Re: Kinematic Collision

> Game development isn't about solving the general case;
> it's
> about ensuring the special (failure) cases don't
> happen.  It
> is about the smoke and mirrors, the bang for buck.

It's not really that general a case, all you need is to include a built-in level editor or and/or significant dynamic geometry and any sort of author-time restriction-based approach (such as the proposed "input geometry must be nice for character controllers to work") becomes unacceptable.

To segue back to talking about physics-based character controllers: we're using a rigid body with kinematic constraints driving orientation, and we're driving the movement through the world via constraints (motorized velocity constraints between the player's center-of-mass and nearby points on the environment). This works great so far, but it's also a very sim-centric type of movement -- like Gish rather than Mario.

One of the bigger unsolved problems for our controller is: how do you determine a consistent "down"/ground direction?

In most games this is simplified by following the convention that only upward-facing surfaces can be walked on; if instead you want to allow smooth movement along any surface (walls, ceilings, ragdolls) this gets a lot harder because you can't use (0,1) as the a priori "down" direction -- all directions have to be considered equally valid. 

If there are only one or two closest/contact points this is relatively easy, but when e.g the player is surrounded by a pile of small objects.. things get messy.

Raigan



--- On Wed, 9/9/09, [email protected] <[email protected]> wrote:

> From: [email protected] <[email protected]>
> Subject: Re: [Algorithms] Kinematic Collision
> To: "Game Development Algorithms" <[email protected]>
> Received: Wednesday, September 9, 2009, 3:02 PM
> 
> Raigan wrote:
> > In a more dynamic world, where there are lots of
> physics-based
> > objects and/or destructible shapes, it's not so
> trivial (maybe
> > impossible) to guarantee that the scene is nicely
> behaved with no
> > tiny channels or other problematic geometry.
> Especially if you're
> > trying to allow characters to move on/across such
> dynamic shapes,
> > rather than simply treating them as untraversable
> obstacles.
> 
> Game development isn't about solving the general case;
> it's
> about ensuring the special (failure) cases don't
> happen.  It
> is about the smoke and mirrors, the bang for buck.
> 
> 
> Christer Ericson, Director of Tools and Technology
> Sony Computer Entertainment, Santa Monica
> 
> 
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