Stable point ids at ends of Lsystem tree

[jim c]

I've got a tree that's generated via the L System SOP. I'm extracting the end points of the branches to grow leaves on them, after running the points through a SOP Solver to add some custom pt attribute data used in growing and animating the leaves.  I notice that the point ids kind of jump all over the place as the lsystem grows over time. Is there a way to get a stable set of points such that the oldest point is point 0, and the next is point 1, and so on? Is it just a matter of sorting the points by age?

[sebkaine]

have you check point attribute in your lsystem it give you all you need by default ?

cheers 

E

lage.hiplc

[jim c]

Thanks, but here's what I'm talking about - I want to track one specific point as the lsystem grows. See these screenshots from your file:

 

So that's frame 1 above, and that's the point I want to track - I've resorted by lage  

 

Now as the frames changes (frame 14 above), the point switches as well, now the point I wanted to track (circled in red) gets missed and instead I'm left with a different point. And then a few frames later it switches again:

 

This is what I'd like to prevent. I think what I'm after is something like how a particle system treats id, so that they are stable as the system grows?

 

[sebkaine]

i see your point jim

in fact it is easy to isolate the extremity point (cf hip)

but if you want to isolate 1 specific extremity point that is far more tricky ...

The things is that you miss a crucial attribute, the id of the previous gen point that create the current extremity.

 

If it was me i would base my growth setup either on

- POP recursive stuff + pcopen stuff to control proximity 

OR

- growth stuff throw seed propagation into sop solver

 

However to solve this in L-system

- i would start from the last frame and isolate it as ref frame 

- invert the anim 

and try to look at the closest point at each frame. but i haven't suceed yet ... cause point disapear and track this is not obvious !

 

lsystem_002.hiplc

Edited September 25, 2016 by sebkaine

[jim c]

Thanks. I sort of found a work around (I was able to use a bounding sphere to select a small group of points and then since the point I wanted was closest to the ground, just sorted by Y). But ultimately it would be nicer to have a general solution.