[Korea-chapter] [X3D] Agenda items for the Korea chapter meeting (Wed. 5:10pm PST / Thu 9:10am Korea)

Don Brutzman brutzman at nps.edu
Thu Oct 15 07:29:09 PDT 2009

Justin Couch wrote:
> [...]
> Oh gees no! Don't do that! The whole point of a units specification is
> to create a real world equivalent for modeling purposes. Units are
> absolute, not relative. Make it relative and you'll never be able to
> compose worlds together of different scales. If the parent file is in
> millimetres and the child file is in kilometres, everything should
> render as you expect. If you applied a relative scale the contained file
> would look completely wrong.
> The specification should be absolutely silent on any concept of
> inter-file relationships. All units specifications must be absolute.

Well said, Justin, thanks.  Since parent scenes have no ability to
ensure that child scenes are maintained in the relative units expected,
the only practical solution is to keep unit definitions absolute.

After all, the scene author is stating "these are the required units for
this scene."

Browsers can no doubt optimize scaling appropriately when they compose
Inline and external prototype nodes within a single scene.

> And, because they are absolute, all the interfile issues are
> automatically resolved without needing any additional spec language.

umm that would be nice, and agreed with your intent, but we will probably
need to put some words in there to ensure that there is no misunderstanding.
saying just enough (but not too much) is the balance we always strive for.

all the best, Don
Don Brutzman  Naval Postgraduate School, Code USW/Br           brutzman at nps.edu
Watkins 270   MOVES Institute, Monterey CA 93943-5000 USA  work +1.831.656.2149
X3D, virtual worlds, underwater robots, XMSF  http://web.nps.navy.mil/~brutzman

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