//#pragma once

#ifndef GTARCBALL_H_
#define GTARCBALL_H_

/*//////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2000 Microsoft Corporation. All Rights Reserved.
//
// Description:
//    This include file contains a simple version of Shoemake's arcball code
// from GGems IV.
//////////////////////////////////////////////////////////////////////////////*/

//#include <d3dxmath.h>
#include <d3dx8.h>

class GTArcBall {
public:
	GTArcBall();
	GTArcBall(int x, int y);
	GTArcBall(D3DXVECTOR3 center);
	void Reset(); // m_qNow set to identity
	void SetWindow(int w, int h, float r=0.9); // ball info - sets center
	void BeginDrag(int x, int y); // start dragging
	void Mouse(int x, int y); // right from windows...
	void EndDrag();   // button up
	void GetMatrix(D3DXMATRIX *pmat); // gets current rotation matrix
	void GetQuaternion(D3DXQUATERNION *pq)	{ *pq = m_qNow; }
	void SetQuaternion(D3DXQUATERNION *pq) { m_qNow = *pq; if (m_bDrag) m_qDown = m_qNow; }
	void Update();
protected:
	D3DXVECTOR3 ScreenToVector(int x, int y); // screen point to normalized point on the sphere
	D3DXVECTOR3 m_pCenter; // center of arcball - on screen
	D3DXVECTOR3 m_vDown; // button down quaternion
	D3DXVECTOR3 m_vCur;  // current quaternion
	D3DXQUATERNION m_qDown; // quaternion before button down
	D3DXQUATERNION m_qNow;  // composite quaternion for current drag
	int m_iWidth,m_iHeight; // window dimensions
	float m_fRadius;       // ball radius - in screen space
	bool m_bDrag;          // true if during drag
};

// add helper function - probably should be in quaternion class

// Axis to axis quaternion double angle (no normalization)
// Takes two points on unit sphere an angle THETA apart, returns
// quaternion that represents a rotation around cross product by 2*THETA.
inline D3DXQUATERNION* WINAPI D3DXQuaternionUnitAxisToUnitAxis2
	( D3DXQUATERNION *pOut, const D3DXVECTOR3 *pvFrom, const D3DXVECTOR3 *pvTo)
{
	D3DXVECTOR3 vAxis;
	D3DXVec3Cross(&vAxis, pvFrom, pvTo);	// proportional to sin(theta)
	pOut->x = vAxis.x;
	pOut->y = vAxis.y;
	pOut->z = vAxis.z;
	pOut->w = D3DXVec3Dot( pvFrom, pvTo );
	return pOut;
}

// Axis to axis quaternion 
// Takes two points on unit sphere an angle THETA apart, returns
// quaternion that represents a rotation around cross product by theta.
inline D3DXQUATERNION* WINAPI D3DXQuaternionAxisToAxis
	( D3DXQUATERNION *pOut, const D3DXVECTOR3 *pvFrom, const D3DXVECTOR3 *pvTo)
{
	D3DXVECTOR3 vA, vB;
	D3DXVec3Normalize(&vA, pvFrom);
	D3DXVec3Normalize(&vB, pvTo);
	
	D3DXVECTOR3 vHalf(vA + vB);
	D3DXVec3Normalize(&vHalf, &vHalf);

	return D3DXQuaternionUnitAxisToUnitAxis2(pOut, &vA, &vHalf);
}

#endif