Re: [Plib-devel] Re: 3DNow! acceleration

[Steve B. <sjb...@ai...>]

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.

>  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.  :-)

> 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.

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
sj...@ht...      (work)