Points Attribute transfer Dilemma - @ptnum

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Joined: 2月 2015
Hello Guys.

I got stuck here in a middle of an project and i can't find a solution.

My problem is : I have a grid of points , and an animated point running over the surface of the grid. My “running” point have an attribute that is transferred ( via attrib transfer SOP inside an Solver) to the grid points by an proximity radius.

then I use the transferred attribute to isolate only the grid points that are touched by the “running”point. But the @ptnum of the remaining points is changing. And i need the @ptnum to grow in the order detection ( @ptnum 1, 2, 3, 4, 5 etc)

why is that happening?

to understand better I've attached the scene file

ptnum_chaos.hip (110.9 KB)

Bogdan Lazar
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Joined: 6月 2014
Hi Bogdan,

The hitch there is that you're removing all the points on the same, single timestep -with the delete SOP not having any knowledge of what order the points were “tracked”. In order to get it going, we need some way of recording the order they were added in, the Solver SOP being the natural place to put this.

Here's a couple of examples, the first creates geometry inside the solver, and so we get well-ordered points for free. The second option uses attributes much like before, but I've added a second attribute that gets set to the frame number when the point gets set to active. Then later on you can sort your points based on that ‘active_frame’ attribute.

Hope that helps,


ptnum_chaos_001.hip (131.5 KB)

Henry Dean
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