PlotLayer Class
A layer optimized for efficient rendering of large numbers of simple point objects.
NuGet/Assembly: Carmenta.Engine.5.16.2.nupkg (in the CECore assembly)
Syntax
public class PlotLayer : LayerRemarks
A PlotLayer is a layer type that is highly optimized for rendering large numbers of simple point objects in a 2D view or a 3D globe view, for instance radar plots. The point objects, or plots, are extremely light-weight, they consist only of a coordinate pair or triplet. Because of this, the simple visualization and efficient use of graphics hardware, a PlotLayer can typically handle one or two orders of magnitude more objects than the usual solution with individual point features in a MemoryDataSet in an OrdinaryLayer.
Visualization of plots is specified using the PlotSymbol class. It is basically either a simple square or a RasterSymbol.
Plots are added to the layer in batches, with the AddPlots or AddPlots3D methods. Each batch consists of an array of coordinate pairs or triplets (the geographic position of the plots), and the corresponding visualization. All plots in a batch have the same visualization. Rendering will be more efficient with large but few batches, compared to many small.
Individual batches can also be updated with UpdatePlots or UpdatePlots3D, or removed with RemovePlots. When updating a batch, you can replace both the coordinate array and the visualization, or keep the existing plots and just change the visualization. Changing the visualization is cheap, so it possible to implement efficient "animations" of the plots, for example fading them out after some delay.
Even though the plots are not real Feature instances, they can still be picked and selected. View.WhatsIn will return presentation objects for both regular features and plots, and the selection mechanism in the view can handle both types of selected objects. The StandardTool and StandardTool3D classes are aware of plots, and can change the mouse cursor and select and deselect both features and plots.
Selection visualization is not supported automatically though. But using the View.SelectionChanged event, it is possible to create temporary features for selected plots and insert them into MemoryDataSet, using the full visualization capabilities for features.
One issue with plot selection is the way individual plots are identified. The PlotId class used as a plot identifier contains the identity of the PlotLayer and the batch the plot belongs to, plus its index in the batch. This means that selection will only work well if the batches are not changed; if the application updates a batch and adds or removes plots, the selection mechanism will not be useful.
PlotLayer is supported in both 2D and 3D views. It can not be a child layer of other buffering layers, like TileLayer, BitmapLayer or LabelOrganizingLayer. In addition, the PlotLayer class can not be used with the Printer class.
When a PlotLayer is used with an OpenGL drawable, OpenGL version 1.5 or later is required to render plots with raster symbols. If the OpenGL version is lower than 1.5, typically when running an application over a Remote Desktop connection, the raster symbols will be rendered as colored squares. These limitations do not apply to the DirectX renderer.
Inheritance Hierarchy
System.Object (not available in C#)
EngineObject
Layer
PlotLayer
Platforms
Windows, Linux, Android
PlotLayer Members
The PlotLayer type has the following members.
