Hi there,

I'm working on a custom groom in Houdini, and I'm running into problems using partition curves with the Hair Clump SOP. I have the partition curves working great (via Guide Partition) with the Hair Generate SOP, but no matter what I try, Hair Clump just ignores them and clumps hairs across the partition, making a mess inside the groom.

Normally I would dig into the SOP's code and figure out what's going on, but Hair Clump is backed by Hair Clump Core, which I don't have a way to look inside. Has anyone had success in getting clumping to work with partitions, and if so, what's the secret magic?

I've attached a few images, that show the guides, the partition guides, the generated hair, and the results of the Hair Clump SOP. As you'll see in the last image, some of the clumped hairs are in the middle of where the head would be, because (I think) the hair clumps were averaged between guides from either side of the partition lines, as if the partition curves weren't being used.

I finally figured it out! There were quite a few things that had to be just perfect for it to work:

- I had to create some custom clump curves to drive the clumping; run these curves through a Guide Partition SOP to merge them with the partition curves; add a `rest` attribute to the combined set of clump and partition curves with a Rest Position SOP; and then pipe the output of that into the Hair Clump SOP's "Custom Clump Curves" fourth input
- I had to add a `rest` attribute (with a Rest Position SOP) to the skin geometry that went into the Hair Clump SOP
- I had to set the Hair Clump SOP's "General > Crossover Rate" parameter to 0 (this seems to drive the amount that clump can cross over partitions, which unfortunately the Hair Clump SOP documentation [www.sidefx.com] fails to mention)

With all of that in place, I finally get the partition-driven clumping I would expect.

Hip file please??

Hey thanks for this!! I think I figure it out as well, but would you main to post an image of the graph or a quick example? Would be really usefull since there arent good tutorials or demosntration out there :/