A C# library to convert a complex polygon into triangles. Support includes:
- multiple polygons
- polygon holes
- fusion vertex (same vertex is used by two sub polygons)
The project was developed as part of a Unity project to visualize the intersection between a 3D mesh and a plane.
The included Windows Forms project PolygonDisplay visualizes the Polygon, the detected splits and the Monotones.
Create a PlanePolygonBuilder(plane) and call repeatedly AddEdge(start, end).
After adding the last edge, call Build().
The result contains a vertex array and a list of Triangles. A Triangle is defined by three consecutive indices in the vertex array.
The 3D vertices of the edge are converted to 2D by rotating them along the plane and removing the depth component.
Unity is using its own types for Vector2, Vector3, Plane and Quaternion, while the common code uses thy types from System.Numerics.
The #if UNITY_EDITOR || UNITY_STANDALONE directive changes the namespace and the different case for the property names like Vector2.x vs Vector2.X.
To use the code, copy all files from PolygonTriangulation to the unity scripts folder.
To test the intermediate steps, create a IEdgesToPolygonBuilder by calling PlanePolygonBuilder.CreatePolygonBuilder().
Call AddEdge(start, end) to add the polygon edges and finally BuildPolygon() to receive a IPlanePolygon which contains a
Polygon and the original 3D vertices.
The polygon contains the 2D vertices in the same order as the 3D vertices of the result.
Alternatively construct the Polygon with Polygon.Build().
Create a new PolygonTriangulator(polygon) and call BuildTriangles().
That uses Trapezoidation to split the Polygon into Monotones and then
triangulates those monotones.
To test only the edges to polygon conversion, create a IPolygonLineDetector by calling PlanePolygonBuilder.CreatePolygonLineDetector().
Call JoinEdgesToPolygones(pairsOfEdges) to create polygon lines. It results in lists of ClosedPolygons and UnclosedPolygons.
Unclosed polygons can be joined by TryClusteringUnclosedEnds(vertices).
That merges unclosed polygons by considering vertex coordinates with small distances as the same vertex.