Re: [Algorithms] Spherical harmonics for room acoustic modelling

[Samuel M. <sam...@go...>]

Somehow OT, I think what was missing in the video for the mentioned
siggraph paper (http://gamma.cs.unc.edu/PrecompWaveSim/), was some
sort of model for the human ear. I strongly suspect that for the
virtual recording they just placed two undirected virtual microphones
some 20cm apart, because with headphones it still sounded as though
every sound source was inside your head (Though the sense of space was
great). And I guess that's because in the virtual recording the
virtual external ear is missing, which is mainly responsible for
directional hearing in the real world. Just listen to these videos
(with earphones!) if you have no idea what I'm talking about (these
both model the external ear in some way, I'm not sure if they also
have real room acoustic modelling):

binaurial demonstration video:
http://www.youtube.com/watch?v=vfViBtIjK4c&feature=related <-- watch
out for the telephone ;)
virtual haircut: http://www.youtube.com/watch?v=8IXm6SuUigI&feature=related

Unfortunately there are very little details available publicly, and
those videos have been around for a long time, so I guess the research
around the subject somehow died.


BTW, I'm all for better, more sophisticated and computationally
expensive sound in games! Ego-shooters, horror games, how they could
benefit from the equivalent of the telephone above! ;)


Samuel


On Wed, Jul 21, 2010 at 8:39 PM, Peter-Pike Sloan
<pet...@ho...> wrote:
> 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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