Initial community commit

Src/external_dependencies/openmpt-trunk/tracklib/FadeLaws.h

@@ -0,0 +1,62 @@
+/*
+ * FadeLaws.h
+ * ----------
+ * Purpose: Various fade law implementations for sample and pattern fading / interpolation
+ * Notes  : (currently none)
+ * Authors: OpenMPT Devs
+ * The OpenMPT source code is released under the BSD license. Read LICENSE for more details.
+ */
+
+#pragma once
+
+#include "openmpt/all/BuildSettings.hpp"
+
+#include "mpt/base/numbers.hpp"
+#include <cmath>
+
+OPENMPT_NAMESPACE_BEGIN
+
+namespace Fade
+{
+	enum Law
+	{
+		kLinear,
+		kPow,
+		kSqrt,
+		kLog,
+		kQuarterSine,
+		kHalfSine,
+	};
+
+	// Maps fade curve position in [0,1] to value in [0,1]
+	typedef double (*Func) (double pos);
+
+	inline double LinearFunc(double pos)
+		{ return pos; }
+	inline double PowFunc(double pos)
+		{ return pos * pos; }
+	inline double SqrtFunc(double pos)
+		{ return std::sqrt(pos); }
+	inline double LogFunc(double pos)
+		{ return std::log10(1.0 + pos * 99.0) * 0.5; }
+	inline double QuarterSineFunc(double pos)
+		{ return std::sin((0.5 * mpt::numbers::pi) * pos); }
+	inline double HalfSineFunc(double pos)
+		{ return (1.0 + std::cos(mpt::numbers::pi + mpt::numbers::pi * pos)) * 0.5; }
+
+	inline Func GetFadeFunc(Law fadeLaw)
+	{
+		switch(fadeLaw)
+		{
+		default:
+		case Fade::kLinear:      return LinearFunc;
+		case Fade::kPow:         return PowFunc;
+		case Fade::kSqrt:        return SqrtFunc;
+		case Fade::kLog:         return LogFunc;
+		case Fade::kQuarterSine: return QuarterSineFunc;
+		case Fade::kHalfSine:    return HalfSineFunc;
+		}
+	}
+}
+
+OPENMPT_NAMESPACE_END