[Sidefx-houdini-list] Time warping a point cloud

Pablo Giménez pablogipi at gmail.com
Thu Aug 7 06:12:05 EDT 2008


Time Blend works much better and faster if it can get the data from a Cache
SOP, at least all the times I have used it is much better to put a Cache
before it than to use only the Time Blend.
Evan sometimes the only way to get correct results from the Time Blend is
putting the Cache before it.

2008/8/7 Guillaume Laforge <guillaume at alamaison.fr>

>
> >... you can use the Time Blend SOP after  a Cache SOP and the you can use
> Time Warp SOP or Time Shift SOP to
> retime the animation, it works pretty well.
>
>
> I don't understand why you need a Cache Sop before the Time Blend ?
>
> If I understand well,  the difference with the Time Blend and the Cache
> is that the Time Blend interpolate also the velocity attribute ?
>
>
> Guillaume
>
>
> Pablo Giménez a écrit :
> > You can do a time wrap, I use to prefer the time shift, but using a ramp,
> > and indexing into the ramp.
> > I have used it recently to retime several animation in base of some stamp
> > parameter so I can get several copies of teh same animated thing but
> > retimed, and works really well.
> > For me it gives more control than using only the cache and because you
> are
> > using the time blend you ensure that you get correct results for moiton
> blur
> > in case you need it.
> > Hope this helps.
> >
> > 2008/8/7 Guillaume Laforge <guillaume at alamaison.fr>
> >
> >
> >> Hi Pablo,
> >>
> >> Yes I've got the same number of points but I need to control the time
> >> warp with an fcurve so "chf" expression to drive the index of a cache
> >> SOP works better in my case, unless I miss something with the Time Warp
> >> SOP ?
> >>
> >> Cheers
> >>
> >> Guillaume
> >>
> >> Pablo Giménez a écrit :
> >>
> >>> Hey Guillaume, I don't know if the topology of your point cloud is
> >>>
> >> changing,
> >>
> >>> probably yes, but if this is not the case you can use the Time Blend
> SOP
> >>> after  a Cache SOP and the you can use Time Warp SOP or Time Shift SOP
> to
> >>> retime the animation, it works pretty well.
> >>>
> >>> 2008/8/6 Guillaume Laforge <guillaume at alamaison.fr>
> >>>
> >>>
> >>>
> >>>> Lot of very good advices. I've got much more control on my little
> points
> >>>> now :).
> >>>>
> >>>> Thanks Ben.
> >>>>
> >>>> Cheers
> >>>>
> >>>> Guillaume
> >>>>
> >>>>
> >>>> Ben Schrijvers a écrit :
> >>>>
> >>>>
> >>>>> And for the time warping... uhm... maybe use an animation curve
> instead
> >>>>> of $T  :-)
> >>>>>
> >>>>> Ben Schrijvers wrote:
> >>>>>
> >>>>>
> >>>>>
> >>>>>> Hi there,
> >>>>>>
> >>>>>>  I just gave that a go and you just need to set the geometry CHOP's
> >>>>>> start and end paramers to $T.
> >>>>>> In that way it just reads the current frame.
> >>>>>>
> >>>>>> With time slicing and things like lag, jiggle etc you can only play
> >>>>>> forward so I geuss you bring back the channels into sops and render
> >>>>>>
> >> out
> >>
> >>>>>> a point cloud sequence again.
> >>>>>>
> >>>>>> cheers,
> >>>>>> benS
> >>>>>>
> >>>>>>
> >>>>>> Guillaume Laforge wrote:
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>> Hellooooww Ben :),
> >>>>>>>
> >>>>>>> The timeslicing option sounds interesting but I can't find a way to
> >>>>>>>
> >>>>>>>
> >>>> activate this parameter directly in the geometry CHOP.
> >>>>
> >>>>
> >>>>>>> It is possible to turn it on in the lag CHOP but the memory could
> be
> >>>>>>>
> >>>>>>>
> >>>> full before this node :-/.
> >>>>
> >>>>
> >>>>>>> I'm at home know, so I can't test on my point cloud sequence. I
> will
> >>>>>>>
> >>>>>>>
> >>>> let you know how it works tomorrow.
> >>>>
> >>>>
> >>>>>>> Thanks.
> >>>>>>>
> >>>>>>> Guillaume
> >>>>>>>
> >>>>>>>
> >>>>>>> On Tue, 05 Aug 2008 20:01:16 +0200, Ben Schrijvers <
> >>>>>>>
> >>>>>>>
> >>>> ben.schrijvers at guerrilla-games.com> wrote:
> >>>>
> >>>>
> >>>>>>>
> >>>>>>>> Bonjourrr...
> >>>>>>>>
> >>>>>>>> For the time warping part you indeed are better of with a sop
> >>>>>>>>
> >> method.
> >>
> >>>>>>>> For CHOP's tou might consider looking at timeslicing. Each CHOp
> has
> >>>>>>>>
> >> a
> >>
> >>>>>>>> toggle in the last tab.
> >>>>>>>> Not sure if it's documented somewhere but I believe it means it's
> >>>>>>>>
> >> just
> >>
> >>>>>>>> keeping a few frames in memory.
> >>>>>>>> Not all CHOP's will work but things like lag, jiggle or spring
> will.
> >>>>>>>>
> >>>>>>>> cheers,
> >>>>>>>> benS
> >>>>>>>>
> >>>>>>>> Guillaume Laforge wrote:
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>> Hi,
> >>>>>>>>>
> >>>>>>>>> I'm trying to do some time warping on a bgeo sequence  of points
> >>>>>>>>>
> >>>>>>>>>
> >>>> coming
> >>>>
> >>>>
> >>>>>>>>> from a fluid simulation. I thought that I could use CHOPs to
> >>>>>>>>>
> >> control
> >>
> >>>> the
> >>>>
> >>>>
> >>>>>>>>> motion but
> >>>>>>>>> unfortunately when I reference my bgeo file in a geometry CHOP,
> it
> >>>>>>>>>
> >>>>>>>>>
> >>>> gives
> >>>>
> >>>>
> >>>>>>>>> an error or crash Houdini. I've got 7000 points in my bgeo files
> >>>>>>>>>
> >> and
> >>
> >>>> a
> >>>>
> >>>>
> >>>>>>>>> duration of 120 frames. Maybe it is to much data to handle in
> CHOP
> >>>>>>>>>
> >> ?
> >>
> >>>>>>>>> I tried the Timewarp SOP too but it gives less control than CHOPs
> >>>>>>>>>
> >> (no
> >>
> >>>>>>>>> lag, jiggle etc...).
> >>>>>>>>>
> >>>>>>>>> Any advices to setup a time warping on a bgeo sequence of 7000
> >>>>>>>>>
> >> points
> >>
> >>>> on
> >>>>
> >>>>
> >>>>>>>>> 120 frames is welcome !
> >>>>>>>>>
> >>>>>>>>> Thanks
> >>>>>>>>>
> >>>>>>>>> Guillaume Laforge | la maison
> >>>>>>>>> _______________________________________________
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> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
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> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>> --
> >>>>>>> Guillaume Laforge | la maison
> >>>>>>>
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-- 
Un saludo
Best Regards
Pablo Giménez



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