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/*
* Copyright 2010 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;
import com.jsyn.ports.UnitInputPort;
import com.jsyn.ports.UnitVariablePort;
/**
* Output approaches Input exponentially and will reach it in the specified time.
*
* @author Phil Burk (C) 2010 Mobileer Inc
* @version 016
* @see LinearRamp
* @see AsymptoticRamp
* @see ContinuousRamp
*/
public class ExponentialRamp extends UnitFilter {
public UnitInputPort time;
public UnitVariablePort current;
private double target;
private double timeHeld = 0.0;
private double scaler = 1.0;
public ExponentialRamp() {
addPort(time = new UnitInputPort("Time"));
input.setup(0.0001, 1.0, 1.0);
addPort(current = new UnitVariablePort("Current", 1.0));
}
@Override
public void generate(int start, int limit) {
double[] outputs = output.getValues();
double currentInput = input.getValues()[0];
double currentTime = time.getValues()[0];
double currentValue = current.getValue();
if (currentTime != timeHeld) {
scaler = convertTimeToExponentialScaler(currentTime, currentValue, currentInput);
timeHeld = currentTime;
}
// If input has changed, start new segment.
// Equality check is OK because we set them exactly equal below.
if (currentInput != target) {
scaler = convertTimeToExponentialScaler(currentTime, currentValue, currentInput);
target = currentInput;
}
if (currentValue < target) {
// Going up.
for (int i = start; i < limit; i++) {
currentValue = currentValue * scaler;
if (currentValue > target) {
currentValue = target;
scaler = 1.0;
}
outputs[i] = currentValue;
}
} else if (currentValue > target) {
// Going down.
for (int i = start; i < limit; i++) {
currentValue = currentValue * scaler;
if (currentValue < target) {
currentValue = target;
scaler = 1.0;
}
outputs[i] = currentValue;
}
} else if (currentValue == target) {
for (int i = start; i < limit; i++) {
outputs[i] = target;
}
}
current.setValue(currentValue);
}
private double convertTimeToExponentialScaler(double duration, double source, double target) {
double product = source * target;
if (product <= 0.0000001) {
throw new IllegalArgumentException(
"Exponential ramp crosses zero or gets too close to zero.");
}
// Calculate scaler so that scaler^frames = target/source
double numFrames = duration * getFrameRate();
return Math.pow((target / source), (1.0 / numFrames));
}
}
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