Stephen J Baker wrote:
> So, why are the lines in the RedBook image (Plate 20) straight?
>
> Well, I don't believe that picture in the book was really rendered by
> OpenGL.
>
> Some of the pictures in the first revision of RedBook were done in IrisGL
> and some by SGI's Performer library - which hadn't (AFAIK) been ported to
> OpenGL by the time the RedBook was printed.
> In IrisGL, the MIPmaps (if implemented) were computed inside the IrisGL
> API, (unlike OpenGL where you can build your own MIPmaps) so it would be
> impossible to do the trick of colouring each level of map differently
> if you were rendering that image in IrisGL.
>
> So, I strongly suspect that the picture in plate 20 is faked by a set of
> differently coloured rectangles rather than as a single textured polygon.
>
> I can't prove that though.
Sorry Steve, I just had to test this out. :-)
I ran the mipmap.c program on my IMPACT, IR and O2 systems and saw
straight transition lines. However, the the transition lines on the IR
and O2 were actually a bit ragged - a few pixels getting different
texels than their vertical neighbors. Hmmm.
> Anyway - I think Mesa does it right - so don't sweat it.
Nobody has complained so it's probably close enough.
-Brian
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Brian Paul Avid Technology / Softimage [EMAIL PROTECTED]
