} // private void LabelIntersectionNodes( int argIndex )
/// <summary>
/// If the Geometries are disjoint, we need to enter their dimension and
/// boundary dimension in the Ext rows in the IM.
/// </summary>
/// <param name="im"></param>
private void ComputeDisjointIM( IntersectionMatrix im )
{
Geometry ga = _arg[0].Geometry;
if ( !ga.IsEmpty() )
{
im.Set( Location.Interior, Location.Exterior, ga.GetDimension() );
im.Set( Location.Boundary, Location.Exterior, ga.GetBoundaryDimension() );
}
Geometry gb = _arg[1].Geometry;
if ( !gb.IsEmpty() )
{
im.Set( Location.Exterior, Location.Interior, gb.GetDimension() );
im.Set( Location.Exterior, Location.Boundary, gb.GetBoundaryDimension() );
}
} // private void ComputeDisjointIM( IntersectionMatrix im )
} // public bool HasDuplicateRings()
/// <summary>
/// Computes the Intersection matrix for the geometries.
/// </summary>
/// <returns></returns>
public IntersectionMatrix ComputeIM()
{
IntersectionMatrix im = new IntersectionMatrix();
// since Geometries are finite and embedded in a 2-D space, the EE element must always be 2
im.Set( Location.Exterior, Location.Exterior, 2);
// if the Geometries don't overlap there is nothing to do
if ( !_arg[0].Geometry.GetEnvelopeInternal().Intersects(
_arg[1].Geometry.GetEnvelopeInternal() ) )
{
ComputeDisjointIM( im );
return im;
}
_arg[0].ComputeSelfNodes( _li );
_arg[1].ComputeSelfNodes( _li );
// compute intersections between edges of the two input geometries
SegmentIntersector intersector = _arg[0].ComputeEdgeIntersections( _arg[1], _li, false );
ComputeIntersectionNodes(0);
ComputeIntersectionNodes(1);
// Copy the labelling for the nodes in the parent Geometries. These override
// any labels determined by intersections between the geometries.
CopyNodesAndLabels(0);
CopyNodesAndLabels(1);
// complete the labelling for any nodes which only have a label for a single geometry
LabelIsolatedNodes();
// If a proper intersection was found, we can set a lower bound on the IM.
ComputeProperIntersectionIM( intersector, im );
// Now process improper intersections
// (eg where one or other of the geometrys has a vertex at the intersection point)
// We need to compute the edge graph at all nodes to determine the IM.
// build EdgeEnds for all intersections
EdgeEndBuilder eeBuilder = new EdgeEndBuilder();
ArrayList ee0 = eeBuilder.ComputeEdgeEnds( _arg[0].Edges );
InsertEdgeEnds( ee0 );
ArrayList ee1 = eeBuilder.ComputeEdgeEnds( _arg[1].Edges );
InsertEdgeEnds( ee1 );
//Trace.WriteLine("==== NodeList ===");
//Trace.WriteLine( _nodes.ToString() );
LabelNodeEdges();
// Compute the labeling for isolated components
// <br>
// Isolated components are components that do not touch any other components in the graph.
// They can be identified by the fact that they will
// contain labels containing ONLY a single element, the one for their parent geometry.
// We only need to check components contained in the input graphs, since
// isolated components will not have been replaced by new components formed by intersections.
//Trace.WriteLine("Graph A isolated edges - ");
LabelIsolatedEdges(0, 1);
//Trace.WriteLine("Graph B isolated edges - ");
LabelIsolatedEdges(1, 0);
// update the IM from all components
UpdateIM( im );
return im;
} // public IntersectionMatrix ComputeIM()
