[Sidefx-houdini-list] Fluid Source Sop creating inverted levelsets

Nicolas Delbecq nico.delbecq at gmail.com
Wed Dec 5 05:00:16 EST 2012


I understand that. If you invert the levelset from the fluid source sop (so
you have a normal one) you can still use it as a collision in dops as long
as your source volume dop has its source volume parm set to minimum,
instead of the default maximum.

What I don't get is why sideFx has chosen to use inverted levelsets by
default where actually they could have set it to use normal levelsets. I
would be curious to know the reason...

On Wed, Dec 5, 2012 at 8:35 AM, Vincent Fortin <vfortin at gmail.com> wrote:

> If you go in the Container Settings tab and switch between the different
> modes, you'll notice that the volumes settings change. Source Smoke will
> generate a simple volume, Source Flip will generate a SDF, whereas
> Collision will generate an inverted SDF by automatically UNCHECKING the
> invert option for you. Don't worry, you're a sane person in an insane
> world.
> At least the documentation has 1 mention about it:
> "Some fluid operations (such as collisions) expect negative border
> conditions to work properly."
> Now that it all makes sense, you can go and vop-negate the values inside
> the volume and effectively reuse your SDF's for other things. As long as
> you take care of the name bindings... but that's a different story I guess
> :-)
>
>
>
>
> On Thu, Nov 29, 2012 at 9:19 AM, jacob clark <jclark2900 at gmail.com> wrote:
>
> > Hey Nico,
> >
> >  It is quite strange! Luckily we've managed to work around the
> strangeness
> > so far in our pipe. But if anyone knows, I also would love to know what
> the
> > benefit is for inverted level sets.
> >
> > cheers,
> > -j
> >
> >
> >
> > On Thu, Nov 29, 2012 at 9:08 AM, Nicolas Delbecq <nico.delbecq at gmail.com
> > >wrote:
> >
> > > Hi,
> > >
> > > I've noticed that the fluid source sop was creating collision levelsets
> > > being positive inside the volume and negative outside. By default the
> dop
> > > source node is reading that correctly.
> > >
> > > This is an issue because when your pipe relies on levelset for other
> > > operations you can't use directly the ones created from the fluid
> source
> > > sop.
> > >
> > > Do anyone knows what's the reason for that ? Seems quite strange no ?
> > >
> > >
> > > Cheers,
> > > Nico
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