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matrix4.h: Extract & expose determinant

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Lars Mueller 2025-05-09 17:42:12 +02:00
parent 1f9a3b5875
commit a87ce1bad7
1 changed files with 16 additions and 6 deletions
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22
irr/include/matrix4.h
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@ -276,6 +276,8 @@ public:
/** \param out: where result matrix is written to. */
bool getInversePrimitive(CMatrix4<T> &out) const;
T determinant() const;
//! Gets the inverse matrix of this one
/** \param out: where result matrix is written to.
\return Returns false if there is no inverse matrix. */
@ -1067,6 +1069,19 @@ inline void CMatrix4<T>::translateVect(vector3df &vect) const
vect.Z = vect.Z + M[14];
}
template <class T>
inline T CMatrix4<T>::determinant() const
{
// Calculates the determinant using the rule of Sarrus.
const CMatrix4<T> &m = *this;
return (m[0] * m[5] - m[1] * m[4]) * (m[10] * m[15] - m[11] * m[14]) -
(m[0] * m[6] - m[2] * m[4]) * (m[9] * m[15] - m[11] * m[13]) +
(m[0] * m[7] - m[3] * m[4]) * (m[9] * m[14] - m[10] * m[13]) +
(m[1] * m[6] - m[2] * m[5]) * (m[8] * m[15] - m[11] * m[12]) -
(m[1] * m[7] - m[3] * m[5]) * (m[8] * m[14] - m[10] * m[12]) +
(m[2] * m[7] - m[3] * m[6]) * (m[8] * m[13] - m[9] * m[12]);
}
template <class T>
inline bool CMatrix4<T>::getInverse(CMatrix4<T> &out) const
{
@ -1076,12 +1091,7 @@ inline bool CMatrix4<T>::getInverse(CMatrix4<T> &out) const
const CMatrix4<T> &m = *this;
f32 d = (m[0] * m[5] - m[1] * m[4]) * (m[10] * m[15] - m[11] * m[14]) -
(m[0] * m[6] - m[2] * m[4]) * (m[9] * m[15] - m[11] * m[13]) +
(m[0] * m[7] - m[3] * m[4]) * (m[9] * m[14] - m[10] * m[13]) +
(m[1] * m[6] - m[2] * m[5]) * (m[8] * m[15] - m[11] * m[12]) -
(m[1] * m[7] - m[3] * m[5]) * (m[8] * m[14] - m[10] * m[12]) +
(m[2] * m[7] - m[3] * m[6]) * (m[8] * m[13] - m[9] * m[12]);
f32 d = determinant();
if (iszero(d, FLT_MIN))
return false;