NurbsSharp 0.1.1

NURBS Sharp

NURBS Sharp is a small, dependency-free NURBS (Non-Uniform Rational B-Spline) library for .NET. It provides data structures, evaluators, topology operators, I/O and tessellation utilities implemented using only the .NET standard library.

Japanese Readme

Table of Contents

• Features
• Installation
• Quick Start
• Examples
• Documentation
• Development
• Contributing
• Code of Conduct
• License

Features

• Generation and evaluation of NURBS curves and surfaces
• Topology operators: degree, knot insertion/removal, join/split
• IO helpers: simple OBJ/STL export for ONLY Mesh, IGES import / export for ONLY NURBS, simple BMP export
• Tessellation utilities for curves and surfaces
• Targets: .NET 8 and .NET Standard 2.1

Limitations

• Knot Vector: Currently, only "Clamped" knot vectors are supported (multiplicity = degree + 1).
• Topology Operations: JoinSurface are not yet implemented.
• IGES Support:
  • Import: Only supports Entity Type 126 (Rational B-spline curve) and 128 (Rational B-spline surface).
  • Export: Only supports NURBS entities. Mesh export is not supported.
• Mesh Export (OBJ/STL): Only supports Mesh objects. Direct export from NURBS is not supported (tessellation required).
• Generation: Approximation is not implemented yet (only Interpolation is available).

Installation

Install via NuGet:

dotnet add package NurbsSharp

Or add the package reference to your project file.

Quick Start

Basic usage (C#):

using NurbsSharp.Core;
using NurbsSharp.Geometry;
using NurbsSharp.Tesselation;
using NurbsSharp.IO;

// Create a NURBS surface and evaluate a point
int degreeU = 3, degreeV = 3;
var knotsU = new double[] {0,0,0,0,1,1,1,1};
var knotsV = new double[] {0,0,0,0,1,1,1,1};
var kvU = new KnotVector(knotsU);
var kvV = new KnotVector(knotsV);

// Build control points (u x v grid)
ControlPoint[][] controlPoints = new ControlPoint[4][];
controlPoints[0] = new ControlPoint[] {
    new ControlPoint(0.0, 0.0, 0.0, 1),
    new ControlPoint(1.0, 0.0, 1.0, 1),
    new ControlPoint(2.0, 0.0, 3.0, 1),
    new ControlPoint(3.0, 0.0, 3.0, 1)
};
// ... Create Control Points ...

var surface = new NurbsSurface(degreeU, degreeV, kvU, kvV, controlPoints);
var point = surface.GetPos(0.5, 0.5);
Console.WriteLine(point);

Examples

tessellate a surface and export to STL:

int divideN = 20;
var mesh = SurfaceTessellator.Tessellate(surface, divideN, divideN);
using (var fs = new FileStream("test_output.stl", FileMode.Create, FileAccess.Write))
{
    await STLExporter.ExportAsync(mesh, fs);
}

Examples Project: https://github.com/nyarurato/NurbsSharpSample
Github Wiki: https://github.com/nyarurato/NurbsSharp/wiki/Samples

Documentation

API Docs: https://nyarurato.github.io/NurbsSharp/

Development

Clone the repo and build locally:

dotnet restore
dotnet build -c Debug

Run unit tests:

dotnet test -c Debug

Project layout highlights:

• src/Core — numeric helpers and core types
• src/Geometry — NurbsCurve, NurbsSurface, Mesh etc.
• src/Evaluation — curve/surface evaluators
• src/Operation — topology operators (degree, knot, join, split)
• src/IO — OBJExporter, STLExporter, minimal IGES helpers

Contributing

Contributions are welcome. Typical workflow:

1. Fork the repository
2. Create a branch with a descriptive name
3. Add tests for new behavior where appropriate
4. Open a pull request against main (or the target branch used in this repo)

License

MIT License