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