static void invertMatrix(ref float[] output, ref float[] m)
{
double m0, m1, m2, m3, s;
double[] r0 = new double[8], r1 = new double[8], r2 = new double[8], r3 = new double[8];
r0[0] = MAT_Get(m, 0, 0); r0[1] = MAT_Get(m, 0, 1);
r0[2] = MAT_Get(m, 0, 2); r0[3] = MAT_Get(m, 0, 3);
r0[4] = 1.0; r0[5] = r0[6] = r0[7] = 0.0;
r1[0] = MAT_Get(m, 1, 0); r1[1] = MAT_Get(m, 1, 1);
r1[2] = MAT_Get(m, 1, 2); r1[3] = MAT_Get(m, 1, 3);
r1[5] = 1.0; r1[4] = r1[6] = r1[7] = 0.0;
r2[0] = MAT_Get(m, 2, 0); r2[1] = MAT_Get(m, 2, 1);
r2[2] = MAT_Get(m, 2, 2); r2[3] = MAT_Get(m, 2, 3);
r2[6] = 1.0; r2[4] = r2[5] = r2[7] = 0.0;
r3[0] = MAT_Get(m, 3, 0); r3[1] = MAT_Get(m, 3, 1);
r3[2] = MAT_Get(m, 3, 2); r3[3] = MAT_Get(m, 3, 3);
r3[7] = 1.0; r3[4] = r3[5] = r3[6] = 0.0;
/* Choose myPivot, or die. */
if (Math.Abs(r3[0]) > Math.Abs(r2[0])) SWAP_ROWS(ref r3, ref r2);
if (Math.Abs(r2[0]) > Math.Abs(r1[0])) SWAP_ROWS(ref r2, ref r1);
if (Math.Abs(r1[0]) > Math.Abs(r0[0])) SWAP_ROWS(ref r1, ref r0);
if (0.0 == r0[0])
{
Debug.Assert(false, "could not invert matrix");
}
/* Eliminate first variable. */
m1 = r1[0] / r0[0]; m2 = r2[0] / r0[0]; m3 = r3[0] / r0[0];
s = r0[1]; r1[1] -= m1 * s; r2[1] -= m2 * s; r3[1] -= m3 * s;
s = r0[2]; r1[2] -= m1 * s; r2[2] -= m2 * s; r3[2] -= m3 * s;
s = r0[3]; r1[3] -= m1 * s; r2[3] -= m2 * s; r3[3] -= m3 * s;
s = r0[4];
if (s != 0.0) { r1[4] -= m1 * s; r2[4] -= m2 * s; r3[4] -= m3 * s; }
s = r0[5];
if (s != 0.0) { r1[5] -= m1 * s; r2[5] -= m2 * s; r3[5] -= m3 * s; }
s = r0[6];
if (s != 0.0) { r1[6] -= m1 * s; r2[6] -= m2 * s; r3[6] -= m3 * s; }
s = r0[7];
if (s != 0.0) { r1[7] -= m1 * s; r2[7] -= m2 * s; r3[7] -= m3 * s; }
/* Choose myPivot, or die. */
if (Math.Abs(r3[1]) > Math.Abs(r2[1])) SWAP_ROWS(ref r3, ref r2);
if (Math.Abs(r2[1]) > Math.Abs(r1[1])) SWAP_ROWS(ref r2, ref r1);
if (0.0 == r1[1])
{
Debug.Assert(false, "could not invert matrix");
}
/* Eliminate second variable. */
m2 = r2[1] / r1[1]; m3 = r3[1] / r1[1];
r2[2] -= m2 * r1[2]; r3[2] -= m3 * r1[2];
r2[3] -= m2 * r1[3]; r3[3] -= m3 * r1[3];
s = r1[4]; if (0.0 != s) { r2[4] -= m2 * s; r3[4] -= m3 * s; }
s = r1[5]; if (0.0 != s) { r2[5] -= m2 * s; r3[5] -= m3 * s; }
s = r1[6]; if (0.0 != s) { r2[6] -= m2 * s; r3[6] -= m3 * s; }
s = r1[7]; if (0.0 != s) { r2[7] -= m2 * s; r3[7] -= m3 * s; }
/* Choose myPivot, or die. */
if (Math.Abs(r3[2]) > Math.Abs(r2[2])) SWAP_ROWS(ref r3, ref r2);
if (0.0 == r2[2])
{
Debug.Assert(false, "could not invert matrix");
}
/* Eliminate third variable. */
m3 = r3[2] / r2[2];
r3[3] -= m3 * r2[3]; r3[4] -= m3 * r2[4];
r3[5] -= m3 * r2[5]; r3[6] -= m3 * r2[6];
r3[7] -= m3 * r2[7];
/* Last check. */
if (0.0 == r3[3])
{
Debug.Assert(false, "could not invert matrix");
}
s = 1.0 / r3[3]; /* Now back substitute row 3. */
r3[4] *= s; r3[5] *= s; r3[6] *= s; r3[7] *= s;
m2 = r2[3]; /* Now back substitute row 2. */
s = 1.0 / r2[2];
r2[4] = s * (r2[4] - r3[4] * m2); r2[5] = s * (r2[5] - r3[5] * m2);
r2[6] = s * (r2[6] - r3[6] * m2); r2[7] = s * (r2[7] - r3[7] * m2);
m1 = r1[3];
r1[4] -= r3[4] * m1; r1[5] -= r3[5] * m1;
r1[6] -= r3[6] * m1; r1[7] -= r3[7] * m1;
m0 = r0[3];
r0[4] -= r3[4] * m0; r0[5] -= r3[5] * m0;
r0[6] -= r3[6] * m0; r0[7] -= r3[7] * m0;
m1 = r1[2]; /* Now back substitute row 1. */
s = 1.0 / r1[1];
r1[4] = s * (r1[4] - r2[4] * m1); r1[5] = s * (r1[5] - r2[5] * m1);
r1[6] = s * (r1[6] - r2[6] * m1); r1[7] = s * (r1[7] - r2[7] * m1);
m0 = r0[2];
r0[4] -= r2[4] * m0; r0[5] -= r2[5] * m0;
r0[6] -= r2[6] * m0; r0[7] -= r2[7] * m0;
m0 = r0[1]; /* Now back substitute row 0. */
s = 1.0 / r0[0];
r0[4] = s * (r0[4] - r1[4] * m0); r0[5] = s * (r0[5] - r1[5] * m0);
r0[6] = s * (r0[6] - r1[6] * m0); r0[7] = s * (r0[7] - r1[7] * m0);
MAT_Set(ref output, 0, 0, r0[4]); MAT_Set(ref output, 0, 1, r0[5]);
MAT_Set(ref output, 0, 2, r0[6]); MAT_Set(ref output, 0, 3, r0[7]);
MAT_Set(ref output, 1, 0, r1[4]); MAT_Set(ref output, 1, 1, r1[5]);
MAT_Set(ref output, 1, 2, r1[6]); MAT_Set(ref output, 1, 3, r1[7]);
MAT_Set(ref output, 2, 0, r2[4]); MAT_Set(ref output, 2, 1, r2[5]);
MAT_Set(ref output, 2, 2, r2[6]); MAT_Set(ref output, 2, 3, r2[7]);
MAT_Set(ref output, 3, 0, r3[4]); MAT_Set(ref output, 3, 1, r3[5]);
MAT_Set(ref output, 3, 2, r3[6]); MAT_Set(ref output, 3, 3, r3[7]);
}
