From: bobp@hal.com (Bob Pendelton)
Subject: Re: TECH: OIFF an object interchange file format
Date: Tue, 18 Aug 1992 15:56:48 GMT
Organization: HaL Computer Systems, Inc.



From article <1992Aug17.063857.24154@u.washington.edu>, by
vorl@sdf.lonestar.org (Omar Loggiodice):

> +-------------------------------------------------------------------------+
> |                     PROGRESS REPORT#2 FOR WE PROJECT                    |
> |                             START-UP VERSION                            |
> +-------------------------------------------------------------------------+

>    PLG format
>    ----------
> 
>      The version of PLG that we use is the following, numbers can be
>      represented in binary or ASCII format depending on the type of the OIFF
>      file.
> 
>      header:
>        <32b.#vertices>
>        <32b.#polygons>
> 
>      vertices:
> 
>        <32b.x#1>
>        <32b.y#1>     As many triplets as specified in the header
>        <32b.z#1>
>        ..
>        ..
>        <32b.x#n>
>        <32b.y#n>
>        <32b.z#n>
> 
> 
>      polygons:
> 
>        <32b.color>
>        <32b.#vertices>
>        <32b.vertex#1>
>        <32b.vertex#2>
>        ..
>        ..
>        <32b.vertex#n>


Perhaps you've left out a lot of details in this posting. But, as
presented, this format leave out a lot of information that should be
present, or at least be allowed for by the format.

First off, polygons have two faces. Each face needs a separate color.
Color blending requires a color per vertex per face. 

While we're on the subject of color, how do you specify it? The only
examples in the post show simple integers in the range 0 to 255.  Are
you assuming a standard predefined color map? You allow 32 bits for
color, how is it interpreted? 30 bit RGB?

You need to know which polygon face is which. Is there an implicit
ordering of the vertices that can be used to determine which way the
polygons are facing? Or is there a normal specifier that is not
described in your posting? Normals per vertex are needed for some
shading schemes.

				Bob P.
-- 
Bob Pendleton             | As an engineer I hate to hear:
bobp@hal.com              |   1) You've earned an "I told you so."
Speaking only for myself. |   2) Our customers don't do that.
                   <<< Odin, after the well of Mimir. >>>