Re: coordinate systems

James Waldrop ([email protected])
Wed, 24 May 1995 10:01:15 PDT


Glen Wheless wrote:
>
>as an oceanographer and numerical modeler, i'd vote for the
>z is up convention. our standard convention is z is negative
>below sea level, positive above. atmospheric folks think this
>way as well, i believe.
>

As many people have pointed out, any VRML node is one simple rotation
away from being oriented along any axis you like. I suggest we
formalize on what's already used, and let God sort out the rest.

>the suggestion of a fourth axis for temporally varying data
>is a good one.

It actually struck me as completely unworkable. It seems that to
achieve realistic, i.e. smooth, effects, you'd have to increase the
size of a single file by a factor of the amount of time you're looking
at. To show an object moving through space over a minute, you need 60
objects at various points along the curve it describes. And at 1 frame
per second that'll still be nasty.

What's needed is a language for *describing* movements, rather than
explicitly drawing them. To explicitly draw each object at a point in
time would be a step backwards from what VRML represents. It seems to
me that VRML is about describing rather than drawing. So we need a
behavior description language.

Now, we've avoided reinventing the wheel to date, and I think there are
ways to avoid reinventing the wheel in this case as well.

I know of two languages that would work for this, Java and SafeTCL. There
are probably others.

James

James Waldrop (JLW3) \ [email protected] / Ubique, Inc.
Systems Administrator \ [email protected] / 657 Mission #601
http://www.ubique.com/ \ 415.896.2434 / San Francisco, CA