Centerline

Finds 'a' centerline of closed 2D geometries. 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.

let segments = ...same as boost voronoi segments...
let mut centerline = Centerline::<i32, f32, i64, f64>::with_segments(segments);
centerline.build_voronoi()?;
let normalized_dot_product_limit:f32 = 0.38;
let centerline_simplification:f32 = 0.1;

let _= centerline.calculate_centerline(normalized_dot_product_limit, centerline_simplification)?;
println!(
   "Result: lines:{}, line_strings:{}",
   centerline.lines.as_ref().map_or(0,|x|x.len()),
   centerline.line_strings.as_ref().map_or(0,|x|x.len())
);

Gui example

cargo +nightly run --example fltk_gui

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.

It should be possible to replace the example input data by overwriting the rust.obj file in the example folder. The new .obj file just needs to be 2D in some axis aligned plane. Make sure there are no intersecting outer edges though.

Rust requirement

Requires #![feature(hash_drain_filter)] i.e. +nightly

Todo

• Group related shapes together based on convex hull and not just AABB
• Rayon over each shape group (problem: boostvoronoi diagrams uses std::cell::Cell)
• Open file dialogue for fltk_gui
• Maybe, maybe make it possible to save result from fltk_gui :)
• Make an option to remove inner center-lines of inner shapes. I.e. the holes in letters.
• Add opengl to fltk_gui so that the 3D aspect of the center-line can be visualized.