[Sidefx-houdini-list] advect along surface

Gary Jaeger gary at corestudio.com
Sun Sep 11 20:25:44 EDT 2016


Thanks guys. I’ll take a look and see if we can sort it out. We’re basically combining https://www.sidefx.com/tutorials/curl-noise-flow/ <https://www.sidefx.com/tutorials/curl-noise-flow/> and https://www.sidefx.com/tutorials/houdini-boolean-volume-denting/ <https://www.sidefx.com/tutorials/houdini-boolean-volume-denting/> but having our points (and trails) slide out of the intersection cavities i.e when the poly mesh breaks the surface we want to allow the points to come out and flow along the surface. Fun problem to solve. 

Gary Jaeger / 650.728.7957 direct / 415.518.1419 mobile
http://corestudio.com <http://corestudio.com/>
> On Sep 11, 2016, at 3:54 PM, Olex P <hoknamahn at gmail.com> wrote:
> 
> Hi Gary,
> 
> If I understand you correct, I would sample velocity from a volume, then
> transform it into a tangent (uv / whatever) space of the "mesh", find new
> position in the same space and finally transform that position from uv /
> tangent space into 3d space.
> How exactly you do that is another question. It really depends what are you
> after.
> Another method would be computing position as p' = p + dv, where dv is
> velocity per frame and then doing correction of that new position p' by
> volume gradient (i.e. pushing position along the normal to the surface).
> This one is fully 3d, but you need a wide enough band in the volume.
> 
> On Sun, Sep 11, 2016 at 11:17 PM, Gary Jaeger <gary at corestudio.com> wrote:
> 
>> Hello. We’ve been experimenting with advecting points in VDB volumes.
>> Cool, but is it possible to do something similar but only along the surface
>> of a poly mesh, instead of inside the whole volume?
>> 
>> Gary Jaeger / 650.728.7957 direct / 415.518.1419 mobile
>> http://corestudio.com <http://corestudio.com/>
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