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diff --git a/source/core/StarPeriodicFunction.hpp b/source/core/StarPeriodicFunction.hpp
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+#ifndef STAR_PERIODIC_FUNCTION_HPP
+#define STAR_PERIODIC_FUNCTION_HPP
+
+#include "StarInterpolation.hpp"
+#include "StarRandom.hpp"
+
+namespace Star {
+
+// Repeating, periodic function with optional period and magnitude variance.
+// Each cycle of the function will randomize the min and max values of the
+// function by the magnitude variance, and the period by the period variance.
+// Can approximate a randomized sin wave, triangle wave, square wave, etc based
+// on the weight operator provided to the value method.
+template <typename Float>
+class PeriodicFunction {
+public:
+  PeriodicFunction(
+      Float period = 1, Float min = 0, Float max = 1, Float periodVariance = 0, Float magnitudeVariance = 0);
+
+  void update(Float delta);
+
+  template <typename WeightOperator>
+  Float value(WeightOperator weightOperator) const;
+
+private:
+  Float m_halfPeriod;
+  Float m_min;
+  Float m_max;
+  Float m_halfPeriodVariance;
+  Float m_magnitudeVariance;
+
+  Float m_timerMax;
+  Float m_timer;
+  Float m_source;
+  Float m_target;
+  bool m_targetMode;
+};
+
+template <typename Float>
+PeriodicFunction<Float>::PeriodicFunction(
+    Float period, Float min, Float max, Float periodVariance, Float magnitudeVariance) {
+  m_halfPeriod = period / 2;
+  m_min = min;
+  m_max = max;
+  m_halfPeriodVariance = periodVariance / 2;
+  m_magnitudeVariance = magnitudeVariance;
+
+  m_timerMax = m_halfPeriod;
+  m_timer = 0;
+  m_source = m_max + Random::randf(-1, 1) * m_magnitudeVariance;
+  m_target = m_min + Random::randf(-1, 1) * m_magnitudeVariance;
+  m_targetMode = true;
+}
+
+template <typename Float>
+void PeriodicFunction<Float>::update(Float delta) {
+  m_timer -= delta;
+
+  // Only bring the timer forward once, rather than doing this in a loop.  This
+  // makes the function behave somewhat differently than it would for deltas
+  // which are greater than the period, but it avoids infinite looping
+  if (m_timer <= 0.0f) {
+    m_source = m_target;
+    m_target = (m_targetMode ? m_max : m_min) + Random::randf(-1, 1) * m_magnitudeVariance;
+    m_targetMode = !m_targetMode;
+    m_timerMax = m_halfPeriod + Random::randf(-1, 1) * m_halfPeriodVariance;
+    m_timer = max(0.0f, m_timer + m_timerMax);
+  }
+}
+
+template <typename Float>
+template <typename WeightOperator>
+Float PeriodicFunction<Float>::value(WeightOperator weightOperator) const {
+  // This is inverted, m_timer goes from m_timerMax to 0 as the value should go
+  // from m_source to m_target
+  auto wvec = weightOperator(m_timer / m_timerMax);
+  return m_target * wvec[0] + m_source * wvec[1];
+}
+
+}
+
+#endif