baking hair dynamics

I’ve created a gorilla with hair/fur (via particles) and applied “hair dynamics”, then animated it.

The first time I bake the “hair dynamics”, it works great.

However, as I adjust the animation and “free bake” and then “bake” again so that the dynamics can recalibrate to adjustments in the animation, it appears the “hair dynamics” start degrading – i.e., the hair/fur starts to die into the mesh (emitter) and bald spots begin to appear where there was once hair/fur.

To be more specific, it’s not like when the fur goes completely all over the place like the effect one gets when the “bake end frame” count is less than the “animation end frame” count.
It’s much more subtle and looks like the emitter mesh is just out of sync with the “hair dynamics”.

I’m looking for a way to “cleanly” eliminate the old bake so that I can “re-bake” it clean or a way to resolve the “hair dynamics” degradation issue as one makes adjustments to the animation.

Any help would be great. Thanks in advance.

Have you tried deleting the blendcache folder before a new bake? This will insure that completely new Hair Dynamics data is being written to the physics cache. However, if you have other physics going on it will also delete that, so be cautious, it’s a last-ditch move.

Lately I’ve also noticed that Hair Dynamics doesn’t seem to act all that reliably, but haven’t had a chance to document it. If you can demonstrate the “degradation” reliably it might be worth a bug report. AFAIK given the same conditions from one bake to another, the hair should react identically. Small changes in emitter animation will alter the reaction of the hair somewhat, but it should be generally consistent.

Thanks. It’s easy to replicate. Is there a typical channel through which to report this type of bug?

The 2.6x bug tracker is at

http://projects.blender.org/tracker/?atid=498&group_id=9&func=browse

You’ll need to register, etc. Good info there about what & how to report.

Just want to confirm that I’m getting the same problem using a hair system in 2.61. The first bake looks OK, but needs some tweaks in places. After using Free Bake, the second bake often results in the hair exploding all over the place, even though only a single parameter was changed by a small amount. I’ve seen this now in at least three different hair systems.

EDIT: After trying unsuccessfully to get a clean bake from my hair system, it has now become so bad that it is totally unusable. Even deleting the cached data does not “clean the slate” for a new bake, the hair just goes batshit. WTF is going on here? This was never the case in pre-2.5 versions.

EDIT^2: Found a workaround – do not use Disk Cache. By baking the physics into memory, I’ve been able to get the proper response to small changes in hair parameters. Joy. Makes for a bigger 'blend, though.