[Openal] EFX Clarifications 2

[Daniel PEACOCK]

Hi Christopher,

> Is it possible for someone in the know to lay out the exact order
> and application of the following properties for the effect slot,
> reverb effect, and source?

The exact formulas used for these properties are not available (they are
Creative IP).  All the properties except AL_EFFECTSLOT_GAIN are used to
control the send level from each Source to the Effect Slot (this is
completely different to what you wrote below).

> AL_EFFECTSLOT_AUXILIARY_SEND_AUTO
> AL_ROOM_ROLLOFF_FACTOR
> AL_REVERB_ROOM_ROLLOFF_FACTOR
> AL_AUXILIARY_SEND_FILTER_GAIN_AUTO
and AL_AUXILIARY_SEND_FILTER_GAINHF_AUTO

AL_EFFECTSLOT_AUXILIARY_SEND_AUTO is equivalent to the EAX 4.0 FX Slot
"Environment" flag.

When it is "off" (false) it means that a source's send signal to the effect
is the same as the signal sent to the dry path, minus Direct Filter Gain
and Gain HF and plus the Send Filter Gain and Gain HF.

When it is "on" a source's send signal is attenuated by 1) reverb
statistical model based on reverb decay time and source to listener
distance, 2) Room RollOff (summation of Reverb Room RollOff Factor and
Source Room RollOff Factor), 3) air absorption, and 4) source directivity
(cone parameters).

(1) is disabled if AL_AUXILIARY_SEND_FILTER_GAIN_AUTO is off (false)
(4) affect on low frequencies is disabled when
AL_AUXILIARY_SEND_FILTER_GAIN_AUTO is off (false), affect on high
frequencies is disabled when AL_AUXILIARY_SEND_FILTER_GAINHF_AUTO is off
(false).

> AL_EFFECTSLOT_GAIN

This is a global attenuation of the effect output.

Dan