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REVIEWED: MatrixDeterminant() #4780

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2025-02-23 23:04:52 +01:00
parent 85a87baf69
commit a5907bfdca
1 changed files with 17 additions and 1 deletions
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18
src/raymath.h
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@@ -1468,19 +1468,35 @@ RMAPI int Vector4Equals(Vector4 p, Vector4 q)
RMAPI float MatrixDeterminant(Matrix mat) RMAPI float MatrixDeterminant(Matrix mat)
{ {
float result = 0.0f; float result = 0.0f;
/*
// Cache the matrix values (speed optimization) // Cache the matrix values (speed optimization)
float a00 = mat.m0, a01 = mat.m1, a02 = mat.m2, a03 = mat.m3; float a00 = mat.m0, a01 = mat.m1, a02 = mat.m2, a03 = mat.m3;
float a10 = mat.m4, a11 = mat.m5, a12 = mat.m6, a13 = mat.m7; float a10 = mat.m4, a11 = mat.m5, a12 = mat.m6, a13 = mat.m7;
float a20 = mat.m8, a21 = mat.m9, a22 = mat.m10, a23 = mat.m11; float a20 = mat.m8, a21 = mat.m9, a22 = mat.m10, a23 = mat.m11;
float a30 = mat.m12, a31 = mat.m13, a32 = mat.m14, a33 = mat.m15; float a30 = mat.m12, a31 = mat.m13, a32 = mat.m14, a33 = mat.m15;
// NOTE: It takes 72 multiplication to calculate 4x4 matrix determinant
result = a30*a21*a12*a03 - a20*a31*a12*a03 - a30*a11*a22*a03 + a10*a31*a22*a03 + result = a30*a21*a12*a03 - a20*a31*a12*a03 - a30*a11*a22*a03 + a10*a31*a22*a03 +
a20*a11*a32*a03 - a10*a21*a32*a03 - a30*a21*a02*a13 + a20*a31*a02*a13 + a20*a11*a32*a03 - a10*a21*a32*a03 - a30*a21*a02*a13 + a20*a31*a02*a13 +
a30*a01*a22*a13 - a00*a31*a22*a13 - a20*a01*a32*a13 + a00*a21*a32*a13 + a30*a01*a22*a13 - a00*a31*a22*a13 - a20*a01*a32*a13 + a00*a21*a32*a13 +
a30*a11*a02*a23 - a10*a31*a02*a23 - a30*a01*a12*a23 + a00*a31*a12*a23 + a30*a11*a02*a23 - a10*a31*a02*a23 - a30*a01*a12*a23 + a00*a31*a12*a23 +
a10*a01*a32*a23 - a00*a11*a32*a23 - a20*a11*a02*a33 + a10*a21*a02*a33 + a10*a01*a32*a23 - a00*a11*a32*a23 - a20*a11*a02*a33 + a10*a21*a02*a33 +
a20*a01*a12*a33 - a00*a21*a12*a33 - a10*a01*a22*a33 + a00*a11*a22*a33; a20*a01*a12*a33 - a00*a21*a12*a33 - a10*a01*a22*a33 + a00*a11*a22*a33;
*/
// Using Laplace expansion (https://en.wikipedia.org/wiki/Laplace_expansion),
// previous operation can be simplified to 40 multiplications, decreasing matrix
// size from 4x4 to 2x2 using minors
// Cache the matrix values (speed optimization)
float m0 = mat.m0, m1 = mat.m1, m2 = mat.m2, m3 = mat.m3;
float m4 = mat.m4, m5 = mat.m5, m6 = mat.m6, m7 = mat.m7;
float m8 = mat.m8, m9 = mat.m9, m10 = mat.m10, m11 = mat.m11;
float m12 = mat.m12, m13 = mat.m13, m14 = mat.m14, m15 = mat.m15;
result = (m0*((m5*(m10*m15 - m11*m14) - m9*(m6*m15 - m7*m14) + m13*(m6*m11 - m7*m10))) -
m4*((m1*(m10*m15 - m11*m14) - m9*(m2*m15 - m3*m14) + m13*(m2*m11 - m3*m10))) +
m8*((m1*(m6*m15 - m7*m14) - m5*(m2*m15 - m3*m14) + m13*(m2*m7 - m3*m6))) -
m12*((m1*(m6*m11 - m7*m10) - m5*(m2*m11 - m3*m10) + m9*(m2*m7 - m3*m6))))
return result; return result;
} }