Table Of Contents
Table Of Contents

Visualizing Terrain and Urban Environment

Goals

It is often desirable for simulations to have a real world context. One way to achieve this is to place network nodes on a real world map. The map doesn’t have any effect on the simulation, it only alters the visuals of the network. However, objects can be added to represent buildings, which can affect the simulation as obstacles to signal propagation.

This showcase is about placing a map in the simulation. It contains three example configurations of increasing complexity, each demonstrating various features of the visualization.

INET version: 4.0
Source files location: inet/showcases/visualizer/earth

About the Visualizer

The map can be displayed by including a SceneOsgEarthVisualizer module in the network. It can display the map in the 3D view by using osgEarth, thus any part of the world can be inserted (provided there is a source for the map data). The use of the map requires an Internet connection, and it is only available in the 3D view.

Visualization with the Default Settings

This example configuration demonstrates inserting the map of downtown Boston into the simulation. It can be run by choosing the DefaultSettings configuration from the ini file. It uses the following network:

../../../../_images/defaultnetwork.png

The network contains an IntegratedVisualizer module, and an OsgGeographicCoordinateSystem module. The configuration from omnetpp.ini is the following:

*.visualizer.osgVisualizer.sceneVisualizer.typename = "SceneOsgEarthVisualizer"
*.visualizer.osgVisualizer.sceneVisualizer.mapFile = "boston.earth"

# Coordinates of the scene origin on the map
*.coordinateSystem.sceneLongitude = -71.06792deg
*.coordinateSystem.sceneLatitude = 42.35717deg

By default, the type of the scene visualizer module in IntegratedVisualizer is SceneOsgVisualizer. Inserting the map requires the SceneOsgEarthVisualizer module, thus, the default OSG scene visualizer is replaced. The SceneOsgEarthVisualizer provides the same functionality as SceneOsgVisualizer, and adds support for the osgEarth map.

To display the map, the visualizer requires a .earth file. This is an XML file that specifies how the source data is turned into a map, and how to fetch the necessary data from the Internet. In this configuration, we use the boston.earth file that contains OpenStreetMap configured as map data source. More .earth files can be found at osgearth.org, and there are also instructions there on how to create .earth files.

Locations on the map are identified with geographical coordinates, i.e. longitude and latitude. In INET, locations of nodes and objects are represented internally by Cartesian coordinates relative to the simulation scene’s origin, and the OsgGeographicCoordinateSystem module is responsible for converting between geographical and Cartesian coordinates. In order to define the mapping between the two, the geographical coordinates of the simulation scene’s origin must be specified in the coordinate system module’s sceneLongitude and sceneLatitude parameters. In our configuration, the scene’s origin is set to somewhere near a large park in Boston. Additionally, the origin’s altitude could also be configured (sceneAltitude); however, specifying the latitude and longitude is sufficient for the map visualization to work. The scene’s orientation can also be specified in the coordinate system module’s parameters using Euler angles (sceneHeading, sceneElevation, sceneBank). In the default setting, the X axis points East, the Y axis points North, and the Z axis points up.

The size of the simulation scene is determined automatically, taking into account the position of objects, network nodes, and movement constraints of network nodes. Thus, everything in the simulation should happen within the boundaries of the simulation scene. The scene floor is visualized on the map using a semi-transparent rectangle overlay. (Displaying the scene floor is optional, but turned on by default.) When the simulation starts, the view will be centered on the Cartesian coordinate system’s origin if there are no nodes in the network. If there are nodes, the initial viewpoint will be set so that all nodes are visible.

The scene’s 3D view should look like the following when the simulation is run. The map is displayed on the 3D scene. Since there are no nodes or objects in the network, the size of the scene is zero and the screen floor is not visible.

../../../../_images/defaultmap.png

Adding Physical Objects

The map doesn’t affect simulations in any way, just gives a real world context to them. For network nodes to interact with their environment, physical objects have to be added. The example configuration for this section can be run by selecting the PhysicalObjects configuration from the ini file. It extends the previous configuration by adding physical objects, meant to represent blocks of buildings, to the simulation. The objects could affect radio transmissions if an obstacle loss model was set.

The network for this configuration extends the network from the previous section with a PhysicalEnvironment module:

../../../../_images/objectsnetwork.png

The configuration for this example simulation extends the previous configuration with the following:

*.physicalEnvironment.coordinateSystemModule = "coordinateSystem"
*.physicalEnvironment.config = xmldoc("obstacle.xml")

The PhysicalEnvironment module is responsible for placing the physical objects on the scene. The physical environment module doesn’t use a coordinate system module by default, but it is configured to use the one present in the network. This makes it possible to define the objects using geographical coordinates. The objects are defined in the obstacle.xml config file.

The scene looks like the following when the simulation is run. The objects that represent blocks of buildings are displayed as semi-transparent red blocks, and the group of trees at the park’s edge is displayed as a semi-transparent green block.

../../../../_images/objectsmap.png

Placing Network Nodes on the Map

This example configuration demonstrates the placement of network nodes on the map. The simulation can be run by choosing the NetworkNodes configuration from the ini file. The network for this configuration extends the previous network with a radio medium and a network configurator module. It also adds four AdhocHost’s:

../../../../_images/nodesnetwork.png

The configuration extends the previous configuration with the following:

*.visualizer.osgVisualizer.sceneVisualizer.sceneShading = false
*.visualizer.osgVisualizer.sceneVisualizer.sceneColor = "#000000"
*.visualizer.osgVisualizer.sceneVisualizer.sceneOpacity = 0.1

# Coordinate system settings
*.coordinateSystem.sceneAltitude = 1m
*.coordinateSystem.sceneHeading = 68.3deg

# Mobility settings
*.host*.mobility.typename = "StationaryMobility"
*.host*.mobility.coordinateSystemModule = "coordinateSystem"
*.host*.mobility.initialAltitude = 1m
*.host*.mobility.initFromDisplayString = false

# Node position settings
*.host1.mobility.initialLatitude = 42.35659deg
*.host1.mobility.initialLongitude = -71.06762deg

*.host2.mobility.initialLatitude = 42.35585deg
*.host2.mobility.initialLongitude = -71.06727deg

*.host3.mobility.initialLatitude = 42.35716deg
*.host3.mobility.initialLongitude = -71.06911deg

*.host4.mobility.initialLatitude = 42.35685deg
*.host4.mobility.initialLongitude = -71.06639deg

The first block of lines configures the scene to be semi-transparent black, so that the underlying map is visible. The next block sets the altitude of the scene. By default, the altitude is zero; we set it to one meter, so that the nodes are not on the level of the ground. The heading is also specified, so that the edges of the scene roughly align with the streets on the map.

The rest of the configuration deals with placing the network nodes on the map. The mobility type of nodes is set to StationaryMobility, which is a mobility module that has parameters for positioning using geographical coordinates. The required latitude and longitude values can be obtained from www.openstreetmap.org. Once on that site, choose Share from the menu at the right, and tick Include marker. The marker can be dragged on the map, and the coordinates of the marker’s location can be read (and copy-pasted into the ini file) from the Share panel.

../../../../_images/openstreetmap.png

The scene with the nodes looks like the following when the simulation is run. The scene floor is visible against the map, and you can verify that the nodes have been placed at the specified coordinates.

../../../../_images/nodesmap2.png

Sources: omnetpp.ini, EarthVisualizationShowcase.ned

Further Information

For further information about the visualizer, refer to the NED documentation of SceneOsgEarthVisualizer and OsgGeographicCoordinateSystem.

Discussion

Use this page in the GitHub issue tracker for commenting on this showcase.