NURBS_Property GLU_PARAMETRIC_ERROR

Hello !

I have a problem regarding the gluNurbsProperty GLU_PARAMETRIC_ERROR. It is supposed to render a B-Spline curve or a B-Spline surface with a maximum distance between real and approximated object given by GLU_PARAMETRIC_TOLERANCE. The default value of this is 0.5 Pixels.
I can adjust this value anyway I want, but I do not get any change in the scene. Is this Property correctly implemented in GLU_VERSION_1_2 or am I doing something wrong (though checking the 10th time by now)?
Anybody encountered this too and got it right?

I used it, and it only changes your nurb if is < 0.5, if u use 0.0001 your nurbs will be hiper tessellated… XD
Lorien