Vertex submission (was Re: [Plib-devel] Re: 3DNow! acceleration)

[Sam S. <sa...@sp...>]

-----Original Message-----
From: Steve Baker <sjb...@ai...>
To: pli...@li... <pli...@li...>
Date: 02 April 2000 21:00
Subject: Re: [Plib-devel] Re: 3DNow! acceleration


>Sam Stickland wrote:
>
>> Surely to do the field of view cull you have to transform every vertex in
>> the scene by the modelview matrix?
>
>No - I only cull using bounding spheres - and only at the level of
>entire ssgLeaf nodes.
>
>There is no point in culling down to the individual polygon level
>because OpenGL is already doing that - and possibly can use hardware
>to accellerate that process.


Yes, that makes a lot of sense now I actually stop to think about it.. :)

>>  Isn't this the sort of thing that 3DNow!
>> could really speed up?
>
>If I did that - then you'd be right - and 3DNow! would be important.
>
>...but I don't so you aren't and it isn't.  :-)


Heh..

>> AMD provide code to detect whether 3DNow! acceleration is supported (this
>> works on all x86 processors), as well as code to detect MMX and SSE
>> instructions.  Turning it off on non x86 processors could be easily done
as
>> a compile time option, although I'm sure there are ways of detecting this
at
>> run-time (but that's probably a bit of a kludge).
>
>But there is still the issue of how to assemble that code portably.
>
>There are two different (and incompatible) assemblers for Linux/x86 and
>yet a different syntax for Windoze - then some of the older versions of
>those assemblers don't know about the 3DNow mnemonics.   I see the hassles
>Mesa has been having with this - and I don't want to follow in their
>footsteps unless there is a HUGE benefit in so doing.


OK...

How about how the vertexes are submitted?  Am I right in thinking that
currently ssgVTable simply does glBegin's and glEnd's on the vertex
information?  I assume there could be some big wins here if we started using
CVA's (or even just vertex arrarys?) ?.

Or is the idea for people to create subclasses of VTable to fix the
situations as neccessary?

Sam