Inventor file format

John W. Barrus (barrus@merl.com)
Tue, 21 Jun 1994 07:40:33 -0400

Brian Behlendorf <brian@wired.com> wrote:
>It might be that Inventor is too heavy-duty for our purposes - we want
>something so easy to parse that browsers for all platforms can be created
>without too much effort. Inventor might have a lot of pre-made code
>behind it, but if it's only on SGI platforms, and too complex for free
>browsers to be made for other platforms, that's a problem. And I don't
>expect SGI to be making an effort to port to other platforms, simply
>because their software and hardware come as a package.
>
> Brian

Inventor as a whole (library, utilities, viewers, etc.) would be a huge
effort to duplicate. However, the file format is well-defined and allows
an extensive list of data types or 'nodes'. I suggest that we look over
all of the nodes available in Inventor. Next, we decide which ones are the
most important to us. Then, we use the same syntax for our file formats.
Anything in the file that doesn't belong to the chosen list of nodes is
ignored by our file reader - which is easy to do with the Inventor file
format.

For instance, we might read in and display all of the geometry nodes using
the default material (colors) and lighting for a first pass. The second
version might use the material and lighting information and the third
generation might use the animation nodes. As long as we didn't ignore any
essential nodes for the first version of the display program, we would be
OK.

I don't agree that it is too complex for browsers to be made for other
platforms. I think it is extensive, but simple and straightforward.

I agree that we need a statement from SGI about using the file format, just
to make sure we aren't asking for trouble in the future. By the way, there
are several companies selling modelers which use the Inventor file format
and libraries. That fact makes me believe that we won't get any trouble
from SGI for promoting the OpenInventor data file format.

There are no distribution royalties for the SGI executables because every
SGI comes with Inventor run-time libraries. One easy way to start would be
to use an SGI to create the first Mosaic-like client using Inventor. That
executable and source could be freely distributed without royalties or
legal action.

John B.

-------------------------

John Barrus barrus@merl.com

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