urho3d/Source/Engine/Math/Matrix3.cpp

//
// Copyright (c) 2008-2013 the Urho3D project.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// THE SOFTWARE.
//

#include "Precompiled.h"
#include "Matrix3.h"

namespace Urho3D
{

const Matrix3 Matrix3::ZERO(
    0.0f, 0.0f, 0.0f,
    0.0f, 0.0f, 0.0f,
    0.0f, 0.0f, 0.0f);

const Matrix3 Matrix3::IDENTITY(
    1.0f, 0.0f, 0.0f,
    0.0f, 1.0f, 0.0f,
    0.0f, 0.0f, 1.0f);

Matrix3 Matrix3::Inverse() const
{
    float det = m00_ * m11_ * m22_ +
        m10_ * m21_ * m02_ +
        m20_ * m01_ * m12_ -
        m20_ * m11_ * m02_ -
        m10_ * m01_ * m22_ -
        m00_ * m21_ * m12_;
    
    float invDet = 1.0f / det;
    
    return Matrix3(
        (m11_ * m22_ - m21_ * m12_) * invDet,
        -(m01_ * m22_ - m21_ * m02_) * invDet,
        (m01_ * m12_ - m11_ * m02_) * invDet,
        -(m10_ * m22_ - m20_ * m12_) * invDet,
        (m00_ * m22_ - m20_ * m02_) * invDet,
        -(m00_ * m12_ - m10_ * m02_) * invDet,
        (m10_ * m21_ - m20_ * m11_) * invDet,
        -(m00_ * m21_ - m20_ * m01_) * invDet,
        (m00_ * m11_ - m10_ * m01_) * invDet
    );
}

}