Alice and Wonderland Status

Jeff Pierce jpierce at cs.cmu.edu
Mon Dec 13 20:39:21 UTC 1999


At 09:54 AM 12/12/99, Jan Theodore Galkowski wrote:
> [Tradeoffs between fast/simple/wrong and slow/complex/correct]

>Doesn't this depend on the number of alternative
>representations for the "world" one is willing to
>support?  And upon the formulation of physics one
>wants?

Sure, but the more alternatives you support then the slower / more complex
your system gets, which brings us back to the tradeoff above.

>For instance, a basic result from polyhedral world
>modeling is that there is a transformation one
>can apply to a representation of a world with but
>one mover such that the moving object can be
>reduced to a point and all fixed, polyhedral objects
>are systematically expanded so if the point is ever
>contained by them, one can infer that the polyhedral
>mover in the original world would collide with them.
>The matter gets more complicated once rotations of
>the objects are considered -- requiring one to
>go into higher dimensions to model it -- but it
>remains doable.

Andreas and I never meant to imply that putting physics in is an impossible
task.  The point is just that I don't have time to simultaneously work on
my thesis and implement a complex physical system for Squeak Alice.

>[...]

>At a much simpler level, one thing which is
>essentially in any model of a world is
>representing rotational states of objects.
>I could, for instance, work towards a
>comprehensive representation of polyhedrals
>with positional and rotational states,
>possibly velocities and angular velocities.
>This would serve as a concrete substrate to
>test out my ideas on literate programming.
>
>Or is that too basic and handled well by
>what's out there already?

Representing positional and rotational states is standard.  Representing
velocities and angular velocities (at least explicitly) is less common,
although not unknown.

Jeff





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