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VR-Forces: Signature Sensor Model Overview

VR-Forces: Signature Sensor Model Overview

Note: This is current as of VRF 5.1.1 and 5.2.

VR-Forces CGF entities use a sensor model known as “Signature Sensor” to determine what other entities they can detect, and how much information they know about the entities they spot. This page is an overview of how this system works.

There are three parts to the sensor system, all of which can be configured:

  • The Target is the object being checked for detection. The target calculates an absolute signature that is passed to the propagator.

  • The Propagator that determines the impact of the environment between the spotter and the target on the detection. This converts the absolute signature from the target into an apparent signature that is passed to the sensor.

  • The Sensor component attached to the entity doing the sensing (referred to as Spotter), which uses an apparent signature to determine the detection level for the target.

Sensor Domains

Sensor domains represent different types of sensors, such as visual, infrared, and radar. VR-Forces uses the same sensor model for different domains, but with different parameters. Any time signature values, modifiers, propagators, or sensors are configured, they are configured per domain.

Signatures

The core concept of the sensor model is signatures. Signatures are similar in concept to radar cross-sections but are used across all domains.

There are two types of signatures used in the sensor mode:

  • Absolute Signature is a per-domain value that represents how visible a particular entity type is in that domain, independent of any viewing conditions. This is analogous to a radar cross-section. For example, a truck has a higher visual signature than a human.

  • Apparent Signature is an absolute signature modified for some specific viewing conditions. The calculation of an apparent signature requires an absolute signature as well as the location of the viewer and the target.

Target

The target object generates an absolute signature. Static signature values are configured for each entity type in the Simulation Object Editor. Additionally, signature modifiers can be configured for each object, which can cause the absolute signature to be dynamic depending on conditions. Examples of signature modifiers include:

  • speed modifier: Changes signature based on the speed of the entity, commonly used to lower the signature of stationary entities.

  • environment modifier: Changes the signature based on the day/night lighting cycle to make signatures lower in low light conditions.

  • emitter modifier: Increases the signature when the entity has active electromagnetic emissions to make radars more visible in radar domains when active.

Additional signature modifiers can be added through the C++ plug-in API for factors that are not already included in signature modifiers included with VR-Forces.

Note: In the case of remote entities, either from another VR-Forces Simulation Engine or from a non-VRF source, the absolute signatures are calculated by the simulation engine running the sensor in question, so it is important to have signatures configured in the SMS for entity types even if VR-Forces is not simulating those objects. The absolute signature values are not shared over the network between applications.

Propagator

The signature propagators are the part of the model that modify an absolute signature into an apparent signature. This is done using the location of both the target and the spotter object, as well as other simulation state that may interfere with the detection.

Propagators are configured per-domain as part of the physical world parameters.

Propagators typically take into account:

  • Terrain: Check to see if there is terrain between the target and spotter.

  • Other objects: Check whether other entities block the target and spotter.

  • Distance: The apparent signature typically decreases as distance increases between spotter and target.

  • Smoke / Visibility: Tactical smoke or low-visibility weather may block the sensor depending on the domain.

Additional custom propagators can be added through the C++ plug-in API.

Sensor

The sensor is a component configured on an entity that calls into the propagator for each potential target. The sensor receives the apparent signature, and uses that to determine how much (if anything) it knows about the target. The sensor has a sensitivity value that is applied as a scale factor to the incoming apparent signature.

The sensor typically uses a Detection Table that maps apparent signature to Combat Identification Levels (CID). The table provides a CID Level based on a particular target being at a particular apparent signature for a minimum amount of time. This is typically configured so that the longer a target is detected, the higher the CID level goes, thereby representing more information about a target being known the longer it is examined. If a target is lost and then spotted again by the sensor, it will start over from 0 time seen. Note that the contact fusion controller, which takes the output of sensors, can be configured to have memory of past contacts, but this is outside the sensor system itself.

Configuration

Details on configuring each of these parts of the sensor model is in the VR-Forces User’s Guide in the Configuring Sensors section (in the Using CameraFX Sensor Views chapter).