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/** @file aiMatrix3x3.h
 *  @brief Definition of a 3x3 matrix, including operators when compiling in C++
 */
#ifndef AI_MATRIX3x3_H_INC
#define AI_MATRIX3x3_H_INC

#ifdef __cplusplus
extern "C" {
#endif

struct aiMatrix4x4;
struct aiVector2D;

// ---------------------------------------------------------------------------
/** @brief Represents a row-major 3x3 matrix
 *
 *  There's much confusion about matrix layouts (colum vs. row order). 
 *  This is *always* a row-major matrix. Even with the
 *  aiProcess_ConvertToLeftHanded flag.
 */
struct aiMatrix3x3
{
#ifdef __cplusplus

	aiMatrix3x3 () :	
		a1(1.0f), a2(0.0f), a3(0.0f), 
		b1(0.0f), b2(1.0f), b3(0.0f), 
		c1(0.0f), c2(0.0f), c3(1.0f) {}

	aiMatrix3x3 (	float _a1, float _a2, float _a3,
					float _b1, float _b2, float _b3,
					float _c1, float _c2, float _c3) :	
		a1(_a1), a2(_a2), a3(_a3), 
		b1(_b1), b2(_b2), b3(_b3), 
		c1(_c1), c2(_c2), c3(_c3)
	{}

public:

	// matrix multiplication. beware, not commutative
	aiMatrix3x3& operator *= (const aiMatrix3x3& m);
	aiMatrix3x3  operator  * (const aiMatrix3x3& m) const;

	// array access operators
	float* operator[]       (unsigned int p_iIndex);
	const float* operator[] (unsigned int p_iIndex) const;

	// comparison operators
	bool operator== (const aiMatrix4x4 m) const;
	bool operator!= (const aiMatrix4x4 m) const;

public:

	// -------------------------------------------------------------------
	/** @brief Construction from a 4x4 matrix. The remaining parts 
	 *  of the matrix are ignored.
	 */
	explicit aiMatrix3x3( const aiMatrix4x4& pMatrix);

	// -------------------------------------------------------------------
	/** @brief Transpose the matrix
	 */
	aiMatrix3x3& Transpose();

	// -------------------------------------------------------------------
	/** @brief Invert the matrix.
	 *  If the matrix is not invertible all elements are set to qnan.
	 *  Beware, use (f != f) to check whether a float f is qnan.
	 */
	aiMatrix3x3& Inverse();
	float Determinant() const;

public:
	// -------------------------------------------------------------------
	/** @brief Returns a rotation matrix for a rotation around z
	 *  @param a Rotation angle, in radians
	 *  @param out Receives the output matrix
	 *  @return Reference to the output matrix
	 */
	static aiMatrix3x3& RotationZ(float a, aiMatrix3x3& out);

	// -------------------------------------------------------------------
	/** @brief Returns a rotation matrix for a rotation around
	 *    an arbitrary axis.
	 *
	 *  @param a Rotation angle, in radians
	 *  @param axis Axis to rotate around
	 *  @param out To be filled
	 */
	static aiMatrix3x3& Rotation( float a, 
		const aiVector3D& axis, aiMatrix3x3& out);

	// -------------------------------------------------------------------
	/** @brief Returns a translation matrix 
	 *  @param v Translation vector
	 *  @param out Receives the output matrix
	 *  @return Reference to the output matrix
	 */
	static aiMatrix3x3& Translation( const aiVector2D& v, aiMatrix3x3& out);

	// -------------------------------------------------------------------
	/** @brief A function for creating a rotation matrix that rotates a
	 *  vector called "from" into another vector called "to".
	 * Input : from[3], to[3] which both must be *normalized* non-zero vectors
	 * Output: mtx[3][3] -- a 3x3 matrix in colum-major form
	 * Authors: Tomas Möller, John Hughes
	 *          "Efficiently Building a Matrix to Rotate One Vector to Another"
	 *          Journal of Graphics Tools, 4(4):1-4, 1999
	 */
	static aiMatrix3x3& FromToMatrix(const aiVector3D& from, 
		const aiVector3D& to, aiMatrix3x3& out);

#endif // __cplusplus


	float a1, a2, a3;
	float b1, b2, b3;
	float c1, c2, c3;
};

#ifdef __cplusplus
} // end of extern C
#endif

#endif // AI_MATRIX3x3_H_INC
