/// <summary>
/// Creates a builder for linear elements which may be present
/// in the overlay result.
/// </summary>
/// <param name="inputGeom">The input geometries</param>
/// <param name="graph">The topology graph</param>
/// <param name="hasResultArea"><c>true</c> if an area has been generated for the result</param>
/// <param name="opCode">The overlay operation code</param>
/// <param name="geomFact">The output geometry factory</param>
public LineBuilder(InputGeometry inputGeom, OverlayGraph graph, bool hasResultArea, SpatialFunction opCode, GeometryFactory geomFact)
{
_graph = graph;
_opCode = opCode;
_geometryFactory = geomFact;
_hasResultArea = hasResultArea;
_inputAreaIndex = inputGeom.GetAreaIndex();
}
/// <summary>
/// Computes a clipping envelope for overlay input geometries.
/// The clipping envelope encloses all geometry line segments which
/// might participate in the overlay, with a buffer to
/// account for numerical precision
/// (in particular, rounding due to a precision model.
/// The clipping envelope is used in both the <see cref="RingClipper"/>
/// and in the <see cref="LineLimiter"/>.
/// <para/>
/// Some overlay operations (i.e. <see cref="SpatialFunction.Union"/> and <see cref="SpatialFunction.SymDifference"/>)
/// cannot use clipping as an optimization,
/// since the result envelope is the full extent of the two input geometries.
/// In this case the returned
/// envelope is <c>null</c> to indicate this.
/// </summary>
/// <param name="opCode">The overlay op code</param>
/// <param name="inputGeom">The input geometries</param>
/// <param name="pm">The precision model being used</param>
/// <returns>An envelope for clipping and line limiting, or null if no clipping is performed</returns>
internal static Envelope ClippingEnvelope(SpatialFunction opCode, InputGeometry inputGeom, PrecisionModel pm)
{
var resultEnv = ResultEnvelope(opCode, inputGeom, pm);
if (resultEnv == null)
{
return(null);
}
var clipEnv = RobustClipEnvelopeComputer.GetEnvelope(
inputGeom.GetGeometry(0),
inputGeom.GetGeometry(1),
resultEnv);
var safeEnv = SafeEnv(clipEnv, pm);
return(safeEnv);
}
/// <summary>
/// Computes an envelope which covers the extent of the result of
/// a given overlay operation for given inputs.
/// The operations which have a result envelope smaller than the extent of the inputs
/// are:
/// <list type="bullet">
/// <item><term><see cref="SpatialFunction.Intersection"/></term>
/// <description>result envelope is the intersection of the input envelopes</description></item>
/// <item><term><see cref="SpatialFunction.Difference"/></term>
/// <description>result envelope is the envelope of the A input geometry</description></item>
/// </list>
/// Otherwise, <c>null</c> is returned to indicate full extent.
/// </summary>
/// <param name="opCode">The overlay op code</param>
/// <param name="inputGeom">The input geometries</param>
/// <param name="pm">The precision model being used</param>
/// <returns>The result envelope, or null if the full extent</returns>
private static Envelope ResultEnvelope(SpatialFunction opCode, InputGeometry inputGeom, PrecisionModel pm)
{
Envelope overlapEnv = null;
switch (opCode)
{
case OverlayNG.INTERSECTION:
var envA = SafeEnv(inputGeom.GetEnvelope(0), pm);
var envB = SafeEnv(inputGeom.GetEnvelope(1), pm);
overlapEnv = envA.Intersection(envB);
break;
case OverlayNG.DIFFERENCE:
overlapEnv = SafeEnv(inputGeom.GetEnvelope(0), pm);
break;
}
// return null for UNION and SYMDIFFERENCE to indicate no clipping
return(overlapEnv);
}
/// <summary>
/// Creates an overlay operation on the given geometries,
/// with a defined precision model.
/// </summary>
/// <param name="geom0">The A operand geometry</param>
/// <param name="geom1">The B operand geometry (may be <c>null</c>)</param>
/// <param name="pm">The precision model to use</param>
/// <param name="opCode">The overlay opcode</param>
public OverlayNG(Geometry geom0, Geometry geom1, PrecisionModel pm, SpatialFunction opCode)
{
if (geom0 == null)
{
throw new ArgumentNullException(nameof(geom0));
}
switch (opCode)
{
case SpatialFunction.Intersection:
case SpatialFunction.Union:
case SpatialFunction.Difference:
case SpatialFunction.SymDifference:
break;
default:
throw new ArgumentOutOfRangeException(nameof(opCode), opCode, "Only Intersection, Union, Difference, and SymDifference are recognized at this time.");
}
_pm = pm;
_opCode = opCode;
_geomFact = geom0.Factory;
_inputGeom = new InputGeometry(geom0, geom1);
}
public OverlayLabeller(OverlayGraph graph, InputGeometry inputGeometry)
{
_graph = graph;
_inputGeometry = inputGeometry;
_edges = graph.Edges;
}
