LibTessDotNet 1.1.15

dotnet add package LibTessDotNet --version 1.1.15
NuGet\Install-Package LibTessDotNet -Version 1.1.15
This command is intended to be used within the Package Manager Console in Visual Studio, as it uses the NuGet module's version of Install-Package.
<PackageReference Include="LibTessDotNet" Version="1.1.15" />
For projects that support PackageReference, copy this XML node into the project file to reference the package.
paket add LibTessDotNet --version 1.1.15
#r "nuget: LibTessDotNet, 1.1.15"
#r directive can be used in F# Interactive and Polyglot Notebooks. Copy this into the interactive tool or source code of the script to reference the package.
// Install LibTessDotNet as a Cake Addin
#addin nuget:?package=LibTessDotNet&version=1.1.15

// Install LibTessDotNet as a Cake Tool
#tool nuget:?package=LibTessDotNet&version=1.1.15

LibTessDotNet Build Status


Provide a robust and fast tessellator (polygons with N vertices in the output) for .NET, also does triangulation.


  • .NET Standard 2.0 (see here for more information)


  • Tessellate arbitrary complex polygons
    • self-intersecting (see "star-intersect" sample)
    • with coincident vertices (see "clipper" sample)
    • advanced winding rules : even/odd, non zero, positive, negative, |winding| >= 2 (see "redbook-winding" sample)
  • Custom input
    • Custom vertex attributes (eg. UV coordinates) with merging callback
    • Force orientation of input contour (clockwise/counterclockwise, eg. for GIS systems, see "force-winding" sample)
  • Choice of output
    • polygons with N vertices (with N >= 3)
    • connected polygons (didn't quite tried this yet, but should work)
    • boundary only (to have a basic union of two contours)
  • Handles polygons computed with Clipper - an open source freeware polygon clipping library
  • Single/Double precision support


Redbook winding example




dotnet build


From TessExample/Program.cs

using LibTessDotNet;
using System;
using System.Drawing;

namespace TessExample
    class Program
        // The data array contains 4 values, it's the associated data of the vertices that resulted in an intersection.
        private static object VertexCombine(LibTessDotNet.Vec3 position, object[] data, float[] weights)
            // Fetch the vertex data.
            var colors = new Color[] { (Color)data[0], (Color)data[1], (Color)data[2], (Color)data[3] };
            // Interpolate with the 4 weights.
            var rgba = new float[] {
                (float)colors[0].R * weights[0] + (float)colors[1].R * weights[1] + (float)colors[2].R * weights[2] + (float)colors[3].R * weights[3],
                (float)colors[0].G * weights[0] + (float)colors[1].G * weights[1] + (float)colors[2].G * weights[2] + (float)colors[3].G * weights[3],
                (float)colors[0].B * weights[0] + (float)colors[1].B * weights[1] + (float)colors[2].B * weights[2] + (float)colors[3].B * weights[3],
                (float)colors[0].A * weights[0] + (float)colors[1].A * weights[1] + (float)colors[2].A * weights[2] + (float)colors[3].A * weights[3]
            // Return interpolated data for the new vertex.
            return Color.FromArgb((int)rgba[3], (int)rgba[0], (int)rgba[1], (int)rgba[2]);

        static void Main(string[] args)
            // Example input data in the form of a star that intersects itself.
            var inputData = new float[] { 0.0f, 3.0f, -1.0f, 0.0f, 1.6f, 1.9f, -1.6f, 1.9f, 1.0f, 0.0f };

            // Create an instance of the tessellator. Can be reused.
            var tess = new LibTessDotNet.Tess();

            // Construct the contour from inputData.
            // A polygon can be composed of multiple contours which are all tessellated at the same time.
            int numPoints = inputData.Length / 2;
            var contour = new LibTessDotNet.ContourVertex[numPoints];
            for (int i = 0; i < numPoints; i++)
                // NOTE : Z is here for convenience if you want to keep a 3D vertex position throughout the tessellation process but only X and Y are important.
                contour[i].Position = new LibTessDotNet.Vec3(inputData[i * 2], inputData[i * 2 + 1], 0);
                // Data can contain any per-vertex data, here a constant color.
                contour[i].Data = Color.Azure;
            // Add the contour with a specific orientation, use "Original" if you want to keep the input orientation.
            tess.AddContour(contour, LibTessDotNet.ContourOrientation.Clockwise);

