/**
* Creates an AffineMatrix representing a rotation about the origin by some angle around the given
* axis.
*
* @param theta double
* @param axis double[]
* @return AffineMatrix
*/
public static Affine3DMatrix Rotation(double theta, double[] axis) {
Affine3DMatrix at = new Affine3DMatrix(null);
double[][] atMatrix = at.matrix;
double norm = Math.sqrt(axis[0] * axis[0] + axis[1] * axis[1] + axis[2] * axis[2]);
double x = axis[0] / norm, y = axis[1] / norm, z = axis[2] / norm;
double c = Math.cos(theta), s = Math.sin(theta);
double t = 1 - c;
// matrix elements not listed are zero
atMatrix[0][0] = t * x * x + c;
atMatrix[0][1] = t * x * y - s * z;
atMatrix[0][2] = t * x * y + s * y;
atMatrix[1][0] = t * x * y + s * z;
atMatrix[1][1] = t * y * y + c;
atMatrix[1][2] = t * y * z - s * x;
atMatrix[2][0] = t * x * z - s * y;
atMatrix[2][1] = t * y * z + s * x;
atMatrix[2][2] = t * z * z + c;
atMatrix[3][3] = 1;
return at;
}
