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juncho

How do I import vel from another DOP?

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I'm trying to extract a velocity from one cached vdb to use it as incoming vel in another DOP.

In DOP I/O,  I've imported velocity as vel and it seems like it's cached as vel.x, vel.y, vel.z. (scalar field perhaps?)

and Houdini documentation claims that volume source can handle these separate three fields as one single vector field (vel) but it doesn't work.

 

I'm trying to bring it to another DOP using volume source SOP just to import the velocity.

I've tried changing field ranks in all of the following methods.

Source volume         Target field 

    vel                           vel

    vel.*                        vel

   vel.x                         vel (tried changing vel.y vel.z as source vol)

    vel.x                         vel.x (tried changing vel.y vel.z on both source and target)

 

1.thumb.png.63ca2cef0379ea21f341a88a069b9fb1.png

vel import is checked and attribute shows that it is saved as vel.x,y,z

 

 

3.thumb.png.2c234101650a65c2cd72d2e1a5a42a07.png

destination DOP. Import SOP path is correct and density is also imported while velocity is not

 

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Posted (edited)

you can  convert them to VDB and then use VDB Vector Merge SOP to get a single vector volume, that one should work

 

also according to help for Source Volume parameter:

Quote

  Name of the SOP volume or VDB to merge. For vector fields, this can be a single vector VDB or a space separated list of three scalar volumes or VBDs.

so for scalar volumes that would mean list of all 3, not just one of them: vel.x vel.y vel.z

Edited by anim
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18 minutes ago, anim said:

you can  convert them to VDB and then use VDB Vector Merge SOP to get a single vector volume, that one should work

 

also according to help for Source Volume parameter:

so for scalar volumes that would mean list of all 3, not just one of them: vel.x vel.y vel.z

Ah nice catch! I haven't used the new sourcing system that much and didn't know about this. In the old Source Volume DOP you could use only "vel" fine even if it was consisting of .xyz scalar volumes. With the new Volume Source DOP however, it is as you describe.

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23 minutes ago, anim said:

you can  convert them to VDB and then use VDB Vector Merge SOP to get a single vector volume, that one should work

 

also according to help for Source Volume parameter:

so for scalar volumes that would mean list of all 3, not just one of them: vel.x vel.y vel.z

 

Yes! I should have read more carefully. Thank you so much. This solved my problem :)

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