dpeacock at creativelabs.com
Mon Mar 31 13:49:47 PDT 2008
When you enable Source Relative mode on a Source its Position, Velocity
and Orientation all become relative to the Listener's parameters rather
than absolute values. It is as if the Listener is positioned at 0,0,0
with a velocity of 0,0,0 and an orientation of 0,0,-1,0,1,0 (at then up).
Changing the Listeners position, velocity, and orientation will have no
impact on a Source Relative Source.
>> If the listener is at <0,0,-100> and the source is at <0,0,-50> with
>>and AL_SOURCE_RELATIVE is OFF, then the source is in front of the
Assuming the default orientation for the Listener (0,0,-1,0,1,0) the Source
is actually behind the listener and is travelling away from it.
>>If AL_SOURCE_RELATIVE is then switched on and this is equivalent to
>>the listener to <0,0,0>, then the source goes behind the listener,
travelling inwards. Is this right?
With Relative Mode on, the Source is in-front of the listener and
travelling towards it.
Creative Labs, Inc.
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<rf015d9821 at bluey
Sent by: <openal-devel at opensource.creative.c
ces at opensource.cr cc
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
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
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
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...
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