Hi,

Wondering if anyone has any ideas on how to solve an issue I'm experiencing with fractal clumping. I'm creating an effect of a piece of fabric building itself. I'm using an animated noise and a ramp that sweeps across a plane to drive the hair length - essentially growing the fur from a value of 0.

Inside the hairgen node I've added a hair clump. The motion of everything is fine if fractal clumping is set to 0, but if the value is above this, all the clumps change position from frame to frame and I end up with a very chaotic result. Once the gradient ramp has finished and the fur length stops changing, the clumps remain in place.

I'm wondering if changing the length of the fur is causing different hair clump curves to be generated on each frame and maybe this is the issue. Any thoughts are much appreciated!

I see a change log about this issue:

Houdini 16.0.575 Fixed a bug in the Hair Clump SOP that could cause hairs to find different clumps on each frame of an animation.
This was because we didn't use the restroot attribute to do the neighbor lookup.

Mon. April 10, 2017

Have you tried the latest daily build?

Hey thanks for the tip! I haven't but I'll definitely give it a try. Also, I re-worked my setup so that the length attribute happens after the clumping in the hairgen. Initially I was controlling the length within the guides. That fixed things quite a bit but I still get small amounts of random fibers snapping to different clumps. Will test the new build tonight.

I'm getting this in version 17 with Vellum Hair solver. The fiber hairs are jumping with clump SOP. They work fine without the clump. I'm trying to use the “groom fetch” SOP but having limited success getting the rest attribute to come in and be used in the hair fiber creation.

Hi people!
Anyone, has resolved this problem in Houdini 17?

Think I found the issue.
I was getting this exact same issue from the hair clump sop. I did some tests and disabled each parameter one by one. I turned the 'Stray Rate' to 0 and the popping stopped.

Is this a bug?

H17.5.173

Hi,

Posting in a dead thread as i have also stumbled on this issue, could not find anything related to this.

Basically if there are guides or curves which are getting animated and then when u try to add hair clumps to these with the curl or the frizz from the guide process node, the clumps keep changing the position each frame. Is this how its supposed to be? Since i guess the points P attrib changes each frame and which is why the noise keeps changing?

Any suggestion related to this?

I am having a similar issue in houdini 18.0.566

When animating a mesh, there is swimming noise moving through my hair. I was able to get it down to the hairclump in the hairgen add curl attribute.

Is there a way to pass a rest attribute to the corehairclump node?

When I add curls in the hairgen with the hairclump, i get swimming curls when it animates. What is the proper workflow for curls? I have seen some very cool examples of this in some demos for houdini 16. Is the curl attribute only for guides? would be nice to be able to add it at the hairgen level.

Thanks in advance,

Rob

robau2bitfx
I am having a similar issue in houdini 18.0.566

When animating a mesh, there is swimming noise moving through my hair. I was able to get it down to the hairclump in the hairgen add curl attribute.

Is there a way to pass a rest attribute to the corehairclump node?

When I add curls in the hairgen with the hairclump, i get swimming curls when it animates. What is the proper workflow for curls? I have seen some very cool examples of this in some demos for houdini 16. Is the curl attribute only for guides? would be nice to be able to add it at the hairgen level.

Thanks in advance,

Rob

Hello Rob ,

I am facing same issue in H 18.0.597 in the curling option in the clumping node ,
Did you manage to find any solution for this ?

Thanks .

Time to revive this thread! So, I've just encountered a similar issue. From one frame to the next, groups of hairs (I don't know if they are technically clumps or not) are either snapping to a new position or simply disappearing (it's not always clear just which of those options is what's going on). This happens even when there is no simulation at work - so just on the deformed guides. I'm about to start detailed testing but that could take a very long time and I'm hoping someone here can give me some helpful information that isn't already in this thread. Anyone?

does your rest/animated skin have consistent topology among all frames?

tamte
does your rest/animated skin have consistent topology among all frames?

Yes, it does.

fbb

tamte
does your rest/animated skin have consistent topology among all frames?

Yes, it does.

Were you able to figure this out? I've been struggling with the exact same issue on just deforming guides. no sim.

Seems like I'm running into the same issue, as soon as I add fractal clumping to the hair it starts jittering when the guides are animated or simulated.

Anyone figured out a solution ?

Houdini 19.5.534

I found solution that allows to workaround this issue a bit. It only work's with deforming guides not with simulated. In the hair generate node just go for guide deform node at the end of your setup, it seems to keep fractal clumping together.

Same problem here with hairs jumping between clumps on animated guides...