private static void AdjustResultForIntersectionWithSide( ref Nullable<Point> result, ref double distance, Segment intersection, Point point )
{
if( !intersection.IsEmpty )
{
if( intersection.Contains( point ) )
{
distance = 0;
result = point;
return;
}
double p1Distance = PointHelper.DistanceBetween( point, intersection.P1 );
double p2Distance = double.PositiveInfinity;
if( !intersection.IsPoint )
{
p2Distance = PointHelper.DistanceBetween( point, intersection.P2 );
}
if( Math.Min( p1Distance, p2Distance ) < distance )
{
if( p1Distance < p2Distance )
{
distance = p1Distance;
result = intersection.P1;
}
else
{
distance = p2Distance;
result = intersection.P2;
}
}
}
}
private static void AdjustResultForIntersectionWithSide(ref Nullable <Point> result, ref double distance, Segment intersection, Point point)
{
if (!intersection.IsEmpty)
{
if (intersection.Contains(point))
{
distance = 0;
result = point;
return;
}
double p1Distance = PointHelper.DistanceBetween(point, intersection.P1);
double p2Distance = double.PositiveInfinity;
if (!intersection.IsPoint)
{
p2Distance = PointHelper.DistanceBetween(point, intersection.P2);
}
if (Math.Min(p1Distance, p2Distance) < distance)
{
if (p1Distance < p2Distance)
{
distance = p1Distance;
result = intersection.P1;
}
else
{
distance = p2Distance;
result = intersection.P2;
}
}
}
}
public Segment Intersection(Segment segment)
{
// if either segment is empty, the intersection is also empty
if (this.IsEmpty || segment.IsEmpty)
{
return(Segment.Empty);
}
// if the segments are equal, just return a new equal segment
if (this == segment)
{
return(new Segment(this._p1, this._p2, this._isP1Excluded, this._isP2Excluded));
}
// if either segment is a Point, just see if the point is contained in the other segment
if (this.IsPoint)
{
return(segment.Contains(this._p1) ? new Segment(this._p1) : Segment.Empty);
}
if (segment.IsPoint)
{
return(this.Contains(segment._p1) ? new Segment(segment._p1) : Segment.Empty);
}
// okay, no easy answer, so let's do the math...
Point p1 = this._p1;
Vector v1 = this._p2 - this._p1;
Point p2 = segment._p1;
Vector v2 = segment._p2 - segment._p1;
Vector endpointVector = p2 - p1;
double xProd = Vector.CrossProduct(v1, v2);
// if segments are not parallel, then look for intersection on each segment
if (!DoubleHelper.AreVirtuallyEqual(Slope, segment.Slope))
{
// check for intersection on other segment
double s = (Vector.CrossProduct(endpointVector, v1)) / xProd;
if (s < 0 || s > 1)
{
return(Segment.Empty);
}
// check for intersection on this segment
s = (Vector.CrossProduct(endpointVector, v2)) / xProd;
if (s < 0 || s > 1)
{
return(Segment.Empty);
}
// intersection of segments is a point
return(new Segment(p1 + s * v1));
}
// segments are parallel
xProd = Vector.CrossProduct(endpointVector, v1);
if (xProd * xProd > 1.0e-06 * v1.LengthSquared * endpointVector.LengthSquared)
{
// segments do not intersect
return(Segment.Empty);
}
// intersection is overlapping segment
Segment result = new Segment();
// to determine the overlapping segment, create reference segments where the endpoints are *not* excluded
Segment refThis = new Segment(this._p1, this._p2);
Segment refSegment = new Segment(segment._p1, segment._p2);
// check whether this segment is contained in the other segment
bool includeThisP1 = refSegment.Contains(refThis._p1);
bool includeThisP2 = refSegment.Contains(refThis._p2);
if (includeThisP1 && includeThisP2)
{
result._p1 = this._p1;
result._p2 = this._p2;
result._isP1Excluded = this._isP1Excluded || !segment.Contains(this._p1);
result._isP2Excluded = this._isP2Excluded || !segment.Contains(this._p2);
return(result);
}
// check whether the other segment is contained in this segment
bool includeSegmentP1 = refThis.Contains(refSegment._p1);
bool includeSegmentP2 = refThis.Contains(refSegment._p2);
if (includeSegmentP1 && includeSegmentP2)
{
result._p1 = segment._p1;
result._p2 = segment._p2;
result._isP1Excluded = segment._isP1Excluded || !this.Contains(segment._p1);
