Re: [Algorithms] Kinematic Collision

[Jon W. <jw...@gm...>]

First: Fighting games are somewhat special. I wouldn't expect you can
use a "standard" character controller for that.

However, in general, you'll want the animation to be driven by the
movement, and not the other way around. Each frame, you determine how
far you've traveled since the last frame, and forward the animation an
appropriate amount to avoid foot sliding. (The animation is marked up,
or you measure this based on certain named bones).

Now, you have another problem with fighters: that of an irresistible
force hitting an immovable object. You *can* play back animations as
force constraints on a rigged character/ragdoll. It doesn't have to
look sloppy, if you use enough force in the joints, and also a little
bit of look-ahead to get the velocity as well as the position right.
Don't know if it's good enough for a fighter, though.

The problem then is when the character runs into roadblocks that
simply aren't in the animation. You might want to apply a limited
amount of force (enough to get going with super-human speed, of
course), and if the limbs are too far out of place after a while,
cancel the animation/attack -- you probably tried to punch a mountain
wall or something similar. And once you start to integrate animation
and physics even more, you might start expressing animations as
"desires" -- "I want to land my left fist on his nose in 400
milliseconds, and I think it will be *there* at that time." Similar to
 Natural Motion / Endorphin in real-time, with player guidance,
perhaps.

If you or anyone else learn anything more about this, I would be very
interested in hearing about it!
Sincerely,

jw



On Sat, Sep 12, 2009 at 2:13 AM, pontus birgersson
<her...@ho...> wrote:
> This thread is really interesting (or was up to a point). Before it dies
> down I'd like to ask for some recommended reading. This is something that I
> find a true pain whenever I start a new project because there's animation
> and there's physics and they both want different things and are VERY rigid
> in how you can use them.
>
> In my experience which mostly dealt with fighting games, the attack
> animations will include a player translation which needs to be exact in
> order for it to look good, i.e. I must use translation on individual frames
> and NOT apply a force which delays and smudges movement.
>
> The animation being translated first poses the problem of not letting the
> player’s world position go out of sync with its pelvis (root joint) so
> various spatially based algorithms don't get thrown off. This can of course
> be solved by tricking around with spatial delta for each animation key frame
> and applying the correct translation/rotation on a per frame basis. After
> this step I end up taking the transformation from the pelvis bone on that
> particular key frame and instead apply it directly to the entity world
> position.
>
> When I've done this it feels like I've effectively contradicted the way I'm
> allowed to work with physics simulated objects though. Unless the physics
> integration method is an implicit one, as far as I understand it, I'm not
> supposed to move the object using translation, only by force or suffer the
> hell that is unstable physics...
>
> So if that's the case, and do point out if I'm wrong, what does this
> character controller that I keep hearing about do differently from this that
> make physics and animation, not only speak the same language but also like
> each other?
>
> Regards
> Pontus Birgersson
>
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