Alpha Shape

Alpha Shape converts the selected items into Alpha shapes (concave hulls) using Edelsbrunner's algorithm

Select Analysis > Geometry > Hulls > Alpha Shape.

This opens the Alpha Shape options:

Option Description

Approximate

The tolerance value is the maximum distance allowed between the original shape and the new shape.

The smaller the tolerance, the greater the number of LineString item segments used in the shape.

Select this option and use the slider to choose an approximate tolerance.

Move the slider to change the tolerance value or type in an Exact value and click Apply.

Exact Tolerance

Select this option if you wish to enter the exact tolerance.

If the preview screen shows the desired result click Apply. The lower the value the more vertices will be created.

Styles Before

Check the Before tickbox to see and set the pre-operation condition for the Pen and Brush respectively.

After

Check the After tickbox to see and set the pre-operation condition for the Pen and Brush respectively.

Keep original

Check the Keep original Item(s) tickbox if you want to keep the original item.

Remember Alpha shapes work on a single item. If you are working on a set of points, ensure you group them together first using UNION.