[Openal] Listener positioning versus source positioning.
tri at tactile3d.com
Mon Aug 15 12:17:48 PDT 2005
Well, I'm pretty sure OpenAL does not implement doppler as it would
occur in a medium like
air, but rather uses something similar to the (simpler) doppler equation
for light. There is an
asymmetry if doing it properly, but the limit of both equations (light
and non-light) are the same
when the velocity is much smaller than the mediums propagation velocity.
It's something like: f' = f(1-v*cos(a))/(1-v^2)^0.5 for light (and OpenAL)
The cos(a) is for getting the component of the velocity along the line of hearing, between the
source and listener, and is therefore a function of BOTH listener and source positions. Even
using the more complex medium-based equation would need this.
Personally I think that an "audiological" reason is the ONLY good reason to do it like this... unlike
OpenGL (where, of course the speed of light is infinitely large and red and blue doppler shifts
do not enter the scene)
It is, after-all, an audio library ;)
Garin Hiebert wrote:
>> range attenuation going to be different through moving air for example?
> If so, I don't think any of the formulas used by any of the
> implementations of OpenAL (including the EAX-enhanced versions) take
> this into account. I'm counting on a colleage correcting me if I'm
> openal mailing list
> openal at opensource.creative.com
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