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/*
* Copyright 2011 Phil Burk, Mobileer Inc
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.jsyn.unitgen;
/**
* An envelope that can be used in a GrainFarm to shape the amplitude of a Grain. The envelope
* starts at 0.0, rises to 1.0, then returns to 0.0 following a cosine curve.
*
* <pre>
* output = 0.5 - (0.5 * cos(phase))
* </pre>
*
* @author Phil Burk (C) 2011 Mobileer Inc
* @see GrainFarm
*/
public class RaisedCosineEnvelope extends GrainCommon implements GrainEnvelope {
protected double phase;
protected double phaseIncrement;
public RaisedCosineEnvelope() {
setFrameRate(44100);
setDuration(0.1);
}
/**
* @return next value of the envelope.
*/
@Override
public double next() {
phase += phaseIncrement;
if (phase > (2.0 * Math.PI)) {
return 0.0;
} else {
return 0.5 - (0.5 * Math.cos(phase)); // TODO optimize using Taylor expansion
}
}
/**
* @return true if there are more envelope values left.
*/
@Override
public boolean hasMoreValues() {
return (phase < (2.0 * Math.PI));
}
/**
* Reset the envelope back to the beginning.
*/
@Override
public void reset() {
phase = 0.0;
}
@Override
public void setDuration(double duration) {
phaseIncrement = 2.0 * Math.PI / (getFrameRate() * duration);
}
}
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