[Openal-devel] AL_SOURCE_RELATIVE

[Richard Furse]

Hi there - I'm a bit confused about what AL_SOURCE_RELATIVE is supposed to
do. Does it just pretend that the listener is at <0,0,0> for the rest of
processing? This is what I'd thought.

The annotated documentation for 1.0 says that:

	SOURCE_RELATIVE does not affect velocity or orientation calculation.

However, the 1.1 spec says that this:

	. indicates that the position, velocity, cone and direction
properties of a source are to be interpreted relative to the listener
position.

Specifically:
*	Should the listener orientation information be disabled when
AL_SOURCE_RELATIVE is enabled? i.e. should the coordinate flip back to the
default up=<0,1,0>, at=<0,0,-1>? I had guessed the answer here is no.
*	Should the listener's velocity be modelled as zero for the rest of
processing? I had guessed the answer here is no.
*	If the listener is at <0,0,-100> and the source is at <0,0,-50> with
velocity <0,0,100> and AL_SOURCE_RELATIVE is OFF, then the source is in
front of the listener, travelling outwards. If AL_SOURCE_RELATIVE is then
switched on and this is equivalent to setting the listener to <0,0,0>, then
the source goes behind the listener, travelling inwards. Is this right?
*	I'm guessing whatever rule applies for the velocities also applies
to cone vectors etc.

Sorry if this is a FAQ...

--Richard
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