Re: (Fwd) Re: bump mapping using Infinite Reality

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Brian Cabral (cabral++at++sgi.com)
Mon, 26 Aug 1996 08:39:21 -0700


> Date: Fri, 23 Aug 96 09:37:59 -0500
> From: steve++at++mred.bgm.link.com (Steve Baker)
> To: info-performer++at++sgi.com
> Subject: Re: bump mapping using Infinite Reality
>
> Angus said:
>
> > Brian Cabral rhowed me a real-time bump mapping implementation
> > a year ago running on RE2, this was also explained on a recent
> > SGI graphics course. He's now published a paper on a more
> > general shading approach which I haven't seen this).
>
> OK, I think I follow this explanation - but it's a typical
> 'rigged demo' approach. You end up having people believe that
> the machine can do something that is never going to work in
> most 'real' applications.
>

As the progenetor of the "rigged demo" :)) I thought some explanation
on what I was trying achieve is in order. I was striving to do pixel
wise correct bump mapping within the arithmetic precision of the frame
buffer. By correct I mean starting with Blinn's original formulation
and mathematically going forward. I achieved this using multi-pass
techniques. This was a non-trivial excerise but one which proved what
I wanted. Getting the answer right was the important aspect of the
demo.

As to whether you can use this type of bump mapping in a 60hz
real-time demo is orthogonal w.r.t. any multipass algorithm. If you
use this effect you get less fill and geometry for that part of the
scene. It's just another constraint on primarily your data base but
also your management of the frame buffer and graphics pipeline. So I
don't see that there's any smoke and mirrors here. Just another way to
use an already powerful graphics/imaging system in a way others may
not have tried or figured out.

                                B.c.
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