This simple library tries to find centerlines, aka the median-axis, of closed 2D geometries.

It is focused on letter like shapes, i.e. vertex loops with potential enclosed islands of loops. Loops directly connected to other loops does not work at the moment.

It uses a segmented voronoi diagram as a base, then it filters out the 'spiky' bits (green) by comparing the angle between the edge (green), and the input geometry (red) that created it. If the angle is close to 90°, it will be ignored. Note that the result (blue) technically is not a true centerline after the spikes has been filtered out, but it makes for much cleaner tool-paths etc. It also performs a line simplification on the resulting center-line.

```rust let segments = ...same as boost voronoi segments... let mut centerline = Centerline::::withsegments(segments); centerline.buildvoronoi()?; // the cosine value of the angle limit. let cosangle:f32 = 0.38; // the RDP simplification distance let centerlinesimplification:f32 = 0.1;

let = centerline.calculatecenterline(cosangle, centerlinesimplification, None)?; println!( "Result: lines:{}, linestrings:{}", centerline.lines.asref().mapor(0,|x|x.len()), centerline.linestrings.asref().mapor(0,|x|x.len()) ); ```

Gui example

sh cargo run --example fltk_gui --features=obj-rs --release The example only displays 2D, but the generated center-line is actually 3D line segments.\ The Z coordinate is the distance between the 2D center-line, and the geometry that created it.

The example GUI takes .obj files as input. The .obj file needs to be 2D in some axis aligned plane (one of the coordinates needs to be zero). Also make sure there are no intersecting outer edges.

Rust requirement

The crate is only tested on 1.56 and above (2021 edition).

Will automatically use #![feature(hash_drain_filter)] and #![feature(map_first_last)] if run on rust +nightly.

Todo

• [ ] Sometimes a shape registers as 'outside' it's convex hull
• [ ] Add opengl to fltk_gui so that the 3D aspect of the center-line can be visualized.