.NET 8 library for triangulating 2D/3D WKB geometries (PolyhedralSurface/MultiPolygon/Polygon/Multiline/Line) using Earcut algorithm. Lines can be triangulated using the TubeGeometry algorithm from Three.JS.
https://www.nuget.org/packages/bertt.triangulator/
var buildingWkb = File.ReadAllBytes(@"testdata/building.wkb");
var wkbTriangulated = Triangulator.Triangulate(buildingWkb);
var triangulatedGeometry = (PolyhedralSurface)Geometry.Deserialize<WkbSerializer>(wkbTriangulated);
Assert.IsTrue(triangulatedGeometry.Geometries.Count == 22);
From:
POLYHEDRALSURFACE Z (((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),((0 0 0, 0 1 0, 0 1 1, 0 0 1, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)), ((1 1 1, 1 0 1, 0 0 1, 0 1 1, 1 1 1)),((1 1 1, 1 0 1, 1 0 0, 1 1 0, 1 1 1)),((1 1 1, 1 1 0, 0 1 0, 0 1 1, 1 1 1)))
To:
POLYHEDRALSURFACE Z (((0 0 0,0 1 0,1 0 0,0 0 0)),((1 1 0,1 0 0,0 1 0,1 1 0)),((0 0 1,0 0 0,0 1 0,0 0 1)),((0 1 0,0 1 1,0 0 1,0 1 0)),((0 0 1,0 0 0,1 0 0,0 0 1)),((1 0 0,1 0 1,0 0 1,1 0 0)),((1 1 1,1 0 1,0 1 1,1 1 1)),((0 0 1,0 1 1,1 0 1,0 0 1)),((1 1 0,1 1 1,1 0 1,1 1 0)),((1 0 1,1 0 0,1 1 0,1 0 1)),((1 1 1,1 1 0,0 1 1,1 1 1)),((0 1 0,0 1 1,1 1 0,0 1 0)))
Sample result triangulation with interior rings:
Sample with multiple interior rings:
- Input wkb must be of type PolyhedralSurface/MultiPolygon/Polygon, otherwise an error will occur;
- Triangulated geometry is returned as WKB (as PolyhedralSurface/MultiPolygon);
3D Triangulation is performed in 2D mode, by projecting each input polygon to yz, zx or xy plane. The plane to project to is determined by the normal vector of the input polygon.
Pseudo code for calculating plane to project to (nb: using absolute normals here):
yz: when (normal(x) > normal(y)) and (normal(x) > normal(z))
zx: else when (normal(y) > normal(z))
xy: all other cases
For triangulation the fast Earcut method is used. After triangulation the resulting triangles are 'unflattened' to get the 3D triangles.
After that, each triangle is checked to have the same direction as the original polygon by calculating the dot product between the normal of the polygon and the normal of the triangle. If the dot product is negative, then the two vectors point in opposite directions and the triangle will be inverted.
Triangles of (multi)lines can be calculate using the Triangulate method using the following parameters:
-
(Multi)LineString lineString: line geometry
-
float radius = 1
-
int radialSegments = 8
-
bool closed = false
A port of Three.JS TubeGeometry (https://github.com/hjoykim/THREE/) is used to calculate the mesh.
Sample code:
var wkt = "LINESTRING(-10 0 0,0 0 0,0 10 0)";
var line = (LineString)Geometry.Deserialize<WktSerializer>(wkt);
var triangles = Triangulator.Triangulate(line,2);
todo
In the unit test there is an conversion method from triangles to glTF 2.0 using SharpGLTF (https://github.com/vpenades/SharpGLTF) for visual inspections.
wkx-sharp - https://github.com/cschwarz/wkx-sharp for handling geometries
2024-09-03: release 1.5.2: fix interior rings triangulation
2024-08-08: release 1.5.1: add support for lines without z (assuming z=0)
2024-07-30: release 1.5.0: to .NET 8 + use LineCurve instead of CatmullRomCurve (better performance + more accurate)
2024-02-20: release 1.4.3: fix lines of 2 points
2024-02-20: release 1.4.2: add multi-line support
2024-02-14: release 1.4.1: make tubularSegments and radialSegments optional
2024-02-14: release 1.4.0: add support for lines
2024-02-07: release 1.3.1: normals algorithm fix for higher precision
2024-02-07: release 1.3.0: add support for interior rings + polygons
2023-09-26: release 1.2.3: fix normal close to 0
2023-09-22: release 1.2.2: fix normals calculation
2023-08-30: release 1.2.1: add support for Geometry type as input (in addition of WKB)
2023-08-30: release 1.2: add support for MultiPolygon
2020-09-01: release 1.1: to NET 6
2020-06-10: release 1.0.3
2020-06-09: release 1.0.2
2020-06-08: release 1.0.1
2020-06-07: release 1.0.0 Initial release