inverting a 4x4 matrix

Question

hello, i am looking for a sample code implementation on how to invert a 4x4 matrix. i know there is gaussian eleminiation, LU decomposition, etc. but instead of looking at them in detail i am really just looking for the code to do this.

language ideally C++, data is available in array of 16 floats in cloumn-major order.

thank you!

Answer 1

FOR 3x3 MATRIX

CHANGE THE CODE ACCORDING TO YOUR REQUIREMENT

http://www.dreamincode.net/code/snippet1156.htm

Answer 2

There appears to be a VB version at this place.

Answer 3

You can use the GNU Scientific Library or look the code up in it.

Edit: You seem to want the Linear Algebra section.

Answer 4

Here is a small (just one header) C++ vector math library (geared towards 3D programming). If you use it, keep in mind that layout of its matrices in memory is inverted comparing to what OpenGL expects, I had fun time figuring it out...

Answer 5

here:

bool gluInvertMatrix(const double m[16], double invOut[16])
{
double inv[16], det;
int i;

inv[0] =   m[5]*m[10]*m[15] - m[5]*m[11]*m[14] - m[9]*m[6]*m[15]
+ m[9]*m[7]*m[14] + m[13]*m[6]*m[11] - m[13]*m[7]*m[10];
inv[4] =  -m[4]*m[10]*m[15] + m[4]*m[11]*m[14] + m[8]*m[6]*m[15]
- m[8]*m[7]*m[14] - m[12]*m[6]*m[11] + m[12]*m[7]*m[10];
inv[8] =   m[4]*m[9]*m[15] - m[4]*m[11]*m[13] - m[8]*m[5]*m[15]
+ m[8]*m[7]*m[13] + m[12]*m[5]*m[11] - m[12]*m[7]*m[9];
inv[12] = -m[4]*m[9]*m[14] + m[4]*m[10]*m[13] + m[8]*m[5]*m[14]
- m[8]*m[6]*m[13] - m[12]*m[5]*m[10] + m[12]*m[6]*m[9];
inv[1] =  -m[1]*m[10]*m[15] + m[1]*m[11]*m[14] + m[9]*m[2]*m[15]
- m[9]*m[3]*m[14] - m[13]*m[2]*m[11] + m[13]*m[3]*m[10];
inv[5] =   m[0]*m[10]*m[15] - m[0]*m[11]*m[14] - m[8]*m[2]*m[15]
+ m[8]*m[3]*m[14] + m[12]*m[2]*m[11] - m[12]*m[3]*m[10];
inv[9] =  -m[0]*m[9]*m[15] + m[0]*m[11]*m[13] + m[8]*m[1]*m[15]
- m[8]*m[3]*m[13] - m[12]*m[1]*m[11] + m[12]*m[3]*m[9];
inv[13] =  m[0]*m[9]*m[14] - m[0]*m[10]*m[13] - m[8]*m[1]*m[14]
+ m[8]*m[2]*m[13] + m[12]*m[1]*m[10] - m[12]*m[2]*m[9];
inv[2] =   m[1]*m[6]*m[15] - m[1]*m[7]*m[14] - m[5]*m[2]*m[15]
+ m[5]*m[3]*m[14] + m[13]*m[2]*m[7] - m[13]*m[3]*m[6];
inv[6] =  -m[0]*m[6]*m[15] + m[0]*m[7]*m[14] + m[4]*m[2]*m[15]
- m[4]*m[3]*m[14] - m[12]*m[2]*m[7] + m[12]*m[3]*m[6];
inv[10] =  m[0]*m[5]*m[15] - m[0]*m[7]*m[13] - m[4]*m[1]*m[15]
+ m[4]*m[3]*m[13] + m[12]*m[1]*m[7] - m[12]*m[3]*m[5];
inv[14] = -m[0]*m[5]*m[14] + m[0]*m[6]*m[13] + m[4]*m[1]*m[14]
- m[4]*m[2]*m[13] - m[12]*m[1]*m[6] + m[12]*m[2]*m[5];
inv[3] =  -m[1]*m[6]*m[11] + m[1]*m[7]*m[10] + m[5]*m[2]*m[11]
- m[5]*m[3]*m[10] - m[9]*m[2]*m[7] + m[9]*m[3]*m[6];
inv[7] =   m[0]*m[6]*m[11] - m[0]*m[7]*m[10] - m[4]*m[2]*m[11]
+ m[4]*m[3]*m[10] + m[8]*m[2]*m[7] - m[8]*m[3]*m[6];
inv[11] = -m[0]*m[5]*m[11] + m[0]*m[7]*m[9] + m[4]*m[1]*m[11]
- m[4]*m[3]*m[9] - m[8]*m[1]*m[7] + m[8]*m[3]*m[5];
inv[15] =  m[0]*m[5]*m[10] - m[0]*m[6]*m[9] - m[4]*m[1]*m[10]
+ m[4]*m[2]*m[9] + m[8]*m[1]*m[6] - m[8]*m[2]*m[5];

det = m[0]*inv[0] + m[1]*inv[4] + m[2]*inv[8] + m[3]*inv[12];
if (det == 0)
 return false;

det = 1.0 / det;

for (i = 0; i < 16; i++)
 invOut[i] = inv[i] * det;

return true;
}

This was lifted from MESA implementation of the GLU library.

Answer 6

If you're looking for 'just works' implementation that is also very optimized without the need to understand the code, I highly reccommend using Intel's optimized SSE matrix inverse routine described here. There's also a reference impelementation for both gaussian elimination and Cramer's rule in C.

I warn though, the SSE code is not pretty if you don't understand MMX/SSE intrinsics.

Answer 7

If you need a C++ matrix library with a lot of functions, have a look at Eigen library - http://eigen.tuxfamily.org