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

Nicolas Delbecq nico.delbecq at gmail.com
Mon Dec 10 05:18:44 EST 2012


Actually you're right. It didn't work. The velocity inheritance was making
it looking like it was colliding but wasn't...
I guess I'll have to invert sdfs for fluid sims then...

Cheers,
Nico

On Wed, Dec 5, 2012 at 9:55 PM, Vincent Fortin <vfortin at gmail.com> wrote:

> I'm surprised you've managed to use a normal sdf for collisions though. For
> me it doesn't work. It all boils down to how the rig is built, collision
> detection shares nodes with sourcing which relies on positive values to
> generate the mask. Surely there are other reasons. I'd like to know too!
>
>
>
> On Wed, Dec 5, 2012 at 2:00 AM, Nicolas Delbecq <nico.delbecq at gmail.com
> >wrote:
>
> > 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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