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diff --git a/src/moof/interpolator.hh b/src/moof/interpolator.hh
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+
+/*]  Copyright (c) 2009-2010, Charles McGarvey  [**************************
+**]  All rights reserved.
+*
+* vi:ts=4 sw=4 tw=75
+*
+* Distributable under the terms and conditions of the 2-clause BSD license;
+* see the file COPYING for a complete text of the license.
+*
+**************************************************************************/
+
+#ifndef _MOOF_INTERPOLATOR_HH_
+#define _MOOF_INTERPOLATOR_HH_
+
+/**
+ * \file interpolator.hh
+ * Functions and classes concerning interpolations between values.
+ */
+
+#include <moof/math.hh>
+
+
+namespace moof {
+
+
+/**
+ * Interpolators should inherit from this base class to get some free
+ * functionality.  Subclasses of this base class will implement their own
+ * interpolation functions.
+ */
+template <class F, class T = scalar>
+class interpolator
+{
+public:
+
+	/**
+	 * Interpolation mode.
+	 */
+	enum mode
+	{
+		stop		= 0,	/// Interpolator will stop when done.
+		repeat		= 1,	/// Interpolator will go back to the beginning.
+		oscillate	= 2		/// Interpolator will reverse direction.
+	};
+
+
+	/**
+	 * Construct an uninitialized interpolator.
+	 */
+	interpolator() :
+		is_done_(true) {}
+
+	/**
+	 * Construct an interpolator.
+	 * \param a The initial value.
+	 * \param b The target value.
+	 * \param t The duration of the interpolation.
+	 * \param mode The interpolation mode.
+	 */
+	interpolator(const T& a, const T& b, scalar t = 1.0, mode mode = stop) :
+		state_(a),
+		prior_(a),
+		a_(a),
+		b_(b),
+		alpha_(SCALAR(0.0)),
+		scale_(SCALAR(1.0) / t),
+		mode_(mode),
+		is_done_(false) {}
+
+	/**
+	 * Initialize the interpolator.  Any interpolation already being
+	 * tracked by this object will be replaced with a new interpolation
+	 * based on the initialization arguments.
+	 * \param a The initial value.
+	 * \param b The target value.
+	 * \param t The duration of the interpolation.
+	 * \param mode The interpolation mode.
+	 */
+	void init(const T& a, const T& b, scalar t = 1.0, mode mode = stop)
+	{
+		a_ = a;
+		b_ = b;
+		alpha_ = 0.0;
+		scale_ = 1.0 / t;
+		mode_ = mode;
+		is_done_ = false;
+	}
+
+
+	/**
+	 * Update the interpolation state with a timeslice.
+	 * \param t The total time in seconds.
+	 * \param dt The number of seconds passed since the last call to
+	 * update.
+	 */
+	void update(scalar t, scalar dt)
+	{
+		if (!is_done_)
+		{
+			alpha_ += dt * scale_;
+			prior_ = state_;
+			state_ = function_(a_, b_, alpha_);
+
+			if (alpha_ > 1.0)
+			{
+				switch (mode_)
+				{
+					case stop:
+						alpha_ = SCALAR(1.0);
+						is_done_ = true;
+						break;
+					case repeat:
+						alpha_ -= SCALAR(1.0);
+						break;
+					case oscillate:
+						alpha_ = SCALAR(2.0) - alpha_;
+						scale_ = -scale_;
+						break;
+				}
+			}
+			else if (alpha_ < 0.0)
+			{
+				switch (mode_)
+				{
+					case stop:
+						alpha_ = SCALAR(0.0);
+						is_done_ = true;
+						break;
+					case repeat:
+						alpha_ += SCALAR(1.0);
+						break;
+					case oscillate:
+						alpha_ = -alpha_;
+						scale_ = -scale_;
+						break;
+				}
+			}
+		}
+	}
+
+
+	/**
+	 * Get the interpolated value.
+	 * \return The interpolated value.
+	 */
+	T state() const
+	{
+		return state_;
+	}
+
+	/**
+	 * Get the interpolated value interpolated between two updates.
+	 * \param alpha The fraction between updates.
+	 * \return The interpolated value.
+	 */
+	T state(scalar alpha) const
+	{
+		return lerp(prior_, state_, alpha);
+	}
+
+	/**
+	 * Get whether or not the interpolation is done.  This will only return
+	 * true if the interpolation mode is stop.
+	 * \return True if the interpolation has finished.
+	 */
+	bool is_done() const
+	{
+		return is_done_;
+	}
+
+
+private:
+
+	T	state_;
+	T	prior_;
+	T	a_;
+	T	b_;
+
+	F	function_;
+
+	scalar	alpha_;
+	scalar	scale_;
+	mode	mode_;
+	bool	is_done_;
+};
+
+
+struct linear_interpolation_function
+{
+	template <class T>
+	T operator () (const T& a, const T& b, scalar alpha)
+	{
+		return lerp(a, b, alpha);
+	}
+};
+
+
+typedef interpolator<linear_interpolation_function> lerp_scalar;
+
+
+} // namespace moof
+
+#endif // _MOOF_INTERPOLATOR_HH_
+