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diff --git a/src/main/java/com/jsyn/unitgen/ContinuousRamp.java b/src/main/java/com/jsyn/unitgen/ContinuousRamp.java
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+/*
+ * Copyright 2009 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;
+
+/**
+ * A ramp whose function over time is continuous in value and in slope. Also called an "S curve".
+ * 
+ * @author Phil Burk (C) 2009 Mobileer Inc
+ * @version 016
+ * @see LinearRamp
+ * @see ExponentialRamp
+ * @see AsymptoticRamp
+ */
+public class ContinuousRamp extends UnitFilter {
+    public UnitVariablePort current;
+    /**
+     * Time it takes to get from current value to input value when input is changed. Default value
+     * is 1.0 seconds.
+     */
+    public UnitInputPort time;
+    private double previousInput = Double.MIN_VALUE;
+    // Coefficients for cubic polynomial.
+    private double a;
+    private double b;
+    private double d;
+    private int framesLeft;
+
+    /* Define Unit Ports used by connect() and set(). */
+    public ContinuousRamp() {
+        addPort(time = new UnitInputPort(1, "Time", 1.0));
+        addPort(current = new UnitVariablePort("Current"));
+    }
+
+    @Override
+    public void generate(int start, int limit) {
+        double[] outputs = output.getValues();
+        double[] inputs = input.getValues();
+        double currentTime = time.getValues()[0];
+        double currentValue = current.getValue();
+        double inputValue = currentValue;
+
+        for (int i = start; i < limit; i++) {
+            inputValue = inputs[i];
+            double x;
+            if (inputValue != previousInput) {
+                x = framesLeft;
+                // Calculate coefficients.
+                double currentSlope = x * ((3 * a * x) + (2 * b));
+
+                framesLeft = (int) (getSynthesisEngine().getFrameRate() * currentTime);
+                if (framesLeft < 1) {
+                    framesLeft = 1;
+                }
+                x = framesLeft;
+                // Calculate coefficients.
+                d = inputValue;
+                double xsq = x * x;
+                b = ((3 * currentValue) - (currentSlope * x) - (3 * d)) / xsq;
+                a = (currentSlope - (2 * b * x)) / (3 * xsq);
+                previousInput = inputValue;
+            }
+
+            if (framesLeft > 0) {
+                x = --framesLeft;
+                // Cubic polynomial. c==0
+                currentValue = (x * (x * ((x * a) + b))) + d;
+            }
+
+            outputs[i] = currentValue;
+        }
+
+        current.setValue(currentValue);
+    }
+}