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Polyline3d.md

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Polyline3d Class

Overview

The Polyline3d class represents a piecewise linear spline entity in 3D space. Unlike smooth splines, polylines consist of straight line segments connecting vertices.

Namespace

Autodesk.AutoCAD.Geometry

Key Properties

Property Type Description
Vertices Point3dCollection Gets the vertices of the polyline
NumVertices int Gets the number of vertices
IsClosed bool Checks if polyline is closed

Key Methods

Method Return Type Description
GetClosestPointTo(Point3d) Point3d Gets closest point on polyline
GetSegmentAt(int) LineSegment3d Gets line segment at index
Length double Gets total length of polyline

Code Examples

Example 1: Creating 3D Polyline

Point3dCollection vertices = new Point3dCollection();
vertices.Add(new Point3d(0, 0, 0));
vertices.Add(new Point3d(10, 0, 0));
vertices.Add(new Point3d(10, 10, 0));
vertices.Add(new Point3d(0, 10, 5));

Polyline3d polyline = new Polyline3d(vertices, false); // not closed

ed.WriteMessage($"\n3D Polyline with {polyline.NumVertices} vertices");

Example 2: Closed Polyline

Point3dCollection vertices = new Point3dCollection();
vertices.Add(new Point3d(0, 0, 0));
vertices.Add(new Point3d(10, 0, 0));
vertices.Add(new Point3d(10, 10, 0));
vertices.Add(new Point3d(0, 10, 0));

Polyline3d closedPolyline = new Polyline3d(vertices, true); // closed

ed.WriteMessage($"\nClosed polyline: {closedPolyline.IsClosed}");

Best Practices

  1. Piecewise Linear: Straight segments, not smooth
  2. Closed: Set to true for closed shapes
  3. Vertices: Minimum 2 vertices required
  4. Approximation: Use to approximate smooth curves

Related Classes

  • Polyline2d - 2D polyline
  • LineSegment3d - Individual segments
  • CubicSplineCurve3d - Smooth alternative

References