+ x /= mag;
+ y /= mag;
+ z /= mag;
+
+
+ /*
+ * Arbitrary axis rotation matrix.
+ *
+ * This is composed of 5 matrices, Rz, Ry, T, Ry', Rz', multiplied
+ * like so: Rz * Ry * T * Ry' * Rz'. T is the final rotation
+ * (which is about the X-axis), and the two composite transforms
+ * Ry' * Rz' and Rz * Ry are (respectively) the rotations necessary
+ * from the arbitrary axis to the X-axis then back. They are
+ * all elementary rotations.
+ *
+ * Rz' is a rotation about the Z-axis, to bring the axis vector
+ * into the x-z plane. Then Ry' is applied, rotating about the
+ * Y-axis to bring the axis vector parallel with the X-axis. The
+ * rotation about the X-axis is then performed. Ry and Rz are
+ * simply the respective inverse transforms to bring the arbitrary
+ * axis back to its original orientation. The first transforms
+ * Rz' and Ry' are considered inverses, since the data from the
+ * arbitrary axis gives you info on how to get to it, not how
+ * to get away from it, and an inverse must be applied.
+ *
+ * The basic calculation used is to recognize that the arbitrary
+ * axis vector (x, y, z), since it is of unit length, actually
+ * represents the sines and cosines of the angles to rotate the
+ * X-axis to the same orientation, with theta being the angle about
+ * Z and phi the angle about Y (in the order described above)
+ * as follows:
+ *
+ * cos ( theta ) = x / sqrt ( 1 - z^2 )
+ * sin ( theta ) = y / sqrt ( 1 - z^2 )
+ *
+ * cos ( phi ) = sqrt ( 1 - z^2 )
+ * sin ( phi ) = z
+ *
+ * Note that cos ( phi ) can further be inserted to the above
+ * formulas:
+ *
+ * cos ( theta ) = x / cos ( phi )
+ * sin ( theta ) = y / sin ( phi )
+ *
+ * ...etc. Because of those relations and the standard trigonometric
+ * relations, it is pssible to reduce the transforms down to what
+ * is used below. It may be that any primary axis chosen will give the
+ * same results (modulo a sign convention) using thie method.
+ *
+ * Particularly nice is to notice that all divisions that might
+ * have caused trouble when parallel to certain planes or
+ * axis go away with care paid to reducing the expressions.
+ * After checking, it does perform correctly under all cases, since
+ * in all the cases of division where the denominator would have
+ * been zero, the numerator would have been zero as well, giving
+ * the expected result.
+ */
+
+ xx = x * x;
+ yy = y * y;
+ zz = z * z;
+ xy = x * y;
+ yz = y * z;
+ zx = z * x;
+ xs = x * s;
+ ys = y * s;
+ zs = z * s;
+ one_c = 1.0F - c;
+
+ /* We already hold the identity-matrix so we can skip some statements */
+ M(0,0) = (one_c * xx) + c;
+ M(0,1) = (one_c * xy) - zs;
+ M(0,2) = (one_c * zx) + ys;
+/* M(0,3) = 0.0F; */
+
+ M(1,0) = (one_c * xy) + zs;
+ M(1,1) = (one_c * yy) + c;
+ M(1,2) = (one_c * yz) - xs;
+/* M(1,3) = 0.0F; */
+
+ M(2,0) = (one_c * zx) - ys;
+ M(2,1) = (one_c * yz) + xs;
+ M(2,2) = (one_c * zz) + c;
+/* M(2,3) = 0.0F; */
+
+/*
+ M(3,0) = 0.0F;
+ M(3,1) = 0.0F;
+ M(3,2) = 0.0F;
+ M(3,3) = 1.0F;
+*/
+ }