[sdiy] Music

[Scott Nordlund]

There is a 2D raytracing program for synthesizing reverb impulse 
responses, Voxengo's Impulse Modeler.  To get a really high quality 
sound, it needs to be run for a huge number of iterations and this 
takes a long time.  I'm not sure if it's doing something fancy to 
calculate reflections or what...

Surprisingly, the 2D thing isn't as big a limitation as you'd think. 
It sounds ok and is much easier to design a "room".

Static impulse responses are ok, but it would still be preferable 
to be able to do it in real time to, say, dynamically change the
position of the "performer" or "listener", as you'd have in an 
actual unamplified performance.  Not to mention moving the walls 
all over the place, stadium sized Leslie speakers...

Anyway I don't know of any other raytracing based reverb.  It's
been proposed but only in a theoretical "I wish this was practical"
kind of way.

----------------------------------------
> Date: Tue, 20 Jul 2010 18:14:43 +0200
> From: thomas at pdp7.org
> To: synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] Music
>
> Am 7/20/10 17:55 , schrieb Scott Nordlund:
>> I've read some about modeling spring and plate reverbs. High order
>> dispersion filters are very important but it takes a lot of CPU power.
>> I'd assume that's true of cymbals and gongs and things too. Also,
>> trying to emulate a 2 or 3 dimensional acoustic space with 1D
>> waveguides isn't ideal. I think the "proper" way to do it would be ray
>> tracing, not that it's remotely possible in real time. There's
>> probably some easier compromise that gets passable results, though.
>> After all, most reverb algorithms make no attempt to actually model an
>> acoustic process. They only make a lazy approximation that's fine
>> tuned to sound reasonable.
>
> Raytracing for graphics is possible in realtime even on a CPU and has
> been done successfully for some 10 years now. I imagine the only objects
> needed for a reverb "scene" would be quads that bound the space in which
> the reverb is to be sampled. Kind of like they did with actual rooms, a
> loudspeaker, and a microphone in studios. Do I miss something that would
> make raytracing impractical for this use case?
>
> Thomas
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