Class TrafficBehaviour

Namespace: mobisim.Traffic

Abstract MonoBehaviour that translates sensor collision events into active TrafficProcess instances, driving autonomous actor behaviour such as gap-keeping, stopline compliance, and pedestrian avoidance.

public class TrafficBehaviour : MonoBehaviour

Inheritance

object→Object→Component→Behaviour→MonoBehaviour→TrafficBehaviour

Derived

• PedestrianTrafficBehavior
• VehicleTrafficBehavior

Remarks

Traffic actors must respond to dynamic obstacles (other vehicles, pedestrians, stoplines) without a global path-planner. TrafficBehaviour achieves this reactively: when a sensor fires its OnDetected event, Collider) creates a new TrafficProcess configured with keep/stop distances and adds it to the active list. Each process drives the actor's speed independently of the movement command system, so braking and path-following coexist.

The IsHijacked / Object) mechanism lets AIBrainComponent take over the update cycle when the Behaviour Tree is running. Update is suppressed; the BT calls DoUpdate explicitly each tick, giving it precise control over when traffic processes are evaluated relative to movement commands.

Concrete subclasses (VehicleTrafficBehavior, PedestrianTrafficBehavior) override ContactStruct@) to map detected layer masks to the correct process type without the base class knowing about vehicle physics or pedestrian rigs.

Fields

keepDistanceOtherCarsAreaSensors

Narrower forward-facing sensors for gap-keeping behind other vehicles. Multiple sensors cover lane-change scenarios where the lead vehicle drifts laterally.

[Space(10)]
[Tooltip("Sensors used to maintain distance from other cars.")]
[SerializeField]
protected Optional<Sensor[]> keepDistanceOtherCarsAreaSensors

Field Value

Optional<Sensor[]>

searchAreaSensor

Wide-area sensor that sweeps for all traffic objects (vehicles, pedestrians, stoplines).

[Header("Sensors References")]
[Tooltip("Sensor responsible for detecting traffic in the surrounding area.")]
[SerializeField]
protected Optional<Sensor> searchAreaSensor

Field Value

Optional<Sensor>

stoplineContactParameter

Distance thresholds and dwell time applied when stopping at a stopline detected by searchAreaSensor.

[Tooltip("Contact parameters for handling stoplines, including stop duration.")]
[SerializeField]
protected TrafficBehaviour.StoplineContactStruct stoplineContactParameter

Field Value

TrafficBehaviour.StoplineContactStruct

trafficObjectContactParameter

Distance thresholds applied when reacting to objects detected by the wide-area searchAreaSensor that are not stoplines.

[Space(10)]
[Tooltip("Contact parameters for handling general traffic object interactions.")]
[SerializeField]
protected TrafficBehaviour.ContactStruct trafficObjectContactParameter

Field Value

TrafficBehaviour.ContactStruct

Properties

CanProcessTraffic

true when this component is enabled and has at least one active process to run. Used by the BT to determine whether to call DoUpdate this tick.

public bool CanProcessTraffic { get; }

Property Value

bool

IsHijacked

true when an external controller (e.g., AIBrainComponent) is driving this actor's update cycle, suppressing Update so the BT can call DoUpdate at its own cadence.

public bool IsHijacked { get; }

Property Value

bool

KeepDistanceSensors

Active gap-keeping sensors, or null if none are assigned in the Inspector.

public Sensor[] KeepDistanceSensors { get; }

Property Value

Sensor[]

Processes

Read-only view of the active process list for external inspection or debugging.

public List<TrafficProcess> Processes { get; }

Property Value

List<TrafficProcess>

Methods

CheckCanAddedProcess(TrafficProcess)

Validates that process can be added without violating its declared ProcessConstraint.

protected bool CheckCanAddedProcess(TrafficProcess process)

Parameters

Name	Type	Description
process	TrafficProcess	Candidate process to validate.

Returns

bool — true if the process may be added; false if the constraint rejects it.

Remarks

Prevents duplicate gap-keeping processes from stacking when the same vehicle is detected by overlapping sensors simultaneously, which would cause the actor to over-brake.

DoUpdate()

Advances all active processes by one tick and removes any that have completed.

public virtual void DoUpdate()

Remarks

Marked virtual and public so the BT (AIBrainComponent) can call it explicitly when IsHijacked suppresses the Unity Update loop.

OnDestroy()

Unsubscribes from sensor events to prevent callbacks on a destroyed component.

protected void OnDestroy()

OnKeepDistanceSensorDetected(Collider)

Creates and starts the appropriate TrafficProcess when a gap-keeping sensor detects another object, subject to the constraint check.

protected virtual void OnKeepDistanceSensorDetected(Collider other)

Parameters

Name	Type	Description
other	Collider	The detected collider from the gap-keeping sensor.

OnSearchAreaSensorDetected(Collider)

Reserved callback for the wide-area search sensor; not yet implemented in the base class. Subclasses may override this to react to objects entering the search area.

protected void OnSearchAreaSensorDetected(Collider other)

Parameters

Name	Type	Description
other	Collider	The detected collider.

SetController(Object)

Registers controller as the external driver of this actor's update cycle, setting IsHijacked to true.

public void SetController(Object controller)

Parameters

Name	Type	Description
controller	Object	The BT component (or other controller) taking over updates.

Start()

Initialises the process list and subscribes to sensor collision events.

protected void Start()

TryGetProcess(GameObject, out TrafficProcess, out ProcessData, out ContactStruct)

Maps otherObject to the correct TrafficProcess subclass and populates its ProcessData, using the object's layer to distinguish vehicles from pedestrians.

protected virtual bool TryGetProcess(GameObject otherObject, out TrafficProcess process, out TrafficProcess.ProcessData processData, out TrafficBehaviour.ContactStruct currentContactValueParameter)

Parameters

Name	Type	Description
otherObject	GameObject	The detected object.
process	TrafficProcess	Receives the newly created process instance.
processData	TrafficProcess.ProcessData	Receives the process initialisation data.
currentContactValueParameter	TrafficBehaviour.ContactStruct	Receives the contact thresholds for this interaction.

Returns

bool — true if a process was created; false if the object should be ignored.

Remarks

The base implementation differentiates on the "Mine" layer (pedestrians/player) versus all other layers (vehicles). Subclasses override this to add vehicle-type-specific logic (e.g., checking relative speed before spawning a braking process).