State and Parameter Properties

Table of Contents

• Accessing State Properties
  • From the Sim Engine
  • From the GUI
  • From Remote Applications
• Supported Data Types for State and Parameter Properties

State and parameter properties are the easiest way to extend the state of VR-Forces simulation objects.

State and parameter properties can be defined in the OPE files and sysdef files of an SMS, adding new object state without the need for plug-in code. Both of the built-in EntityLevel and AggregateLevel models make heavy use of these properties.

VR-Forces users can add their own state properties and parameter properties without using the VR-Forces Toolkit. The VR-Forces Users Guide offers details on how state and parameter properties are defined in the section titled State Properties and Parameter Properties.

There are three types of properties:

• Parameter Properties
  • Static - This data cannot be changed at run-time.
  • External - This data is external and can be read by other VR-Forces entities. Can also be published to the network.
  • Double Buffered - As with all external data, this data is double buffered as part of the external state data. See External State.
  • Defined in the parameter-data section of the OPE or any sim component descriptor (such as in a sysdef file).
• External State Properties
  • Dynamic - This data is expected to change at run-time.
  • External - This data is external and can be read by other VR-Forces entities, as long as it is configured to be published to the network.
  • Double Buffered - As with all external data, this data is double buffered as part of the external state data. See External State.
  • Defined in the external-state-data (or just state-data) section of the OPE or any sim component descriptor (such as in a sysdef file).
• Internal State Properties
  • Dynamic - This data is expected to change at run-time.
  • Internal - This data is internal and cannot be read by other VR-Forces entities. Cannot be published to the network.
  • Better Performance - Since this data does not need to be shared with other entities, it can be stored in a way that offers better performance.
  • Defined in the internal-state-data section of the OPE or any sim component descriptor (such as in a sysdef file).

Accessing State Properties

From the Sim Engine

External state and parameter properties are stored in separate lists within the DtStatePropertiesStateComponent of all VR-Forces simulation objects. They can be most easily accessed using the DtVrfSimulatedSimObjectFacade.

Internal state properties are stored in the DtVrfObjectStateRepository of the DtLocalObject. They can only be accessed by the local entity and its components.

More details on how to access state properties from within sim engine plug-in code can be found on the following page:

Getting and Setting State Property Values

Please see the Add State Property (addStatePropertySim) example plug-in to see some sample code.

From the GUI

External state properties can be accessed from a DtGuiSimObject or DtSimObjectReference. Internal state properties are not published, and therefore are not accessible in the GUI. Please see the Add State Property (addStatePropertyGui) example plug-in to see some sample code for accessing the values of state properties for an entity.

More details on how to access state properties from within sim engine plug-in code can be found on the following page:

Getting and Setting State Property Values

From Remote Applications

Other applications that use VR-Link can access external state properties by instantiating special reflected lists that support them. These are DtReflectedVrfExtEntityList, DtReflectedVrfExtAggregateList, and DtReflectedVrfControlObjectList. The VRF Message Dump (vrfMsgDump) tool has a DtVrfStatePropertyPrinter that serves as an example of how to use these classes in your own remote application.

If you wish to access external state properties in other applications that are not using VR-Link, and therefore cannot use the extended reflected lists mentioned above, state properties can be published to HLA attributes or DIS Attribute PDU records. For more details on how state properties can be published, see the following page:

Internal state properties are not published, and therefore are not accessible in remote applications.

Publishing State Properties

Supported Data Types for State and Parameter Properties

The following table identifies the data types supported for state properties. The Data Type column indicates the name of the data type used in the C++ code. (The data types used in OPE files are slightly different.) The Description column describes the format of this type. The HLA Representation/Encoding column indicates what type should be used in an HLA 1516 FOM to match the specification in the OPE.

Data Types Supported for State Properties and Parameter Properties
Data Type	Description	HLA Representation/Encoding
DtRwInt, DtRwInt32	A 32-bit integer	RPRunsignedInteger32BE, HLAinteger32BE
DtRwInt16	A 16-bit integer	RPRunsignedInteger16BE, HLAinteger16BE
DtRwInt8	An 8-bit integer	RPRunsignedInteger8BE, HLAoctet
DtRwReal, DtRwReal64	A 64-bit float	HLAfloat64BE
DtRwReal32	A 32-bit float	HLAfloat32BE
DtRwBoolean	A Boolean	RPRboolean
DtRwString	An ASCII string	RPRnullTerminatedArray of HLAASCIIchar
DtRwVector	A location in geocentric coordinates	WorldLocationStruct, from the RPR FOM
C++: DtRwPropertiesFixedArray OPE:DtRwFixedArray	A fixed size list of items	HLAFixedArray
C++: DtRwPropertySizedString OPE: DtRwSizedString	An ASCII string (alternate encoding for DtRwString)	HLAASCIIstring
C++: DtRwPropertiesStructure OPE: DtRwStructure	A fixed structure with multiple named fields	HLAfixedRecord with matching fields
C++: DtRwPropertiesList OPE: DtRwList	A variable sized list of items	HLAvariableArray
C++: DtRwPropertiesMap OPE: DtRwMap	A variable sized map of items	HLAvariableArray of HLAfixedRecords, where the first field in each record is the key