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sebkaine

Speed Stretching with VDB ?

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Hi Guys ,

 

i would like to know how to stretch my vdb mesh by injecting a velocity field.

i would like to mimic the RealFlow deformation effects or the particle fluid node in H.

http://support.nextlimit.com/display/rf2014docs/PML+-+Deformation

 

I have try to use the VDB advect node but without success ...

 

An older post say it was not possible, is it true for H14 ?

http://forums.odforce.net/topic/19730-is-particle-fluid-surface-sop-not-used-anymore/?hl=%2Bvdb+%2Bspeed+%2Bstretching

 

I would also like to know if anisotropic meshing is possible in houdini ?

 

Thanks for your time !

 

Cheers

 

E

Edited by sebkaine

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With the VDB From Particles SOP you can turn on Velocity Trails. No anisotropic meshing yet as far as I know.

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Thanks for your help David !

 

The problem is that i need both :

- Particle Blending

- Particle stretching

 

Both are working with the old particle fluid mesher.

But i am unable to get the same behavior with VDB.

 

Speed stretching is really one of the key element for realistic liquid.

Having this in VDB would be cool ...

 

I give you a simle exemple to describe my problem. you will see that you can only have stretch OR blend in vdb but not both !

 

 

mesh.hip

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Hey dude, does this help at all? 

 

Couple of values to play with to get it more like the original but it looks close to me, using point replicate to get the velocity stretch and pc lerp to blend it and stop the point replicate noise youd normally get.

mesh_wrangle.hip

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Thanks for the tricks Aleksandr ! it's simple and clever ...

 

I think that a simple wrangle that add points at @P-normalize(@v) with a decresaing @pscale could do exactly what i want ! 

 

Nice avatar from The Holy Montain ... by the way :)

Edited by sebkaine
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did you tried vdb masking? calculate the length of the vel field with a vdb analysis and use that scalar field with the gradient to dialate/ erode the sdf.

wont give you the stretching tho..

 

one should calculate the orientation and stretch the scale by velocity. with scale I dont mean pscale but a vector attribute, which describes the non uniform scaling of the point according to the direction and magnitude of the particle.

this basically results in a transform.

but Ive got no clue how to modify the surface sdf with that...for now.

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Thanks a lot Sebastian ! Very cool ideas i'm gonna dig this !

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