[music-dsp] re: casting rays into a virtual environment

Ramy Sadek sadek at ict.usc.edu
Wed Feb 15 20:37:08 EST 2006


Hi Knut, 

You may be interested to read Professor Tom Funkhouser's papers which
describe a method for generating impulse responses from ray-casting. You
can find them, as well as an overview page here :
http://www.cs.princeton.edu/%7Efunk/acoustics.html

Also, at DAFX 2003, there was an article on fast beam tracing using dual
space computations, that could help speed up your ray casting. The paper
was titled "Sound Spatialization based on fast beam tracing in the dual
space" by M Foco et all.  Here's a link to scholar.google search. 

http://scholar.google.com/scholar?q=author:"Foco"%20intitle:"Sound%20Spa
tialization%20based%20on%20fast%20beam%20tracing%20in%20the%20..."%20&hl
=en&lr=

Best, 

Ramy Sadek
-----Original Message-----
From: music-dsp-bounces at shoko.calarts.edu
[mailto:music-dsp-bounces at shoko.calarts.edu] On Behalf Of Nils Schneider
Sent: Wednesday, February 15, 2006 4:31 AM
To: music-dsp
Subject: Re: [music-dsp] re: casting rays into a virtual environment

Hello Knut,

> Are you processing the entire wav file or am I missing something?

Yes at the moment I'm processing the entire wave file.

> If you are, did you consider just generating an Impulse Response? Then
> you could leave the actual reverb processing to optimized software
> that does this very well.

Yes I would really like to do that, but I don't know where to get such a
starting impulse from. Any links would be appreciated.

> Also, at what threshold do you cut the processing? For a given number
> of reflections, or when the amplitude dips below a threshold or what?

Exactly, I use both criterias, both are adjustable or can be disabled.

> I believe that for very accurate ray-tracing, you may need to do
> multiple passes for each frequency (octave bands?), and generate new
> rays (ray-lets?) at diffraction points. This means an insane number of
> reflections/rays for a 1-second delay-time.

Yes you're right. At the moment, I already run into problems when
generating two new rays for every reflection, it takes minutes until the
processing is completed for a very short file. I'll try it with the
generation of impulse responses only...

Nils

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