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

Nicholas Pliatsikas nick_p102 at hotmail.com
Thu Aug 7 07:00:53 EDT 2008


Im guessing the cache is just to stop any unneeded computations or always dragging files off the network and to stop any wierdness on sims. It seems to be very difficult to retime particles sims with changing point numbers at birth and death, Especially through chops. We are currently trying to figure out the best approach for this but looks like lots of over sampling and reading back just the data we need at specific times, is one of the stable methods of doing this.
 
To be honest the way I would like to see this implemented in houdini with a time control on the top nodes of dopnets and popnets to define the current simulation time which be default would be $FF of course but could be replaced by keyframes etc. Maybe time for an RFE considering how often we need to do this sort of work.Nicholas Pliatsikas



> Date: Thu, 7 Aug 2008 11:29:35 +0200> From: guillaume at alamaison.fr> To: sidefx-houdini-list at sidefx.com> Subject: Re: [Sidefx-houdini-list] Time warping a point cloud> > > >... 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> >>>>>>>>> _______________________________________________> >>>>>>>>> Sidefx-houdini-list mailing list> >>>>>>>>> Sidefx-houdini-list at sidefx.com> >>>>>>>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>> > >>>>>>>> _______________________________________________> >>>>>>>> Sidefx-houdini-list mailing list> >>>>>>>> Sidefx-houdini-list at sidefx.com> >>>>>>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>> > >>>>>>> --> >>>>>>> Guillaume Laforge | la maison> >>>>>>>> >>>>>>> _______________________________________________> >>>>>>> Sidefx-houdini-list mailing list> >>>>>>> Sidefx-houdini-list at sidefx.com> >>>>>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>> > >>>>>> _______________________________________________> >>>>>> Sidefx-houdini-list mailing list> >>>>>> Sidefx-houdini-list at sidefx.com> >>>>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>> > >>>>> _______________________________________________> >>>>> Sidefx-houdini-list mailing list> >>>>> Sidefx-houdini-list at sidefx.com> >>>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list> >>>>>> >>>>>> >>>>> > >>>> _______________________________________________> >>>> Sidefx-houdini-list mailing list> >>>> Sidefx-houdini-list at sidefx.com> >>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list> >>>>> >>>>> >>>> > >>>> >>>> >>> > >> _______________________________________________> >> Sidefx-houdini-list mailing list> >> Sidefx-houdini-list at sidefx.com> >> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list> >>> >> > >> >> >> > > _______________________________________________> Sidefx-houdini-list mailing list> Sidefx-houdini-list at sidefx.com> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
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