Something I've done in Maya by emitting particles at the center point of a list of objects then using that particle to drive their transforms with per-particle expressions, any tips on how this is done in Houdini would be great. Thanks!

What your talking about is a very old school Houdini technique.
In loose terms depending on your situation, you want to look at creating a foreach SOP to loop through each piece of geometry and add a point at the centroid. then feed those generated points as the source for your pop souce and jist create on the first frame of course counting how many source points you have , then after the sim > apply those points back onto the geometry pieces via a copy sop.

expressions to look up
npoints()
centroid()

Theres a ton of old threads about it on this forum, see what you can come up with

Rob

very cool, thanks I'll dig into some searches

Hi,
Here is a simple example show the centroid () expression to map points onto pieces. As ever the best approach is to ruff things out and try to solve small problems then bring everything together.
The biggest problem is going to be mapping the points coming from pops to the correct piece of your fracture > My grey matter doesn't remember the exact technique but it had something to do with passing an attribute from sops into pops and using a prim sop ! > then to a copy sop.

Rob

Transform piece sop is your friend.

You can also do this with VOP SOP !

1. Add centered points for each pieces
2. Move All pieces to home (center of the grid)
3. Add unique ID for each piece and it's centered point
4. Convert your points to Particles and move them
5. Take position of each point and transform it's piece with this position (with VOP SOP and checking Unique ID ! )

And this is a simple project about this :wink:

Exactly what I was looking for, thanks for the example set up

In this scenario, how would I take something like age to control SOP scale? In the past I've used VOPSOPs to map age to Cd which works great with copy stamping to control geometry scale for instance, but I'm at a loss at the moment on how this would be done purely with VOPSOP