[gameprogrammer] Re: Fixed Point Library at gameprogrammer.com
- From: David Olofson <david@xxxxxxxxxxx>
- To: gameprogrammer@xxxxxxxxxxxxx
- Date: Fri, 7 Dec 2007 23:25:30 +0100
On Friday 07 December 2007, Bob Pendleton wrote:
[...]
> What kind of machine still needs fixed point arithmetic?
PS2 and other consoles of similar age or older, pretty much anything
handheld (ARM CPUs and the like), and probably some other devices...
Some (like the PS2) do have 32 bit floating point support in the
hardware, but not 64 bit. Even if there is serious FP support in
theory, you cannot make use of it without platform specific code.
This is why I'm *still* not sure how much integer/fixed point support
there will be in Audiality 2. Do I care about these machines, or is
it ok if my games cannot realistically be ported to them?
Kobo Deluxe takes several *minutes* to render the sounds on some of
these platforms - sometimes just because of the 64 bit phase
accumulators in some oscillators, sometimes because there is floating
ponit DSP at all. The former shouldn't be a big job to fix, whereas
the latter requires a complete rewrite of all DSP code.
For now, I'm getting away with caching sounds to disk, but that only
works because the real time part of Audiality 0.1.x is actually just
a simple sampleplayer with some master effects. Even so, "several
minutes" is a long time to wait, even if it's just the first time you
start the game. And of course, it wastes disk space and works only
for games that don't need any dynamic real time synthesis. I think
it's a dead end, basically. This stuff belongs on high end PCs only.
I'm considering downgrading Kobo Deluxe to a simpler integer-only real
time synth ("SID on steroids" style) so it'll run well on low end
hardware, and then forgetting about all that and focus on PC style
hardware only for future projects. This integer/FP separation just
causes too much extra work, even though theoretically, the CPU power
is sufficient, at least for load-time rendering.
//David Olofson - Programmer, Composer, Open Source Advocate
.------- http://olofson.net - Games, SDL examples -------.
| http://zeespace.net - 2.5D rendering engine |
| http://audiality.org - Music/audio engine |
| http://eel.olofson.net - Real time scripting |
'-- http://www.reologica.se - Rheology instrumentation --'
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