[Sidefx-houdini-list] Behavioral type animation

Jeff Wagner jeff at sidefx.com
Thu Jan 12 09:55:58 EST 2006


Here's a partial point list of ideas/techniques you could employ in your 
behavioural flocking system:

- CHOPs is the engine to manage all pre-animated sequences. Drives 
either rigged characters or geometry sequences.
- Copy Stamping techniques to control geometry sprite sequences.  Can be 
slow but is quite user-friendly to implement.
- Point instancing can play a role for background characters that 
represent ambient movement.
- Particles with properly managed local coordnate systems separated but 
influenced by the particle's velocity
- "Vision" of each particle for obstacle avoidance implemented in POPs 
by firing rays -> VEX context in POPs (VOPs). Can detect actual surafces 
or objects littered with point clouds. A few options here needed to be 
tested.

Big Questions:
- How many critters do you want to interact? How many represent ambient 
background movement? How many "hero" critters?
- Do you work with geometry sprites, rigged characters (Capture/Deform 
SOPs), or a combination of both?
- How many transitions per character?
- Separate Head (bearing or look-at interest) from hips-upper body from 
legs (walk cycles). How do you do this? How do you ensure that 
characters have properly separated regions to override each bit from the 
others? Do you need to go this far?
- Obstacle avoidance can be slow so how you implement this can be 
involved.  How intricate are the reactions?

One can use Massive as inspiration.  It has a proven method to doing 
very large crowd sims although it takes a fair bit of work to get going 
in itself.  To recreate bits of this in Houdini isn't trivial but it is 
well worth the effort.  You can't expect to get the efficiency levels of 
massive but then again, you can work things in blocks of crowds and use 
smarts to grunt some things through.  Depends on how many critters you 
need to sim.


-jeff

rafal wrote:

>    First: I came from Maya background. So I thought I can do this in 
> Maya but.... it can takes large amount of time becouse I should learn 
> MEL on more advanced level. Second: I saw one ILM guy dvd about 
> instancing(Maya also) who explain how made it using particles 
> expression. Generally speaking, he has cycles of a characters 
> animations: run, crawl, etc, and also transitions, so transition from 
> example run to crawl. I'm not programnmer so I still try to analize 
> his mel code, but again it takes time.
>
>    I thought it can be simpler in Houdini coz everyone says it allows 
> one to do advanced stuff with little programming/scripting(maybe I'm 
> wrong). Talking about collisions I get an idea to fake it. So when U 
> got two points on surface: A --> human , B --> collisionObject , it 
> should be enough to compute distance between these two and when 
> distance is lower than certain value proper cycles should be played.
>
>    I can't answer, yet, for rest questions :/
>
>
> r|m
>
>
> Peter Robbinson wrote:
>
>> How are you going to determine which behaviours are triggered? What 
>> is your trigger, proximity? collision?. Which one of your characters 
>> is going to determine the behaviour triggered?
>>
>> PeterR
>>
>> rafal wrote:
>>
>>> Hi people!
>>>
>>> Let say I have humans instanced on particles. Humans walk on plane 
>>> and when one of them is very close to some geo he change their 
>>> behaviour.
>>>
>>> What's the proper solution to achieve this kind of effect? Should I 
>>> have diffrent animation cycles or motionClips or something else?
>>>
>>>
>>> r|m
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-- 
Jeff Wagner, jeff at sidefx.com, Senior Technology Consultant
Side Effects Software, www.sidefx.com, Toronto, Ontario, M5V 3E7
tel: (416) 504-9876, fax: (416) 504-6648





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