result._isP2Excluded = segment._isP2Excluded || !this.Contains(segment._p2);
return(result);
}
// the intersection must include one endpoint from this segment and one endpoint from the other segment
if (includeThisP1)
{
result._p1 = this._p1;
result._isP1Excluded = this._isP1Excluded || !segment.Contains(this._p1);
}
else
{
result._p1 = this._p2;
result._isP1Excluded = this._isP2Excluded || !segment.Contains(this._p2);
}
if (includeSegmentP1)
{
result._p2 = segment._p1;
result._isP2Excluded = segment._isP1Excluded || !this.Contains(segment._p1);
}
else
{
result._p2 = segment._p2;
result._isP2Excluded = segment._isP2Excluded || !this.Contains(segment._p2);
}
return(result);
}
public Segment Intersection( Segment segment )
{
// if either segment is empty, the intersection is also empty
if( this.IsEmpty || segment.IsEmpty )
return Segment.Empty;
// if the segments are equal, just return a new equal segment
if( this == segment )
return new Segment( this._p1, this._p2, this._isP1Excluded, this._isP2Excluded );
// if either segment is a Point, just see if the point is contained in the other segment
if( this.IsPoint )
return segment.Contains( this._p1 ) ? new Segment( this._p1 ) : Segment.Empty;
if( segment.IsPoint )
return this.Contains( segment._p1 ) ? new Segment( segment._p1 ) : Segment.Empty;
// okay, no easy answer, so let's do the math...
Point p1 = this._p1;
Vector v1 = this._p2 - this._p1;
Point p2 = segment._p1;
Vector v2 = segment._p2 - segment._p1;
Vector endpointVector = p2 - p1;
double xProd = Vector.CrossProduct( v1, v2 );
// if segments are not parallel, then look for intersection on each segment
if( !DoubleHelper.AreVirtuallyEqual( Slope, segment.Slope ) )
{
// check for intersection on other segment
double s = ( Vector.CrossProduct( endpointVector, v1 ) ) / xProd;
if( s < 0 || s > 1 )
return Segment.Empty;
// check for intersection on this segment
s = ( Vector.CrossProduct( endpointVector, v2 ) ) / xProd;
if( s < 0 || s > 1 )
return Segment.Empty;
// intersection of segments is a point
return new Segment( p1 + s * v1 );
}
// segments are parallel
xProd = Vector.CrossProduct( endpointVector, v1 );
if( xProd * xProd > 1.0e-06 * v1.LengthSquared * endpointVector.LengthSquared )
{
// segments do not intersect
return Segment.Empty;
}
// intersection is overlapping segment
Segment result = new Segment();
// to determine the overlapping segment, create reference segments where the endpoints are *not* excluded
Segment refThis = new Segment( this._p1, this._p2 );
Segment refSegment = new Segment( segment._p1, segment._p2 );
// check whether this segment is contained in the other segment
bool includeThisP1 = refSegment.Contains( refThis._p1 );
bool includeThisP2 = refSegment.Contains( refThis._p2 );
if( includeThisP1 && includeThisP2 )
{
result._p1 = this._p1;
result._p2 = this._p2;
result._isP1Excluded = this._isP1Excluded || !segment.Contains( this._p1 );
result._isP2Excluded = this._isP2Excluded || !segment.Contains( this._p2 );
return result;
}
// check whether the other segment is contained in this segment
bool includeSegmentP1 = refThis.Contains( refSegment._p1 );
bool includeSegmentP2 = refThis.Contains( refSegment._p2 );
if( includeSegmentP1 && includeSegmentP2 )
{
result._p1 = segment._p1;
result._p2 = segment._p2;
result._isP1Excluded = segment._isP1Excluded || !this.Contains( segment._p1 );
result._isP2Excluded = segment._isP2Excluded || !this.Contains( segment._p2 );
return result;
}
// the intersection must include one endpoint from this segment and one endpoint from the other segment
if( includeThisP1 )
{
result._p1 = this._p1;
result._isP1Excluded = this._isP1Excluded || !segment.Contains( this._p1 );
}
else
{
result._p1 = this._p2;
result._isP1Excluded = this._isP2Excluded || !segment.Contains( this._p2 );
}
if( includeSegmentP1 )
{
result._p2 = segment._p1;
result._isP2Excluded = segment._isP1Excluded || !this.Contains( segment._p1 );
}
else
{
result._p2 = segment._p2;
result._isP2Excluded = segment._isP2Excluded || !this.Contains( segment._p2 );
}
return result;
}