Tone.js/Tone/component/Envelope.js

///////////////////////////////////////////////////////////////////////////////
//
//	Envelope
//
//	ADR envelope generator attaches to an AudioParam
///////////////////////////////////////////////////////////////////////////////

define(["Tone/core/Tone"], function(Tone){


	Tone.Envelope = function(attack, decay, sustain, release, audioParam, minOutput, maxOutput){
		//extend Unit
		Tone.call(this);

		//pass audio through
		this.input.connect(this.output);

		//set the parameters
		this.param = this.defaultArg(audioParam, this.input.gain);
		this.attack = this.defaultArg(attack, .01);
		this.decay = this.defaultArg(decay, .1);
		this.release = this.defaultArg(release, 1);
		this.sustain = this.defaultArg(.5);

		// this.setSustain(this.defaultArg(sustain, .1));
		this.min = this.defaultArg(minOutput, 0);
		this.max = this.defaultArg(maxOutput, 1);
		
		//set the initial value
		this.param.value = this.min;
	}

	Tone.extend(Tone.Envelope, Tone);

	//attack->decay->sustain
	Tone.Envelope.prototype.triggerAttack = function(time){
		var startVal = this.min;
		if (!time){
			startVal = this.param.value;
		}
		time = this.defaultArg(time, this.now());
		this.param.cancelScheduledValues(time);
		this.param.setValueAtTime(startVal, time);
		this.param.linearRampToValueAtTime(this.max, time + this.attack);
		var sustainVal = (this.max - this.min) * this.sustain + this.min;
		this.param.linearRampToValueAtTime(sustainVal, time + this.decay + this.attack);
	}

	//attack->decay->sustain
	Tone.Envelope.prototype.triggerAttackExp = function(time){
		var startVal = this.min;
		if (!time){
			startVal = this.param.value;
		}
		time = this.defaultArg(time, this.now());
		this.param.cancelScheduledValues(time);
		this.param.setValueAtTime(startVal, time);
		this.param.exponentialRampToValueAtTime(this.max, time + this.attack);
		var sustainVal = (this.max - this.min) * this.sustain + this.min;
		this.param.exponentialRampToValueAtTime(sustainVal, time + this.decay + this.attack);
	}

	//triggers the release of the envelope
	Tone.Envelope.prototype.triggerRelease = function(time){
		var startVal = this.param.value;
		if (time){
			startVal = (this.max - this.min) * this.sustain + this.min;
		}
		time = this.defaultArg(time, this.now());
		this.param.cancelScheduledValues(time);
		this.param.setValueAtTime(startVal, time);
		this.param.linearRampToValueAtTime(this.min, time + this.release);
	}


	//triggers the release of the envelope
	Tone.Envelope.prototype.triggerReleaseExp = function(time){
		var startVal = this.param.value;
		if (time){
			startVal = (this.max - this.min) * this.sustain + this.min;
		}
		time = this.defaultArg(time, this.now());
		this.param.cancelScheduledValues(time);
		this.param.setValueAtTime(startVal, time);
		this.param.exponentialRampToValueAtTime(this.min, time + this.release);
	}

	return Tone.Envelope;
});