Segment

Introduction

A segment is a object defined by two Points. It is not a PositionedObject and its points are absolute, which differentiates it from the Line class.

Segment Intersection

The following code creates two Lines. One line rotates automatically while the other is controlled by input from the Keyboard. The two Lines call the AsSegment method to create Segments that represent the calling Lines. The segment can then be used to find the point of collision between the two Lines. If the resulting intersection point has valid coordinates then a collision has occurred. A red ball Sprite marks the intersection point between the two Lines.

Add the following using statements:

using FlatRedBall.Math.Geometry;
using FlatRedBall.Input;

Add the following at class scope:

Line firstLine;
Line secondLine;
Sprite sprite;

Add the following in Initialize after initializing FlatRedBall:

firstLine = ShapeManager.AddLine();
firstLine.RelativePoint1 = new Point3D(-5, 0);
firstLine.RelativePoint2 = new Point3D(5, 0);
firstLine.RotationZVelocity = 1;

secondLine = ShapeManager.AddLine();
secondLine.RelativePoint1 = new Point3D(-3, 0);
secondLine.RelativePoint2 = new Point3D(3, 0);

sprite = SpriteManager.AddSprite("redball.bmp");
sprite.ScaleX = sprite.ScaleY = .5f;

Add the following in Update:

InputManager.Keyboard.ControlPositionedObject(secondLine);

// To get the collision points, use Segments
Segment firstSegment = firstLine.AsSegment();
Segment secondSegment = secondLine.AsSegment();

// Qualify Point since there is a Microsoft.Xna.Framework.Point
FlatRedBall.Math.Geometry.Point intersectionPoint;

firstSegment.IntersectionPoint(ref secondSegment, out intersectionPoint);

if (double.IsNaN(intersectionPoint.X))
{
    sprite.Visible = false;
}
else
{
    sprite.Visible = true;
    sprite.X = (float)intersectionPoint.X;
    sprite.Y = (float)intersectionPoint.Y;
}

Intersection.png

Segment Members

• FlatRedBall.Math.Geometry.Segment.ClosestPointTo

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