There are different ways to create concave hulls in QGIS (= alpha shapes, look at Introduction to Alpha Shapes (pdf), K. Fischer 2000 and On the creation of concave hulls and the various ways of doing that.(alpha-shapes)On the creation of concave hulls and the various ways of doing that.(alpha-shapes), in French, which I take the figures).
- Concave Hull script in the processing toolbox, you can create holes
- The new Concave Hull plugin with clusters (if you want)
- The PgRouting Layer plugin of Anita Graser (underdark), based on PostGIS (A Closer Look at Alpha Shapes in pgRouting)
You can also use
- GRASS GIS (Create concave hull)
- OpenJUMP (Concave hull based on JTS extension)
- Python only (The fading shape of alpha , Drawing Boundaries In Python or Alpha shapes in Python, using the hull C program), examples in my scripts (in French), concave_hull1.py and concave_hull2.py
- R spatial with the alphahull package (there is also alphashape3D, for 3D "concave hulls"): look at my script (in French) alpha_shape.Ralpha_shape.R
With alphashape3D
PostGIS (PostGIS Concave Hull)
SpatiaLite ( Delaunay Triangulation, Convex Hull and Concave Hull)