The function is drawn in the plane from x=? to x=?. Points are generatet randomly around the x where you point with the mouse. Each time you move the mouse ? x values are generatet randomly ±0.5 around the mouse x-coordinate.
For definition of Kα(x) see here.
The chance to "see" a col-line is very low for low α - on the other hand the chance to see a row-line is ver low for high α. Use 10° < α < 80°.