Re: [Flightgear-devel] FG - FGFX class

[Maik J. <mj...@gm...>]

Hi Erik,

Erik Hofman schrieb am 23.10.2008 18:47:
> Vladimir Karmishin wrote:
>
>   
>> I need any thoughts,
>> imaginations about which way can it be modified to let it work with  
>> multiple 3d sound emitters.
>>     
>
> Reading this again there might be some confusion; aircraft can have 
> multiple 3d sound emitters already, they are just tied to the main 
> aircraft right now (and the listener is always facing the main model, 
> this is probably why doppler doesn't function too well).
>
>   
no. The Doppler problems are due to OpenAL bugs and limitations. On most 
systems (at least at all which are using Open AL software Doppler 
calculation) I got strange effects. On Linux systems a workaround was to 
use only the relative velocity of listener and sound, which is 
physically not correct. But on windows even this approach results is 
strange effects. There I use my own software implementation in simgear 
and pass the calculated pitch and volume to Open AL. But Open AL clamps 
the pitch factor (If I remember correctly to 0.5 ... 2), and 
additionally many aircrafts modify the pitch by them self. This limits 
the Doppler effect in Flightgear.

Melchior sent me a note, that actual Open AL might be less buggy, but he 
still noticed strange effects.
> But you can already define the position an direction of each sound effect.
>   
Yes, and many aircrafts make use of this, e. g. the S58 or the Bo105.
> The remaining problem is to make the AI models also emit sound effects.
>
> Erik
>
>   
Maik