CavalierContoursSharp

C# binding for cavalier_contours, a high-performance 2D polyline/shape library for offsetting, combining, and more. 1

Features

• High Performance: Built on the fast Rust cavalier_contours library 1
• Polyline Operations: Create, modify, and analyze 2D polylines with arc support
• Boolean Operations: Union (OR), Intersection (AND), Difference (NOT), and XOR operations
• Parallel Offsetting: Generate offset polylines with various join types
• Geometric Queries: Area calculation, path length, winding number, point-in-polygon tests
• Spatial Indexing: AABB (Axis-Aligned Bounding Box) indexing for fast spatial queries
• Memory Safe: Proper resource management with IDisposable pattern
• Cross-Platform: Supports Windows x64 (more platforms coming soon)

Installation

dotnet add package CavalierContoursSharp

Quick Start

Creating a Simple Polyline

using CavalierContoursSharp;

// Create an empty polyline
using var polyline = new Polyline();

// Add vertices
polyline.AddVertex(0, 0);
polyline.AddVertex(10, 0);
polyline.AddVertex(10, 10);
polyline.AddVertex(0, 10);

// Make it closed
polyline.IsClosed = true;

// Get properties
Console.WriteLine($"Area: {polyline.Area}");
Console.WriteLine($"Path Length: {polyline.PathLength}");
Console.WriteLine($"Vertex Count: {polyline.VertexCount}");

Creating Polylines with Arcs

// Create a polyline with arc segments using bulge values
var vertices = new[]
{
    new CavcVertex(0, 0, 0),      // Straight line to next vertex
    new CavcVertex(10, 0, 0.5),   // Arc to next vertex (bulge = 0.5)
    new CavcVertex(10, 10, 0),    // Straight line to next vertex
    new CavcVertex(0, 10, 0)      // Straight line back to start
};

using var polyline = new Polyline(vertices, true); // true = closed

Boolean Operations

// Create two overlapping squares
using var square1 = new Polyline(new[]
{
    new CavcVertex(0, 0),
    new CavcVertex(10, 0),
    new CavcVertex(10, 10),
    new CavcVertex(0, 10)
}, true);

using var square2 = new Polyline(new[]
{
    new CavcVertex(5, 5),
    new CavcVertex(15, 5),
    new CavcVertex(15, 15),
    new CavcVertex(5, 15)
}, true);

// Perform boolean operations
var (union, _) = square1.BooleanOperation(square2, BooleanOp.Or);
var (intersection, _) = square1.BooleanOperation(square2, BooleanOp.And);
var (difference, _) = square1.BooleanOperation(square2, BooleanOp.Not);
var (xor, _) = square1.BooleanOperation(square2, BooleanOp.Xor);

// Remember to dispose results
union.Dispose();
intersection.Dispose();
difference.Dispose();
xor.Dispose();

Parallel Offsetting

using var polyline = new Polyline(new[]
{
    new CavcVertex(0, 0),
    new CavcVertex(10, 0),
    new CavcVertex(10, 10),
    new CavcVertex(0, 10)
}, true);

// Create offset polylines
using var offsetResults = polyline.ParallelOffset(2.0); // Offset by 2 units

foreach (var offsetPolyline in offsetResults)
{
    Console.WriteLine($"Offset polyline area: {offsetPolyline.Area}");
    offsetPolyline.Dispose();
}

Geometric Queries

using var polyline = new Polyline(new[]
{
    new CavcVertex(0, 0),
    new CavcVertex(10, 0),
    new CavcVertex(10, 10),
    new CavcVertex(0, 10)
}, true);

// Point-in-polygon test
int windingNumber = polyline.GetWindingNumber(5, 5); // Inside: winding number = 1
int windingNumber2 = polyline.GetWindingNumber(15, 15); // Outside: winding number = 0

// Get bounding box
if (polyline.GetExtents(out double minX, out double minY, out double maxX, out double maxY))
{
    Console.WriteLine($"Bounds: ({minX}, {minY}) to ({maxX}, {maxY})");
}

// Transform operations
polyline.Scale(2.0);        // Scale by factor of 2
polyline.Translate(5, 5);   // Move by (5, 5)
polyline.InvertDirection(); // Reverse vertex order

Working with Vertices

using var polyline = new Polyline();

// Add vertices one by one
polyline.AddVertex(0, 0, 0);     // x, y, bulge
polyline.AddVertex(10, 0, 0.5);  // Arc segment
polyline.AddVertex(10, 10, 0);

// Get and modify vertices
var vertex = polyline.GetVertex(1);
vertex.Bulge = 0.2; // Change arc curvature
polyline.SetVertex(1, vertex);

// Get all vertices
var allVertices = polyline.GetVertices();

// Iterate through vertices
foreach (var v in polyline)
{
    Console.WriteLine($"Vertex: ({v.X}, {v.Y}), Bulge: {v.Bulge}");
}

Understanding Bulge Values

Bulge values define arc segments between vertices:

• bulge = 0: Straight line segment
• bulge > 0: Arc curves to the left (counter-clockwise)
• bulge < 0: Arc curves to the right (clockwise)
• bulge = 1: Perfect semicircle
• bulge = tan(θ/4) where θ is the arc's central angle

API Reference

Core Classes

• Polyline: Main class representing a 2D polyline with vertices and arcs
• CavcVertex: Structure representing a vertex with X, Y coordinates and bulge value
• PolylineList: Collection of polylines returned by boolean operations
• BooleanOp: Enumeration of boolean operation types (Or, And, Not, Xor)
• CavcAabbIndex: Spatial index for fast geometric queries

Key Methods

• Vertex Management: AddVertex(), GetVertex(), SetVertex(), RemoveVertex()
• Boolean Operations: BooleanOperation()
• Offsetting: ParallelOffset()
• Geometric Queries: GetWindingNumber(), GetExtents(), Area, PathLength
• Transformations: Scale(), Translate(), InvertDirection()
• Spatial Indexing: CreateAabbIndex(), CreateApproximateAabbIndex()

Performance Notes

• Always dispose of Polyline and PolylineList objects to free native memory
• Use using statements for automatic disposal
• Boolean operations and offsetting can return multiple result polylines
• AABB indexing significantly speeds up spatial queries for complex polylines

Platform Support

• Windows x64: ✅ Fully supported
• Linux x64: 🚧 Coming soon
• macOS: 🚧 Coming soon

Contributing

Contributions are welcome! Please feel free to submit issues and pull requests.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Related Projects

• cavalier_contours - The original Rust library 1
• Interactive Web Demo - Try the library online 5