[Sidefx-houdini-list] particle birthing query

Andrew Lyons tstexture at gmail.com
Fri Jan 27 15:02:34 EST 2012


Somewhat related is the need to the interpolate the point position of
cached emitters between the current frame and next (or previous) frame.
You'll need a SOP otl that contains two files SOPs (to read geom at $F and
$F+1) and a BlendShapes SOP to get good subframe position values. Without
this it won't matter what oversampling you have set on POPs. (You also
won't get some motion blur variants for some renderers.) Keep in mind that
$F ticks over to the next frame at $F + 0.5  - so you need to read geometry
at floor($FF) and blend from current to next with frac($FF).

Cheers


On 27 January 2012 11:38, Spencer Lueders <spencerlueders at gmail.com> wrote:

> Hey Phil,
>
> One way to avoid using oversampling to get particles in between is to
> create a timeshift SOP and set it to $F - 1, after that create a vector
> attribute in SOPs and call it 'prevP' and assign the pt position ($TX, $TY,
> $TZ).  Attribute Copy 'prevP' back onto your orig geo.
>
> In pops, create a birth group, 'justborn', followed by a position POP.  In
> the position pop, assign the 'justborn' group.  In the Postion parameter,
> replace $TX, $TY, $TZ with fit01(rand($ID + 2426), $TX, poppointid($ID,
> "prevP", 0)), fit01(rand($ID + 9856), $TY, poppointid($ID, "prevP", 1)),
> fit01(rand($ID + 3526), $TZ, poppointid($ID, "prevP", 2))
>
> This will randomly put the particle somewhere between the current frame of
> the emitter and the previous frame of the emitter.
>
> Hope this helps!
>
> Spencer
>
> On Fri, Jan 27, 2012 at 2:51 AM, Phil Spicer <PSpicer at bournemouth.ac.uk
> >wrote:
>
> > Hi,
> >
> > Thanks for all the suggestions... got it working!
> >
> > Kind regards,
> >
> > Phil.
> >
> >
> >
> >
> >
> > On 27 Jan 2012, at 10:29, Adrian Lee wrote:
> >
> > > If that doesn't work you can scatter a couple particles along the
> normal
> > or
> > > velocity of the line. not perfect but it would fill in the gap
> > >
> > > 2012/1/27 Selçuk Ergen <ergensel at gmail.com>
> > >
> > >> Hi Phil,
> > >>
> > >> Increasing the Oversampling rate on the popnet should fix the issue
> > >> actually. If not, I would double check if the animation is
> interpolated
> > for
> > >> subframes.. A timeblend SOP with a start parameter of $RFSTART and an
> > end
> > >> parameter of $RFEND should do the trick I guess.
> > >>
> > >> cheers,
> > >> Selcuk
> > >>
> > >> On Fri, Jan 27, 2012 at 8:59 AM, Phil Spicer <
> PSpicer at bournemouth.ac.uk
> > >>> wrote:
> > >>
> > >>> Hi,
> > >>>
> > >>> Is it possible to birth particles using a Source POP during
> > sub-frames? I
> > >>> have an animated line birthing particles, and it generates strobed
> > lines
> > >> of
> > >>> particles rather than a continuous streak.
> > >>>
> > >>> Any thoughts welcome...
> > >>>
> > >>> Kind regards,
> > >>>
> > >>> Phil.
> > >>>
> > >>>
> > >>> This email is intended only for the person to whom it is addressed
> and
> > >> may
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> > >> error,
> > >>> please notify the sender and delete this email, which must not be
> > copied,
> > >>> distributed or disclosed to any other person.
> > >>> Any views or opinions presented are solely those of the author and do
> > not
> > >>> necessarily represent those of Bournemouth University or its
> subsidiary
> > >>> companies. Nor can any contract be formed on behalf of the University
> > or
> > >>> its subsidiary companies via email.
> > >>>
> > >>>
> > >>>
> > >>> _______________________________________________
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> > >>>
> > >>
> > >>
> > >>
> > >> --
> > >> Selçuk ERGEN
> > >> www.selcukergen.net
> > >> _______________________________________________
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> > >>
> > >
> > >
> > >
> > > --
> > > Adrian Ed Lee
> > >
> > > +44(0)7929517583
> > > Dryrainstudios.com
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> > >
> >
> >
> >
> >
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> > contain confidential information. If you have received this email in
> error,
> > please notify the sender and delete this email, which must not be copied,
> > distributed or disclosed to any other person.
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> > necessarily represent those of Bournemouth University or its subsidiary
> > companies. Nor can any contract be formed on behalf of the University or
> > its subsidiary companies via email.
> >
> >
> >
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=======================================
Andrew D Lyons | Digital Artist | http://www.tstex.com
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