In the model panel you can choose a discrete surface, on which the discrete geodesics shall be shown. Pick a starting point for the geodesic by holding "i" pressed and clicking at any point of the surface.

Curve panel controls:

Slider "Length"	Analytic length of geodesic curve.
Slider "Direction"	Starting Direction of geodesic curve. The direction is given by an angle in the tangent space at the selected point.
Slider "Element Index"	Index of the element, which contains the starting point of the geodesic curve.