[Bf-committers] Durian/Hair Troubles

[bjornmose]

first glance at the example:
same problems reported at ED Plumiferos ..
time ( on goal , colliders  any thing 'outside' ) is too discontinuous 
reads  as: the 'outside' is too fast to keep physics in sync.
this is a intrinsic problem of the blender animation system .. : no 
canonic way  to ask for the 'inter frame' state of any object.
work around:
1. isolate physical actors ( with layers, groups ... what ever )
2. run isolated system at 1/10 or less time scale
3. join back in proper time scale
4. yada yada
..
ask the the physics wizards, invited to BC
grumpy old BM

bjornmose schrieb:
> Well kept building 2.5 every now and then ..
> May be I can give some hints on physics solvers ?
> Joe may want to ask me .. ( using  ^this^  email  in private )
> other than that .. I'll try to squeeze some time out off my schedule to 
> investigate the given files.
> BM
> P.S. 2.5 is going amazingly well, respect!
>
> Campbell Barton schrieb:
>   
>> Over the past weeks we have been attempting to get hair working for
>> all our shots.
>>
>> So far Joe has been working on changes to the solver code in our own
>> branch but the results solve some problems while causing others (Im
>> not sure on the details).
>> Joe says the problem is the goal code, which is a little hackish, and
>> the bending springs don't work right for hair.
>> so it would be a real help is dev's who are familiar with these
>> problems can investigate.
>>
>> I haven't been involved in the hair solver side of things, mostly just
>> making sure its possible to run the simulations on proxies on our
>> linking setup, testing and setting up bakes for our shots, have cache
>> save/load etc.
>>
>> At the moment it would even be good to see a mediocre hair sim even if
>> their are intersections with the head.
>>   
>>     
>>> >From tweaking the settings I had trouble even getting this, though its
>>>     
>>>       
>> possible that the problem with my settings.
>>
>> Would greatly appreciated if any developers have time to look into this.
>>
>> Notes:
>> - can test in trunk or render branch, give different results but
>> neither are great.
>> - collision is off in this file, seems very tricky to have working
>> stable, (sintel's low poly head mesh is a collier).
>> - try run the bake on 2-3 sec for fast updates (Brecht has done some
>> work on realtime redraw's but not ready to commit)
>>
>> Heres a blend file with Sintel's hair and the animation (1.0mb)
>>  http://durian.blender.org/wp-content/uploads/05.8b.blend
>>
>> Heres a video of what I managed to get so far (2.0mb)...
>>  http://durian.blender.org/wp-content/uploads/05.8b.ogv
>>
>> Here are the settings used in the animation...
>>     psys.cloth.settings.quality = 30
>>     psys.cloth.settings.structural_stiffness= 12.0 # good overall
>> value to control stiffness, 12 is needed for running up stairs
>>     psys.cloth.settings.pin_stiffness = 0.5 # above 0.6 can become unstable!
>>     psys.cloth.settings.bending_stiffness = 80.0
>>     psys.cloth.settings.spring_damping = 30.0
>>     psys.cloth.settings.air_damping = 2.5
>>     psys.cloth.settings.mass = 0.015
>>     psys.cloth.settings.internal_friction = 0.1 # 0.9 makes hair too symmetrical
>>     psys.cloth.settings.structural_stiffness= 60.0
>>
>>   
>>     
>
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