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LineSegment3d Struct

Overview

The LineSegment3d struct represents a bounded line segment in 3D space, defined by start and end points.

Namespace

Autodesk.AutoCAD.Geometry

Key Properties

Property Type Description
StartPoint Point3d Gets the start point of the segment
EndPoint Point3d Gets the end point of the segment
MidPoint Point3d Gets the midpoint of the segment
Direction Vector3d Gets the direction vector from start to end
Length double Gets the length of the segment

Constructors

Constructor Description
LineSegment3d(Point3d, Point3d) Creates segment from start and end points

Key Methods

Method Return Type Description
GetClosestPointTo(Point3d) Point3d Gets closest point on segment to given point
DistanceTo(Point3d) double Gets distance from point to segment
IsOn(Point3d) bool Checks if point is on segment
IsParallelTo(LineSegment3d) bool Checks if parallel to another segment
IsPerpendicularTo(LineSegment3d) bool Checks if perpendicular to another segment

Code Examples

Example 1: Creating Line Segments

Point3d start = new Point3d(0, 0, 0);
Point3d end = new Point3d(10, 10, 0);
LineSegment3d segment = new LineSegment3d(start, end);

ed.WriteMessage($"\nLength: {segment.Length:F2}");
ed.WriteMessage($"\nMidpoint: {segment.MidPoint}");
ed.WriteMessage($"\nDirection: {segment.Direction}");

Example 2: Point-to-Segment Distance

LineSegment3d segment = new LineSegment3d(
    new Point3d(0, 0, 0),
    new Point3d(10, 0, 0)
);

Point3d testPoint = new Point3d(5, 5, 0);
double distance = segment.DistanceTo(testPoint);
Point3d closestPoint = segment.GetClosestPointTo(testPoint);

ed.WriteMessage($"\nDistance to segment: {distance:F2}");
ed.WriteMessage($"\nClosest point: {closestPoint}");

Example 3: Checking if Point is on Segment

LineSegment3d segment = new LineSegment3d(
    new Point3d(0, 0, 0),
    new Point3d(10, 0, 0)
);

Point3d pt1 = new Point3d(5, 0, 0); // On segment
Point3d pt2 = new Point3d(15, 0, 0); // Beyond end
Point3d pt3 = new Point3d(5, 5, 0); // Off segment

bool isOn1 = segment.IsOn(pt1); // true
bool isOn2 = segment.IsOn(pt2); // false
bool isOn3 = segment.IsOn(pt3); // false

ed.WriteMessage($"\nPoint 1 on segment: {isOn1}");
ed.WriteMessage($"\nPoint 2 on segment: {isOn2}");
ed.WriteMessage($"\nPoint 3 on segment: {isOn3}");

Related Classes

  • Line3d - Unbounded 3D line
  • Point3d - Start/end points
  • Vector3d - Direction vector
  • LineSegment2d - 2D line segment

References