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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 Mller, 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
