Matrix::Matrix()
{
SetIdentity();
}
Matrix& Matrix::SetInverse(const Matrix& mStart)
{
const int size = 4;
bool bSwap = false;
Matrix m(mStart);
SetIdentity();
for (int row = 0; row < size; row++) {
//
// pick the largest row in the rowth column
//
float max = abs(m.m_m[row][row]);
int rowMax = row;
for (int rowIndex = row + 1; rowIndex < size; rowIndex++) {
if (abs(m.m_m[rowIndex][row]) > max) {
max = abs(m.m_m[rowIndex][row]);
rowMax = rowIndex;
}
}
//
// swap this row with the largest row
//
if (rowMax != row) {
//
// swap rows
//
bSwap = true;
for (int col = 0; col < size; col++) {
Swap(m.m_m[row][col], m.m_m[rowMax][col]);
Swap( m_m[row][col], m_m[rowMax][col]);
}
}
//
// scale to get a one in the diagonal
//
float scale = m.m_m[row][row];
if (scale != 1.0f) {
float rscale = 1.0f / scale;
int col;
m.m_m[row][row] = 1;
for (col = row + 1; col < size; col++) {
m.m_m[row][col] *= rscale;
}
if (bSwap) {
for (col = 0; col < size; col++) {
m_m[row][col] *= rscale;
}
} else {
m_m[row][row] = rscale;
for (col = 0; col < row; col++) {
m_m[row][col] *= rscale;
}
}
}
//
// get zeros in the rowth column of each row
// by subtracting a multiple of row from row2
//
for (int row2 = 0; row2 < size; row2++) {
if (row2 != row) {
float scale = m.m_m[row2][row];
if (scale != 0) {
int col;
m.m_m[row2][row] = 0;
for (col = row + 1; col < size; col++) {
m.m_m[row2][col] -= scale * m.m_m[row][col];
}
if (bSwap) {
for (col = 0; col < size; col++) {
m_m[row2][col] -= scale * m_m[row][col];
}
} else {
for (col = 0; col <= row; col++) {
m_m[row2][col] -= scale * m_m[row][col];
}
}
}
}
}
}
m_type = TransformUnknown;
return *this;
}
