Re: [Algorithms] Kinematic Collision

[pontus b. <her...@ho...>]

Hi, thanks for your reply!

> Date: Sat, 12 Sep 2009 20:56:56 -0700
> From: jw...@gm...
> To: gda...@li...
> Subject: Re: [Algorithms] Kinematic Collision
> 
> 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).
Not sure exactly how this would benefit a fighting move though. Where would the initial movement come from if not from the animation?


> 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.
If I understand you correctly this is exactly what I did my candidate thesis on, converting animation data into forces which are then applied to a ragdoll which correspond to the rig. I never managed to get it looking as well as I'd like though I only tried with explicit integration medthods, and an implicit method would probably lend itself much better to this.


> 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.
Maybe I should look into endorphin, kind of pricy though if I remember correctly.


Pontus


> 
> 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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> 
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