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@Const-me Const-me/Lines.cs
Created Jul 27, 2018

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using System.Windows;
// Base class for lines
abstract class LineBase
{
// First and second point of the line
public readonly Point p0, p2;
public override string ToString()
{
return $"{{ {p0} }} -> {{ {p2} }}";
}
protected LineBase( Point a, Point b )
{
if( !( a - b ).LengthSquared.isNormal() )
throw new ArgumentException( "The points are too close, they don't define a line." );
p0 = a;
p2 = b;
}
// Test if the parameter is inside the line.
protected abstract bool isInside( double param );
// Intersection algorithm goes here
public bool intersects( LineBase that, out double paramThis, out double paramThat ) { ... }
// Returns p0 * ( 1.0 - param ) + p2 * param
public Point at( double param ) { ... }
}
class Line : LineBase
{
public Line( Point a, Point b ) : base( a, b ) { }
protected override bool isInside( double param )
{
// Lines are infinite in both directions
return true;
}
}
class Ray : LineBase
{
public Ray( Point a, Point b ) : base( a, b ) { }
protected override bool isInside( double param )
{
// Rays are infinite in one direction
return param >= -0.0;
}
}
class Segment : LineBase
{
public Segment( Point a, Point b ) : base( a, b ) { }
protected override bool isInside( double param )
{
// Segments are limited on both ends.
return param >= -0.0 && param <= 1.0;
}
}
static class LinesExt
{
public static double? intersectionParam( this LineBase i, LineBase that )
{
bool res = i.intersects( that, out double m0, out double m2 );
if( !res )
return null;
return m0;
}
public static Point? intersectionPoint( this LineBase i, LineBase that )
{
bool res = i.intersects( that, out double m0, out double m2 );
if( !res )
return null;
return i.at( m0 );
}
public static bool intersects( this LineBase i, LineBase that )
{
return i.intersects( that, out double m0, out double m2 );
}
}
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