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

Nicholas Pliatsikas nick_p102 at hotmail.com
Thu Aug 7 07:57:59 EDT 2008


Yup we figured that much :D but then you also have the problems with particle birth, you cant retime particles that haven't been born yet so offsetting or speeding up particles is a problem too. :¬D It also means when you slow things down you end up with redundant points as you have more points available then your are positioning.So you have to have a reserve of particles to begin with, not just by keeping them alive. Post delete these based on pstate and so own. Theres a few work arounds but its all pretty messy.

> Date: Thu, 7 Aug 2008 12:43:02 +0100> From: Sean.Lewkiw at CIS-London.com> To: sidefx-houdini-list at sidefx.com> Subject: Re: [Sidefx-houdini-list] Time warping a point cloud> > You might find you have to sort your channels by ID... this is an option > in CHOPs. > > Also, you might have to have in reserve a bunch of particles that are > added to your sim so that the point count never changes, (that is, find > out the maximum number of points that ever exist, and make sure that > this is constant throughout the shot through copy SOP trickery). That > means that points can't die though. Basically, your non-existent > particles are left at 0,0,0 and scaled to zero until the channel they > match in CHOPs exists, then they will suddenly pop into place. > > Yup, this is a real hassle!> > Sean> > Nicholas Pliatsikas wrote:> > 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.> > > > > -- > Sean Lewkiw> --> CIS London> 130 Shaftesbury Avenue> London W1D 5EU> --> +44 (0) 207.031.1138 (P) (Direct)> +44 (0) 207.031.1136 (F)> +44 (0) 795.606.7245 (M)> --> Composite Image Systems London Ltd> Registered Office: Denham Media Park, North Orbital Road, Denham, Uxbridge, Middlesex UB9 5HQ> Company Registration No. 5577229 England> > > _______________________________________________> 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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