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game/shared/shot_manipulator.h

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+//========= Copyright Valve Corporation, All rights reserved. ============//
+//
+// Purpose: 
+//
+//=============================================================================//
+
+#ifndef SHOT_MANIPULATOR_H
+#define SHOT_MANIPULATOR_H
+#ifdef _WIN32
+#pragma once
+#endif
+
+
+#include "mathlib/vector.h"
+
+
+extern ConVar ai_shot_bias_min;
+extern ConVar ai_shot_bias_max;
+
+
+//---------------------------------------------------------
+// Caches off a shot direction and allows you to perform
+// various operations on it without having to recalculate
+// vecRight and vecUp each time. 
+//---------------------------------------------------------
+class CShotManipulator
+{
+public:
+	CShotManipulator( const Vector &vecForward )
+	{
+		SetShootDir( vecForward );
+	};
+
+	void SetShootDir( const Vector &vecForward )
+	{
+		m_vecShotDirection = vecForward;
+		VectorVectors( m_vecShotDirection, m_vecRight, m_vecUp );
+	}
+
+	const Vector &ApplySpread( const Vector &vecSpread, float bias = 1.0 );
+
+	const Vector &GetShotDirection()	{ return m_vecShotDirection; }
+	const Vector &GetResult()			{ return m_vecResult; }
+	const Vector &GetRightVector()		{ return m_vecRight; }
+	const Vector &GetUpVector()			{ return m_vecUp;}
+
+private:
+	Vector m_vecShotDirection;
+	Vector m_vecRight;
+	Vector m_vecUp;
+	Vector m_vecResult;
+};
+
+//---------------------------------------------------------
+// Take a vector (direction) and another vector (spread) 
+// and modify the direction to point somewhere within the 
+// spread. This used to live inside FireBullets.
+//---------------------------------------------------------
+inline const Vector &CShotManipulator::ApplySpread( const Vector &vecSpread, float bias )
+{
+	// get circular gaussian spread
+	float x, y, z;
+
+	if ( bias > 1.0 )
+		bias = 1.0;
+	else if ( bias < 0.0 )
+		bias = 0.0;
+
+	float shotBiasMin = ai_shot_bias_min.GetFloat();
+	float shotBiasMax = ai_shot_bias_max.GetFloat();
+
+	// 1.0 gaussian, 0.0 is flat, -1.0 is inverse gaussian
+	float shotBias = ( ( shotBiasMax - shotBiasMin ) * bias ) + shotBiasMin;
+
+	float flatness = ( fabsf(shotBias) * 0.5 );
+
+	do
+	{
+		x = random->RandomFloat(-1,1) * flatness + random->RandomFloat(-1,1) * (1 - flatness);
+		y = random->RandomFloat(-1,1) * flatness + random->RandomFloat(-1,1) * (1 - flatness);
+		if ( shotBias < 0 )
+		{
+			x = ( x >= 0 ) ? 1.0 - x : -1.0 - x;
+			y = ( y >= 0 ) ? 1.0 - y : -1.0 - y;
+		}
+		z = x*x+y*y;
+	} while (z > 1);
+
+	m_vecResult = m_vecShotDirection + x * vecSpread.x * m_vecRight + y * vecSpread.y * m_vecUp;
+
+	return m_vecResult;
+}
+
+
+#endif // SHOT_MANIPULATOR_H