/// <summary>
/// Rotate around an axis. Angle in degrees.
/// </summary>
/// <param name="angle"></param>
/// <param name="axis"></param>
public void RotateAboutOrigin(double angle, IVector3D axis)
{
axis.Norm();
double a = angle * Math.PI / 180;
double cosA = Math.Cos(a);
double sinA = Math.Sin(a);
double xx = Math.Pow(axis.X, 2);
double yy = Math.Pow(axis.Y, 2);
double zz = Math.Pow(axis.Z, 2);
double xy = axis.X * axis.Y;
double yz = axis.Y * axis.Z;
double xz = axis.X * axis.Z;
double[][] data = new double[4][];
data[0] = new double[] { xx + (1 - xx) * cosA, xy *(1 - cosA) - axis.Z * sinA, xz *(1 - cosA) + axis.Y * sinA, 0 };
data[1] = new double[] { xy *(1 - cosA) + axis.Z * sinA, yy + (1 - yy) * cosA, yz *(1 - cosA) - axis.X * sinA, 0 };
data[2] = new double[] { xz *(1 - cosA) - axis.Y * sinA, yz *(1 - cosA) + axis.X * sinA, zz + (1 - zz) * cosA, 0 };
data[3] = new double[] { 0, 0, 0, 1 };
IMatrix m = new IMatrix(data);
TransformationMatrix = IMatrix.Mult(TransformationMatrix, m);
}
