[Sidefx-houdini-list] volume vex context in houdini

jlait at sidefx.com jlait at sidefx.com
Tue Aug 26 11:32:38 EDT 2008

On Fri, Aug 01, 2008 at 02:55:52PM -0700, Lucio Flores wrote:
> I'm having trouble finding some functionality. I want to compute the
> gradient of a level set volume. I know there is a volumegradient vex
> command, so it should be a rather simple matter of calling
> volumegradient from the volume vop, correct?? But the only version
> of the volumegradient vex command available in the volume vex
> context is one that loads the volume from disk. 
> For that matter, is there a way to get the volume density of
> neighboring voxels in the volume vex context?? How can I get that,
> so maybe I can compute the gradient myself??

    The Volume Vop contexts aren't normal geometry contexts so only
have the file method.  However, things are not as dark as they seem.
Anywhere you have a file input you can use the op: syntax to refer to
a live SOP in your scene.
    1) Use Volume Gradient From File
    2) Create a parmeter from the file name
    3) Set the parameter to

    If you want to expose it to a user as a SOP chooser,
    4) Collapse Volume VOP into a subnetwork
    5) In that subnetwork, add an Object Merge.  Export the object
merge's SOP path to the subnetworks parameters.
    6) Set the parameter on the Volume VOP to 

    The fullpath is requried as the op: syntax needs full paths as by
the time it is evaluated the local node path has been lost.
    You can look at the Advect By Volume POP for an example of how
this can be set up.
        - Jeff Lait

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