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PositionalAudioFilter.js
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PositionalAudioFilter.js
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export default class PositionalAudioFilter {
constructor(positionalAudio, onListenerTranslate) {
this.positionalAudio = positionalAudio;
this.filter = positionalAudio.context.createBiquadFilter();
const ctx = this.positionalAudio.context;
this.filter.type = 'lowpass';
this.filter.frequency.setValueAtTime(22050, ctx.currentTime);
this.filter.Q.setValueAtTime(4, ctx.currentTime);
this.filter.gain.setValueAtTime(0.25, ctx.currentTime);
this.minFreq = 100;
this.maxFreq = 22050;
this.onListenerTranslate = onListenerTranslate;
}
get type() {
return this.filter.type.value;
}
set type(value) {
this.filter.type = value;
}
get frequency() {
return this.filter.frequency.value;
}
set frequency(value) {
this.filter.frequency.setValueAtTime(value,
this.positionalAudio.context.currentTime);
}
get Q() {
return this.filter.Q.value;
}
set Q(value) {
this.filter.Q.setValueAtTime(value,
this.positionalAudio.context.currentTime);
}
get gain() {
return this.filter.gain.value;
}
set gain(value) {
this.filter.gain.setValueAtTime(value,
this.positionalAudio.context.currentTime);
}
connect() {
this.positionalAudio.setFilter(this.filter);
}
disconnect() {
this.positionalAudio.removeFilter(this.filter);
}
update() {
const { positionalAudio } = this;
const camera = positionalAudio.listener.parent;
const mesh = positionalAudio.parent;
const distance = camera.position.distanceTo(mesh.position);
const value = this._calculateValue(distance);
if (isNaN(value)) return;
// Rescale value using min/max freq
const { minFreq, maxFreq } = this;
const scaledValue = value * (maxFreq - minFreq) + minFreq;
this.filter.frequency.setValueAtTime(scaledValue, positionalAudio.context.currentTime);
}
_calculateValue(distance) {
const { positionalAudio } = this;
const distanceModel = positionalAudio.getDistanceModel();
const refDistance = positionalAudio.getRefDistance();
const rolloffFactor = positionalAudio.getRolloffFactor();
switch (distanceModel) {
case 'linear':
const maxDistance = positionalAudio.getMaxDistance();
return 1 - rolloffFactor * (distance - refDistance) / (maxDistance - refDistance);
case 'inverse':
return refDistance / (refDistance + rolloffFactor * (Math.max(distance, refDistance) - refDistance));
case 'exponential':
return Math.pow(Math.max(distance, refDistance) / refDistance, -rolloffFactor);
}
}
}