            // Tessellate!
            // The winding rule determines how the different contours are combined together.
            // See (section "Winding Numbers and Winding Rules") for more information.
            // If you want triangles as output, you need to use "Polygons" type as output and 3 vertices per polygon.
            tess.Tessellate(LibTessDotNet.WindingRule.EvenOdd, LibTessDotNet.ElementType.Polygons, 3, VertexCombine);

            // Same call but the last callback is optional. Data will be null because no interpolated data would have been generated.
            //tess.Tessellate(LibTessDotNet.WindingRule.EvenOdd, LibTessDotNet.ElementType.Polygons, 3); // Some vertices will have null Data in this case.

            Console.WriteLine("Output triangles:");
            int numTriangles = tess.ElementCount;
            for (int i = 0; i < numTriangles; i++)
                var v0 = tess.Vertices[tess.Elements[i * 3]].Position;
                var v1 = tess.Vertices[tess.Elements[i * 3 + 1]].Position;
                var v2 = tess.Vertices[tess.Elements[i * 3 + 2]].Position;
                Console.WriteLine("#{0} ({1:F1},{2:F1}) ({3:F1},{4:F1}) ({5:F1},{6:F1})", i, v0.X, v0.Y, v1.X, v1.Y, v2.X, v2.Y);


  • When using ElementType.BoundaryContours, Tess.Elements will contain a list of ranges [startVertexIndex, vertexCount]. Those ranges are to used with Tess.Vertices.


  • No allocations with the same input twice, all coming from pool
  • Any suggestions are welcome 😉


SGI FREE SOFTWARE LICENSE B (Version 2.0, Sept. 18, 2008) More information in LICENSE.txt.

  • Reference implementation - the original SGI reference implementation
  • libtess2 - Mikko Mononen cleaned up the original GLU tesselator
  • Poly2Tri - another triangulation library for .NET (other ports also available)
    • Does not support polygons from Clipper, more specifically vertices with same coordinates (coincident)
  • Clipper - an open source freeware polygon clipping library
Product Compatible and additional computed target framework versions.
.NET net5.0 was computed.  net5.0-windows was computed.  net6.0 was computed.  net6.0-android was computed.  net6.0-ios was computed.  net6.0-maccatalyst was computed.  net6.0-macos was computed.  net6.0-tvos was computed.  net6.0-windows was computed.  net7.0 was computed.  net7.0-android was computed.  net7.0-ios was computed.  net7.0-maccatalyst was computed.  net7.0-macos was computed.  net7.0-tvos was computed.  net7.0-windows was computed.  net8.0 was computed.  net8.0-android was computed.  net8.0-browser was computed.  net8.0-ios was computed.  net8.0-maccatalyst was computed.  net8.0-macos was computed.  net8.0-tvos was computed.  net8.0-windows was computed. 
.NET Core netcoreapp2.0 was computed.  netcoreapp2.1 was computed.  netcoreapp2.2 was computed.  netcoreapp3.0 was computed.  netcoreapp3.1 was computed. 
.NET Standard netstandard2.0 is compatible.  netstandard2.1 was computed. 
.NET Framework net461 was computed.  net462 was computed.  net463 was computed.  net47 was computed.  net471 was computed.  net472 was computed.  net48 was computed.  net481 was computed. 
MonoAndroid monoandroid was computed. 
MonoMac monomac was computed. 
MonoTouch monotouch was computed. 
Tizen tizen40 was computed.  tizen60 was computed. 
Xamarin.iOS xamarinios was computed. 
Xamarin.Mac xamarinmac was computed. 
Xamarin.TVOS xamarintvos was computed. 
Xamarin.WatchOS xamarinwatchos was computed. 
Compatible target framework(s)
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Learn more about Target Frameworks and .NET Standard.

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Work with discrete 2D shapes with and without curves


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Version Downloads Last updated
1.1.15 51,762 3/17/2021
1.1.13 19,417 2/15/2020
1.1.12 588 2/15/2020