Trying to create a custom velocity field and hitting a brick wall

[eebling]

This could be a simple fix or a dumb question but I just started trying to learn houdini about 5 days ago so I'm lost and new to the package. I did the tutorial on the sidefx site with the volcano demonstration to show how to use the pyro tool preset and really liked how you could make a custom velocity field out of a box and converting it into a volume and doing some vex in the volume sop. So I wanted to experiment and try creating a custom vel field but out of a more interesting shaped volume. I made some sort of corkscrew looking geo and used an IsoOffset to create the volume but this is where the setup breaks. I know when I converted the box to a volume using the volume sop I changed the rank to a vector and I dont know how or where this option is when you convert a surface using the iso offset sop.?? When I middle click on the isoOffset, I see there is just one volume being output and when i middle click the volume sop it has 3 volumes listed. I Think this is where my problem is but again been using houdini a week and have no idea if this is the reason or not. When I plug the volume that is created by the volume Vop into the chain I get the nice curl noise showing up and when i swap it to the volume generated by the isoOffset then its just straight lines which would make sense i guess if it only is a scalar volume field. So Is there any way to convert the isoOffset volume to have a "rank" of vector.?? Or is there an entirely different/easier/correct way to make a custom velocity field that is a shape more complex than a simple box or sphere.? I'm trying to make the switch from Maya to Houdini but being a 13+ year user of maya it's VERY different from what Im use to working with. However the power in Houdini already is making me wish I made the switch a long time ago.! Thanks for any help/info..

E

[tjeeds]

Here you go,

A vector field isn't anything special, just 3 scalar fields named the same thing with .x/y/z tacked on the end. You can create them from a density field by plugging it into a merge 3 times and then renaming the fields. This setup uses the Volume from Attrib to sample in the tangent of the helix and visualise it.

volume_vel.hip

Edited July 23, 2013 by tjeeds

[eebling]

Ah cool, that worked. Doing the merging of the isoOffset 3 times onto itself and adding the name node in my setup made it do what I was hoping for. Thanks for the info