[Openal] Directional source

[Garin Hiebert]

You'll probably want to grab some graph paper and map the models out 
yourself, but here's the quickie explanation of the parameters for all 
the models:

For all *_CLAMPED versions:

-- distances above AL_MAX_DISTANCE get the gain at distance = 
AL_MAX_DISTANCE
-- distances below AL_REFERENCE_DISTANCE get the gain at distance = 
AL_REFERENCE_DISTANCE

For the inverse distance model:

AL_ROLLOFF_FACTOR -- sets the slope ( default is 1 -- going larger 
increases the slope, going lower decreases the slope)
AL_REFERENCE_DISTANCE -- the point where the gain is 1
AL_MAX_DISTANCE -- no influence unless using the clamped version of this 
model

For the linear model:

AL_ROLLOFF_FACTOR -- sets the slope
AL_REFERENCE_DISTANCE -- the point where the gain is 1
AL_MAX_DISTANCE -- the point where the gain becomes zero

For the exponential model:

AL_ROLLOFF_FACTOR -- sets the formula used to determine the slope
        -- the default of 1 gives the same slope as the default inverse 
distance model (1/x), 2 would be a 1/x^2 model (physically realistic), etc.
AL_REFERENCE_DISTANCE -- the point where the gain is 1
AL_MAX_DISTANCE -- no influence unless using the clamped version of the 
model


In summary:

The reference distance is used everywhere to determine where the gain 
should be at unity.  The rolloff factor affects how steep the falloff is 
going to be from the reference distance.  The max distance -- if it has 
an influence -- is either used as a clamp or sets where the gain becomes 
zero (linear model only).

Garin



Garin