BorderMatchOperator Class
Abstract base class for operators that combine polygon borders.
NuGet/Assembly: Carmenta.Engine.5.16.2.nupkg (in the CEOperators assembly)
Syntax
public abstract class BorderMatchOperator : UnaryOperatorRemarks
Polygons that should be adjacent will often differ slightly along their common border. This abstract base class provides tolerances that decide when polygons are adjacent enough, and which polygons that should be trusted.
Which polygon decides?
When two polygons disagree about their common border, one of them will decide where the border goes, by these rules:
The polygon with the smaller MaxDisplacement decides.
If the MaxDisplacement of the polygons are equal, then the polygon with the smaller MaxRotation decides.
If the polygons have equal MaxDisplacement and equal MaxRotation, then the polygon with the smaller area decides.
After one polygon has been chosen as the deciding one of two, its MaxDisplacement and MaxRotation become irrelevant along the border in question, since the edges of the deciding polygon will be neither displaced nor rotated. It will be the MaxDisplacement and the MaxRotation of the other polygon that are critical. But a polygon that decides over one neighboring polygon may have to yield to another of its neighbors.
If a RectangleClipOperator clips the input polygons, then the polygon areas that the BorderMatchOperator can compute will vary during panning and zooming. If you need a stable result, you can use a SizeOperator before the RectangleClipOperator, since the BorderMatchOperator will trust the area attribute created by SizeOperator.
Efficiency
The time it takes to match polygon borders increases with the number of corners that the polygons have, so if performance is a concern there are a few approaches that limits this number. When a large area is shown, you can let a LevelOfDetailOperator select low-resolution versions of your polygons (if available). You can also use a RectangleClipOperator and a LineThinningOperator to simplify the input. But note that the LineThinningOperator may move each polygon as much as the LineThinningOperator.MaxError, so you should increase the MaxDisplacement by twice the LineThinningOperator.MaxError.
Tolerances may depend on an accuracy class
A FunnelOperator can merge polygon streams from different sources into a single input stream for a BorderMatchOperator. If the accuracy of the polygons depends on their source, you may tag them with an accuracy attribute (before they reach the FunnelOperator). For example, to the left of a ReadOperator that gives accurate polygons, you can use an AttributeOperator to set an attribute "accuracyClass" to an integer value, and then set MaxDisplacement to a KeyedAttributeVariable<System.Double>, using the "accuracyClass" value to lookup the a numeric tolerance value. You could also also use an IndirectAttributeVariable<System.Double>, but this is not recommended for efficiency reasons; see note under MaxDisplacement.
Inheritance Hierarchy
System.Object (not available in C#)
EngineObject
Operator
UnaryOperator
BorderMatchOperator
BorderMergeOperator
BorderSnapOperator
Platforms
Windows, Linux, Android
BorderMatchOperator Members
The BorderMatchOperator type has the following members.
Properties
| Name | Description |
|---|---|
| Description | Gets or sets a short description of the operator. Inherited from Operator |
| DisplayName | Gets or sets a display name for the operator. Inherited from Operator |
| Input | Gets or sets the input operator, from which this operator reads features. Inherited from UnaryOperator |
| IsDisposed | Gets a value that tells whether the current BorderMatchOperator has been disposed. Inherited from EngineObject |
| IsoMetadataDocument | Gets or sets the path to an ISO 19139 metadata document for the operator. Inherited from Operator |
| MaxDisplacement | Gets or sets the maximum distance (in meters) that the border of a polygon may be displaced to fit another polygon. |
| MaxRotation | Gets or sets the largest angle that a polygon edge may be rotated to match the edge of another polygon. |
| Name | Gets or sets the name of the operator. Inherited from Operator |
| NativeHandle | Gets the native Carmenta Engine kernel object the current BorderMatchOperator represents. Inherited from EngineObject |
| ShortestGapFactor | Gets or sets a factor that, when multiplied with MaxDisplacement, gives the minimal gap between two pieces of border that are shared by the same two polygons. |
| ShortestMatchFactor | Gets or sets a factor that, when multiplied with MaxDisplacement, gives the minimal length of a border that will be regarded as shared with another polygon. |
| IUserProperties.UserProperties | Gets the AttributeSet that contains the user properties. Inherited from IUserProperties |
Methods
| Name | Description |
|---|---|
| Clone | Creates a copy of an object. Inherited from EngineObject |
| Dispose | Releases the reference to the native Carmenta Engine kernel instance the EngineObject represents. Inherited from EngineObject |
| Equals | Determines whether this instance is equal to another. Inherited from EngineObject |
| FindChildObject | Overloaded. Finds the child object with the specified name. Inherited from Operator |
| FlushCache | Marks the layer as flushed which will release cached resources during the next update. Inherited from Operator |
| GetChildObjects | Overloaded. Gets the child objects of the current object. Inherited from Operator |
| GetFeatures | Overloaded. Gets features from the operator chain. Inherited from Operator |
| GetLocalizedDescription | Gets a localized version of the operator description in a specific language. Inherited from Operator |
| GetLocalizedDisplayName | Gets a localized version of the operator display name in a specific language. Inherited from Operator |
| GetLocalizedIsoMetadataDocument | Gets the path to an ISO 19139 metadata document for a specific language. Inherited from Operator |
| GetRasterFeature | Overloaded. Gets raster features from the operator chain and merges them into a single raster. Inherited from Operator |
| HasLocalizedDescription | Checks if a localized version of the operator description is available in a specific language. Inherited from Operator |
| HasLocalizedDisplayName | Checks if a localized version of the operator display name is available in a specific language. Inherited from Operator |
| HasLocalizedIsoMetadataDocument | Checks if an ISO 19139 metadata document is available for a specific language. Inherited from Operator |
| SetLocalizedDescription | Sets a operator description in a specific language. Inherited from Operator |
| SetLocalizedDisplayName | Sets a operator display name in a specific language. Inherited from Operator |
| SetLocalizedIsoMetadataDocument | Sets the path to an ISO 19139 metadata document for the operator, for a specific language. Inherited from Operator |