Constructors
| Name | Description |
|---|---|
| PlotLayer | Initializes a new instance of the PlotLayer class. |
Properties
| Name | Description |
|---|---|
| BlendMode | Gets or sets the blend mode that determines how the layer is combined with previously rendered layers. Inherited from Layer |
| Condition | Gets or sets the Condition that determines whether the PlotLayer is drawn or not. Inherited from Layer |
| CoverageHint | Gets or sets a value that can assert that the visualization is fully opaque within the data extent. Inherited from Layer |
| Description | Gets or sets a short description of the layer. Inherited from Layer |
| DisableOnError | Gets or sets a value specifying if an error within the layer should automatically disable the layer, or throw an exception. Inherited from Layer |
| DisplayName | Gets or sets a display name for the layer. Inherited from Layer |
| Effects | List of effects Inherited from Layer |
| Enabled | Determines whether the PlotLayer is enabled or not. Inherited from Layer |
| EnabledDuringQuickUpdates | Determines whether the PlotLayer is temporarily turned off during mouse interactions. Inherited from Layer |
| HoveredPlotSymbol | Gets or sets the symbol used for a hovered plot. |
| Id | Gets a unique id of this PlotLayer instance. |
| IsDisposed | Gets a value that tells whether the current PlotLayer has been disposed. Inherited from EngineObject |
| IsoMetadataDocument | Gets or sets the path or URL to an ISO 19139 metadata document for the layer. Inherited from Layer |
| Legend | Gets or sets a map legend associated with this layer. Inherited from Layer |
| LengthUnit | Gets or sets the length unit used to determine the size of the plots. |
| MaxScale | Gets or sets the highest inverted nominal scale in a 2D view, or the furthest distance in a 3D globe view, at which objects from this PlotLayer should be drawn. Inherited from Layer |
| MinScale | Gets or sets the lowest inverted nominal scale this PlotLayer should be drawn at. Inherited from Layer |
| Name | Gets or sets the name of the layer. Inherited from Layer |
| NamedStyles | Gets the list of named styles that can be enabled for the layer. Inherited from Layer |
| NativeHandle | Gets the native Carmenta Engine kernel object the current PlotLayer represents. Inherited from EngineObject |
| Opacity | Gets or sets a value that specifies the opacity of the layer. Inherited from Layer |
| Selectable | Gets or sets a value that determines whether features in this PlotLayer can be selected. Inherited from Layer |
| SelectedPlotSymbol | Gets or sets the symbol used for selected plots. |
| IUserProperties.UserProperties | Gets the AttributeSet that contains the user properties. Inherited from IUserProperties |
Methods
| Name | Description |
|---|---|
| AddPlots | Adds a new batch of plots to the PlotLayer. |
| AddPlots3D | Adds a new batch of plots to the PlotLayer. |
| 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 |
| EnableStyle | Enables or disables a named style for the layer. Inherited from Layer |
| Equals | Determines whether this instance is equal to another. Inherited from EngineObject |
| FindChildObject | Overloaded. Finds the child object with the specified name. Inherited from Layer |
| FlushCache | Marks the layer as flushed which will release cached resources during the next update. Inherited from Layer |
| GetChildObjects | Overloaded. Gets the child objects of the current object. Inherited from Layer |
| GetDataBounds | Calculates the bounds of all dataset coverages in the layer. Inherited from Layer |
| GetFeatureAttributes | Gets information about all attributes that may be present on features in this layer. Inherited from Layer |
| GetFeatures | Overloaded. Gets features from the layer and any child layers. Inherited from Layer |
| GetLastError | Gets the error message for the last error that occurred within the layer. Inherited from Layer |
| GetLocalizedDescription | Gets a localized version of the layer description in a specific language. Inherited from Layer |
| GetLocalizedDisplayName | Gets a localized version of the layer display name in a specific language. Inherited from Layer |
| GetLocalizedIsoMetadataDocument | Gets the path to an ISO 19139 metadata document for a specific language. Inherited from Layer |
 GetPlotLayerById | Locates a PlotLayer instance given its layer identity. |
| HasLocalizedDescription | Checks if a localized version of the layer description is available in a specific language. Inherited from Layer |
| HasLocalizedDisplayName | Checks if a localized version of the layer display name is available in a specific language. Inherited from Layer |
| HasLocalizedIsoMetadataDocument | Checks if an ISO 19139 metadata document is available for a specific language. Inherited from Layer |
| IsStyleEnabled | Checks if a certain style is enabled for the layer or not. Inherited from Layer |
| RemoveAllPlots | Removes all plot batches from this PlotLayer. |
| RemovePlots | Removes an existing plot batch from this PlotLayer. |
| SetLocalizedDescription | Sets a layer description in a specific language. Inherited from Layer |
| SetLocalizedDisplayName | Sets a layer display name in a specific language. Inherited from Layer |
| SetLocalizedIsoMetadataDocument | Sets the path to an ISO 19139 metadata document for the layer, for a specific language. Inherited from Layer |
| UpdatePlots | Updates the plots and/or visualization of an existing plot batch. |
| UpdatePlots3D | Updates the plots and/or visualization of an existing plot batch. |
Events
| Name | Description |
|---|---|
| EnabledChanged | Occurs when the value of the Enabled property has changed. Inherited from Layer |