FEM - Missing velocity on EmbeddedGeometry

[j00ey]

Hi

 

I'm working on an FEM sim and I have some embedded geometry which is working fine, but when I import that back to SOPs, the v attribute is zero - it does have the attribute but it's zero. If I import Geometry instead of EmbeddedGeometry in the DOP Import SOP I get a proper velocity as well as all the attributes from the geo going into DOPS.

 

Is this normal or am I doing something wrong? I have Point Velocities set to Instantaneous but other settings make no difference anyway.

 

I can do attribute transfer or trail SOP but I just expected you'd get velocity for free.

 

Thanks for any info.

[ophamletsen]

Take a look at this topic: http://forums.odforce.net/topic/19513-fem-fracturing-with-embedded-object-velocity-attributes/

[j00ey]

Ah thanks very much, I didn't see that for some reason.

 

Is there a reason by the way that attribute transfer gives a more accurate result? I've just used a trail SOP for the moment as it seems faster.

[ophamletsen]

I think in the case of fracturing the Trail method might be less accurate, as it wont deal to well with changing point count.

With backward difference or central difference it wont be able to do accurate velocity calculations for those new points that appear where the fracturing takes place. 

 

For most cases though, I guess the Trail method would be good enough?

[j00ey]

Yes - that makes sense with fracturing. For my purposes trail SOP seems to be fine - though to get the same sort of motion blur as with the low res geometry I have to multiply the value by about 15 for some reason

 

Thanks for the input

[ophamletsen]

Just noticed this in the Journal:

 

"Tuesday, February 25, 2014 

Houdini 13.0.335: The finite element solver now creates a velocity point attribute on the embedded geometry."

[j00ey]

Oh great, thanks for the info. Time to download a new build!