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game/shared/apparent_velocity_helper.h

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+//========= Copyright Valve Corporation, All rights reserved. ============//
+//
+// Purpose: 
+//
+//=============================================================================//
+
+#ifndef APPARENT_VELOCITY_HELPER_H
+#define APPARENT_VELOCITY_HELPER_H
+#ifdef _WIN32
+#pragma once
+#endif
+
+
+inline float CalcDistance( float x, float y )
+{
+	return x - y;
+}
+
+inline float CalcDistance( const Vector &a, const Vector &b )
+{
+	return a.DistTo( b );
+}
+
+
+template<class T>
+class CDefaultCalcDistance
+{
+public:
+	static inline float CalcDistance( const T &a, const T &b )
+	{
+		return ::CalcDistance( a, b );
+	}
+};
+
+class CCalcDistance2D
+{
+public:
+	static inline float CalcDistance( const Vector &a, const Vector &b )
+	{
+		return (a-b).Length2D();
+	}
+};
+
+
+template< class T, class Functor=CDefaultCalcDistance<T> >
+class CApparentVelocity
+{
+public:
+	CApparentVelocity(const T& t0)
+	{
+		m_LastTime = -1;
+		m_LastValue = t0;
+	}
+
+	float AddSample( float time, T value )
+	{
+		float flRet = 0;
+		if ( m_LastTime != -1 )
+		{
+			flRet = Functor::CalcDistance(value, m_LastValue) / (time - m_LastTime);
+		}
+
+		m_LastTime = time;
+		m_LastValue = value;
+
+		return flRet;
+	}
+
+private:
+	T m_LastValue;
+	float m_LastTime;
+};
+
+
+#endif // APPARENT_VELOCITY_HELPER_H