Re: [Xvrml-agents] on animation

[Jeff S. <je...@ar...>]

On Jun 27, 2005, at 8:18 PM, Miriam English wrote:

> We need to simplify animation.

I agree

> Currently, in vrml and xvrml there are some fairly arcane animation  
> capabilities (all the interpolator nodes)

this is indeed the next thing in the Project work-plan:
revise the interpolators


> they require foreknowledge of the start-point, end-point, start- 
> time, and end-time of any movement. [...]

the same basic problem Dave and others have pointed to

> The only sensible way achieve simple, flexible animations is the  
> use a different, simpler kind of
> movement: a move command consisting of a force operating upon an  
> object's mass.

so the idea is to simplify the animation declaration in the xVRML code
and leave more of the how-to-act to the implementation
[and thus to be spelled out in spec text]
??

> Luckily the pre-existing Open Dynamics Engine (ODE) lets us avoid  
> most of the work here.
> (See http://sourceforge.net/projects/opende/ and http://ode.org/ )  
> We just need a couple of
> extensions to the (xvrml) language to take the new, simpler move  
> command: a mass attribute
> for objects, and a force.

so any given geometry node may have an optional mass attribute set
and will have a default mass value??


> With a simplified method of animating objects, moving avatars in  
> interesting
> and progressively more complex ways becomes much, much easier to do.
> Now, to specify movement of a hand to an object [...]
> All you need is to apply a force to the hand. ODE moves it, taking  
> into account
> its mass and the IK links to lower- and upper-arm.

ahhhhhh
there is the "kicker"...
how to deal with inverse-kinesmatics links
and their complexity

I'll have to take a look at how ODE deals with this
for I haven't a clue

it seems to me the danger of increased complexity
is raised by adding responsibility for specifying IK

is this a false perception?

> - One effect is that the walk animation applied to a dwarf will  
> play differently when used on a giant.
> The user doesn't need to alter timings and many intricate aspects  
> of the animation; it will just run
> differently because it is affected by mass.

this is indeed part of what I am after

> This has wider implications for end-use too. Rodney Brooks showed  
> how to program robots
> using a kind of distributed intelligence, where each leg has its  
> own "ganglion" coordinating
> only loosely with the others. This produces very flexible and  
> adaptive behavior. Using a
> simplified force/mass model for animation in makes it possible to  
> create simple, open-ended,
> cascading animations that are similarly flexible and adaptive.

and this is also very desirable

thanks miriam
this is worth our discussion...
but now I have more stuff to read (at ode.org)

comments from others?
jeffs