IceMatrix4x4.cpp

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// Precompiled Header
#include "Stdafx.h"

using namespace IceMaths;


ICEMATHS_API void IceMaths::InvertPRMatrix(Matrix4x4& dest, const Matrix4x4& src)
{
        dest.m[0][0] = src.m[0][0];
        dest.m[1][0] = src.m[0][1];
        dest.m[2][0] = src.m[0][2];
        dest.m[3][0] = -(src.m[3][0]*src.m[0][0] + src.m[3][1]*src.m[0][1] + src.m[3][2]*src.m[0][2]);

        dest.m[0][1] = src.m[1][0];
        dest.m[1][1] = src.m[1][1];
        dest.m[2][1] = src.m[1][2];
        dest.m[3][1] = -(src.m[3][0]*src.m[1][0] + src.m[3][1]*src.m[1][1] + src.m[3][2]*src.m[1][2]);

        dest.m[0][2] = src.m[2][0];
        dest.m[1][2] = src.m[2][1];
        dest.m[2][2] = src.m[2][2];
        dest.m[3][2] = -(src.m[3][0]*src.m[2][0] + src.m[3][1]*src.m[2][1] + src.m[3][2]*src.m[2][2]);

        dest.m[0][3] = 0.0f;
        dest.m[1][3] = 0.0f;
        dest.m[2][3] = 0.0f;
        dest.m[3][3] = 1.0f;
}

// Compute the cofactor of the Matrix at a specified location
float Matrix4x4::CoFactor(udword row, udword col) const
{
        return   (( m[(row+1)&3][(col+1)&3]*m[(row+2)&3][(col+2)&3]*m[(row+3)&3][(col+3)&3] +
                                m[(row+1)&3][(col+2)&3]*m[(row+2)&3][(col+3)&3]*m[(row+3)&3][(col+1)&3] +
                                m[(row+1)&3][(col+3)&3]*m[(row+2)&3][(col+1)&3]*m[(row+3)&3][(col+2)&3])
                        -  (m[(row+3)&3][(col+1)&3]*m[(row+2)&3][(col+2)&3]*m[(row+1)&3][(col+3)&3] +
                                m[(row+3)&3][(col+2)&3]*m[(row+2)&3][(col+3)&3]*m[(row+1)&3][(col+1)&3] +
                                m[(row+3)&3][(col+3)&3]*m[(row+2)&3][(col+1)&3]*m[(row+1)&3][(col+2)&3])) * ((row + col) & 1 ? -1.0f : +1.0f);
}

// Compute the determinant of the Matrix
float Matrix4x4::Determinant() const
{
        return  m[0][0] * CoFactor(0, 0) +
                        m[0][1] * CoFactor(0, 1) +
                        m[0][2] * CoFactor(0, 2) +
                        m[0][3] * CoFactor(0, 3);
}

// Compute the inverse of the matrix
Matrix4x4& Matrix4x4::Invert()
{
        float Det = Determinant();
        Matrix4x4 Temp;

        if(fabsf(Det) < MATRIX4X4_EPSILON)
                return  *this;          // The matrix is not invertible! Singular case!

        float IDet = 1.0f / Det;

        Temp.m[0][0] = CoFactor(0,0) * IDet;
        Temp.m[1][0] = CoFactor(0,1) * IDet;
        Temp.m[2][0] = CoFactor(0,2) * IDet;
        Temp.m[3][0] = CoFactor(0,3) * IDet;
        Temp.m[0][1] = CoFactor(1,0) * IDet;
        Temp.m[1][1] = CoFactor(1,1) * IDet;
        Temp.m[2][1] = CoFactor(1,2) * IDet;
        Temp.m[3][1] = CoFactor(1,3) * IDet;
        Temp.m[0][2] = CoFactor(2,0) * IDet;
        Temp.m[1][2] = CoFactor(2,1) * IDet;
        Temp.m[2][2] = CoFactor(2,2) * IDet;
        Temp.m[3][2] = CoFactor(2,3) * IDet;
        Temp.m[0][3] = CoFactor(3,0) * IDet;
        Temp.m[1][3] = CoFactor(3,1) * IDet;
        Temp.m[2][3] = CoFactor(3,2) * IDet;
        Temp.m[3][3] = CoFactor(3,3) * IDet;

        *this = Temp;

        return  *this;
}