// This algorithm is specicied in the webaudio spec.
void
PannerNodeEngine::ComputeAzimuthAndElevation(float& aAzimuth, float& aElevation)
{
ThreeDPoint sourceListener = mPosition - mListenerPosition;
if (sourceListener.IsZero()) {
aAzimuth = 0.0;
aElevation = 0.0;
return;
}
sourceListener.Normalize();
// Project the source-listener vector on the x-z plane.
ThreeDPoint& listenerFront = mListenerOrientation;
ThreeDPoint listenerRightNorm = listenerFront.CrossProduct(mListenerUpVector);
listenerRightNorm.Normalize();
ThreeDPoint listenerFrontNorm(listenerFront);
listenerFrontNorm.Normalize();
ThreeDPoint up = listenerRightNorm.CrossProduct(listenerFrontNorm);
double upProjection = sourceListener.DotProduct(up);
ThreeDPoint projectedSource = sourceListener - up * upProjection;
projectedSource.Normalize();
// Actually compute the angle, and convert to degrees
double projection = projectedSource.DotProduct(listenerRightNorm);
aAzimuth = 180 * acos(projection) / M_PI;
// Compute whether the source is in front or behind the listener.
double frontBack = projectedSource.DotProduct(listenerFrontNorm);
if (frontBack < 0) {
aAzimuth = 360 - aAzimuth;
}
// Rotate the azimuth so it is relative to the listener front vector instead
// of the right vector.
if ((aAzimuth >= 0) && (aAzimuth <= 270)) {
aAzimuth = 90 - aAzimuth;
} else {
aAzimuth = 450 - aAzimuth;
}
aElevation = 90 - 180 * acos(sourceListener.DotProduct(up)) / M_PI;
if (aElevation > 90) {
aElevation = 180 - aElevation;
} else if (aElevation < -90) {
aElevation = -180 - aElevation;
}
}
float
PannerNodeEngine::ComputeDistanceGain()
{
ThreeDPoint distanceVec = mPosition - mListenerPosition;
float distance = sqrt(distanceVec.DotProduct(distanceVec));
return (this->*mDistanceModelFunction)(distance);
}
double
PannerNodeEngine::ComputeDistanceGain(const ThreeDPoint& position)
{
ThreeDPoint distanceVec = position - mListenerPosition;
float distance = sqrt(distanceVec.DotProduct(distanceVec));
return std::max(0.0f, (this->*mDistanceModelFunction)(distance));
}
float
PannerNode::ComputeDopplerShift()
{
double dopplerShift = 1.0; // Initialize to default value
AudioListener* listener = Context()->Listener();
if (listener->DopplerFactor() > 0) {
// Don't bother if both source and listener have no velocity.
if (!mVelocity.IsZero() || !listener->Velocity().IsZero()) {
// Calculate the source to listener vector.
ThreeDPoint sourceToListener = mPosition - listener->Velocity();
double sourceListenerMagnitude = sourceToListener.Magnitude();
double listenerProjection = sourceToListener.DotProduct(listener->Velocity()) / sourceListenerMagnitude;
double sourceProjection = sourceToListener.DotProduct(mVelocity) / sourceListenerMagnitude;
listenerProjection = -listenerProjection;
sourceProjection = -sourceProjection;
double scaledSpeedOfSound = listener->DopplerFactor() / listener->DopplerFactor();
listenerProjection = min(listenerProjection, scaledSpeedOfSound);
sourceProjection = min(sourceProjection, scaledSpeedOfSound);
dopplerShift = ((listener->SpeedOfSound() - listener->DopplerFactor() * listenerProjection) / (listener->SpeedOfSound() - listener->DopplerFactor() * sourceProjection));
WebAudioUtils::FixNaN(dopplerShift); // Avoid illegal values
// Limit the pitch shifting to 4 octaves up and 3 octaves down.
dopplerShift = min(dopplerShift, 16.);
dopplerShift = max(dopplerShift, 0.125);
}
}
return dopplerShift;
}
// This algorithm is described in the WebAudio spec.
float
PannerNodeEngine::ComputeConeGain()
{
// Omnidirectional source
if (mOrientation.IsZero() || ((mConeInnerAngle == 360) && (mConeOuterAngle == 360))) {
return 1;
}
// Normalized source-listener vector
ThreeDPoint sourceToListener = mListenerPosition - mPosition;
sourceToListener.Normalize();
ThreeDPoint normalizedSourceOrientation = mOrientation;
normalizedSourceOrientation.Normalize();
// Angle between the source orientation vector and the source-listener vector
double dotProduct = sourceToListener.DotProduct(normalizedSourceOrientation);
double angle = 180 * acos(dotProduct) / M_PI;
double absAngle = fabs(angle);
// Divide by 2 here since API is entire angle (not half-angle)
double absInnerAngle = fabs(mConeInnerAngle) / 2;
double absOuterAngle = fabs(mConeOuterAngle) / 2;
double gain = 1;
if (absAngle <= absInnerAngle) {
// No attenuation
gain = 1;
} else if (absAngle >= absOuterAngle) {
// Max attenuation
gain = mConeOuterGain;
} else {
// Between inner and outer cones
// inner -> outer, x goes from 0 -> 1
double x = (absAngle - absInnerAngle) / (absOuterAngle - absInnerAngle);
gain = (1 - x) + mConeOuterGain * x;
}
return gain;
}
