CGAL users discussion list

["Daniel Duque" <>]

>Very small values give you nothing back as then the alpha shape is
>just the input point set. There will be an alpha shape edge, if a circle of
>radius sqrt(alpha) can not pass between the two vertices, that is if
>the squared distance of the two vertices is smaller than alpha.

Correct. Sorry for my confusion, I was thinking about 3D shapes. Plus, I
always confuse the alpha-shape and its boundary. My suggestion is, then,
more relevant: are you sure your value of alpha is not very low?

Try a very high value: it should give you the convex hull. Add some
extreme points (like a large square, with coordinates (-100,-100),
(-100,100) etc) so you know the answer in advance.

Best,

Daniel