Transfer Volume attributes to Mesh/Points/Prims

[chrisdunham95]

Hey guys I know this may already have been asked somewhere, but had a real good luck and couldn't find much so my apologies if so! 

So I have a mesh generated from a volume (convert vdb > convert vdb to polygons) but my (density/temperature/vel etc) attributes get carried over in prim attributes from looking at my geo spreadsheet. 

I was trying to promote the attributes across so I can then use them to color my mesh, but so far been unsuccessful,

if anyone could explain how I would do this and how it works that would be great! 

 

 

[StepbyStepVFX]

Hi Chris,

I don't really understand what you have in your scene : seems you had different VDB (one for each field you mention : density, temp, vel etc.), then you converted one of them to poly using the Convert VDB ? Each field is considered as a primitive, but once you transform them to Poly, you loose the info that were stored in each voxels.

So if you want to sample your VDB close to the points of your poly to transfer attributes, I think the easiest way is to do it through a point VOP, where you wire your geo in input 1, you wire your VDB in input 2 and use a "volume sample" or "volume sample vector" node (maybe you need to convert your VDB into a houdini volume, not sure, don't remember...).

Hope this helps ?

[chrisdunham95]

13 hours ago, StepbyStepVFX said:

Hi Chris,

I don't really understand what you have in your scene : seems you had different VDB (one for each field you mention : density, temp, vel etc.), then you converted one of them to poly using the Convert VDB ? Each field is considered as a primitive, but once you transform them to Poly, you loose the info that were stored in each voxels.

So if you want to sample your VDB close to the points of your poly to transfer attributes, I think the easiest way is to do it through a point VOP, where you wire your geo in input 1, you wire your VDB in input 2 and use a "volume sample" or "volume sample vector" node (maybe you need to convert your VDB into a houdini volume, not sure, don't remember...).

Hope this helps ?

Thanks Jo, that makes way more sense now can see where I'm going wrong! 

[jeannel]

attribfromvolume does that.

[ftaswin]

@density = volumesample(1, "density", @P);

v@v = volumesamplev(1, "vel", @P);

[loucifer]

Could you post your result, I'm currently trying to copy color info from vdb to geo and it seems you resolved it?