Re: standard coordinate systems & units of measure

Kevin Goldsmith (
Mon, 29 Aug 1994 00:47:51 -0700 (PDT)

> As an object designer, you have the ability
> to bundle interfaces to some useful coordinate systems with your object,
> and can provide whichever ones you feel like supporting (hopefully at least
> the "standard" one, once we all agree on it :) ). As an object user, if
> the object comes ready with the coordinate system you want to use, great!
> Otherwise, you have use a standard conversion, provide it yourself, or use
> someone else's object.

that was my point. There is no need to standardize several
different coordinate systems. As long as there is one standard
one, object designers can provide the necessary convertions from their
"special" coordinate systems.

> You wouldn't: these are special-case coordinate systems that are
> nonetheless useful enough that they might be worth supporting. (Pictures
> are almost always hung on a wall, right?) Or not. Maybe other coordinate
> systems will be popular.
Can you describe a coordinate system that puts a picture against
a wall? :)

[example omitted]
> The idea here is not to limit people in where they're allowed to put
> objects, or to save FPU cycles (as a few people seemed to think), but to
> save object-placement time. I'm assuming (not having done it myself) that,
> no matter your choice of user interface, it's somewhat tedious to have to
> convert to the right coordinate system, rotate, scale, and precisely line
> up hundreds or perhaps thousands of objects to create a scene. So, in the
> admittedly limited cases where the object designers can help out with the
> boring stuff, it would be a win to give them a mechanism to do so.
Having done this very often, I can tell you that it is easier to
design objects in a standard coordinate system and then place them into
your scene which is also in a standard coordinate system. Using one
coordinate system drastically aids in re-use as well. Also, I must point
out that the whole reason that user interfaces exist are to shield users
(designers) from all that low-level stuff. If you are using a program
whose user interface makes it hard to do what you want, you need to
switch programs.

> (That being said, I'll defer to the judgement of those more experienced in
> computer graphics than I. I'm subscribed only to the digest list, so
> please cc: responses directly. Thanks.)
I think you might want to get some of your hands on some
different modelling programs, if possible, to see how they work. You
might also want to check out Foley, Van Dam, etc... to see how they
explain different coordinate spaces and mapping between them in computer


> | Brian Slesinsky | | (work) |