This is a new implementation of the bn_mat_inverse() and bn_mat_determinant routines in src/libbn/mat.c of BRL-CAD; with the following amendments:

bn_mat_inverse:

* The matrix pointed at by "input" is inverted and stored in the area

* pointed at by "output".

*

* Invert a 4-by-4 matrix using direct computation.

* Uses 100 multiplications and 61 additions or substractions, total

bn_mat_determinant:

* Calculates the determinant of the 4X4 matrix

* (This implementation requires only 34 multiplications

* and 20 additions or substractions, saving 6 multiplications

* and 3 additions or substractions compared to the previous one.