanted to thank you for the help! I wasnt able to get back to this at the time, But again. Thank you.

hey man - sorry to necro this post - maybe you already figured it out

the embergen co-sys is a real pain in the ass

first you need to convert the embergen volume - convertvdb set to 32bit float

followed by a volume wrangle to re-orient the scalar vectors within the sim to work with Houdini's:

float vx = f@velocity_x;
float vy = f@velocity_y;
float vz = f@velocity_z;

// EmberGen Z-up → Houdini Y-up (right-handed)
f@velocity_x = vx;
f@velocity_y = vz; // Z becomes Y
f@velocity_z = -vy; // Y becomes -Z to keep handedness

then i used a vdbvectormerge to combine all the scalars into a "vel" attrib

from here, it should just work