Re: [Algorithms] Spherical harmonics for room acoustic modelling

[Peter-Pike S. <pet...@ho...>]

Haven't read the whole thread, but here is a paper that will be presented at siggraph this year:
http://gamma.cs.unc.edu/PrecompWaveSim/
You would clearly need to scale back both memory usage and run-time to make this viable for games of course.
Peter-Pike

Date: Tue, 20 Jul 2010 17:13:06 +0100
From: ni...@gm...
To: gda...@li...
Subject: Re: [Algorithms] Spherical harmonics for room acoustic modelling

Actually I implemented a basic beam tree that used the material properties to estimate reverb in closed environments. The beam tree was too large for detailed outdoor environments, but I suppose if you have a decent mesh reduction algorithm you could scale it down, I just never had the time to finish this work.


Cheers,
-Ken Noland

On Sun, Jul 18, 2010 at 11:03 AM, Jon Watte <jw...@gm...> wrote:




 I'd have doubts you'd get good enough response time on CPU alone


Actually, the CPU can give you excellent response times if you're using a convolution based solution. DJBFFT is a very high performance, unencumbered convolution implementation, and it takes a minimal amount of CPU for a single sound stream. The problem comes when you want to combine delay lines to do overlap-add long convolution (or use the variable-window-size that's allegedly still patented by Lake DSP). It starts adding up! The GPU might be good at larger convolutions, but it has higher latency than the CPU.

I'm not sure Spherical Harmonics is the right solution. Sound reflection is a function of frequency mapping to absorption and directional spread. And whereas the eye is only sensitive to three separate frequencies, the ear is sensitive to thousands... And in SH based PRT, you often collapse the direction-dependent response into a single term, and filter the three frequencies using a separate RGB "diffuse reflectance" texture. If you applied the same to sound, you'd probably get a better than nothing, but you might only get good enough that the problems start to become obvious :-) (Bass, Mid and Treble, with a fixed reflectance function)


Sincerely,
jw

--
Americans might object: there is no way we would sacrifice our living standards for the benefit of people in the rest of the world. Nevertheless, whether we get there willingly or not, we shall soon have lower consumption rates, because our present rates are unsustainable. 






On Sat, Jul 17, 2010 at 2:23 PM, Oscar Forth <os...@tr...> wrote:


OK maybe not spherical harmonic based but gives the same sorta results and, therefore, just as interesting :)


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