Navigation3D motion models and path following

Pathfinding only produces a geometric path. This chapter turns it into a flyable trajectory (post-processors) and into per-frame motion (FlightPathFollowComponent).

A path is not motion: the follow component publishes desired velocity and never writes Transform. To feed desired velocity into flight control, see Flight.

Post-processor overview

Post-processors convert a geometric path into a FlightTrajectory with speed hints and validate with CapsuleFree.

Type	Motion model	Can fail
`Hover`	Omnidirectional (multirotor / hover)	No (always succeeds)
`FixedWing`	Fixed wing (Dubins Airplane)	Yes (failed segments tabu-replan)

Failed segments feed pathfinding replan (bounded retries); persistent failure falls back to a straight trajectory.

Hover

Three stages: line-of-sight shortcut → centripetal Catmull-Rom smoothing (optional curvature tightening) → curvature-based speed labels with arrival slowdown ramps.

Relevant FlightAgentConfig: MaxSpeed, MaxAccel, SampleStep, ArrivalSlowdownDistance, MinSpeed, ExtraRadius.

FixedWing

Dubins Airplane: horizontal CSC/CCC shortest paths (MinTurnRadius); vertical linear height interpolation with loiter helices when too steep; G1 continuity at waypoints; per-segment CapsuleFree, failures become tabu.

Extras: MaxClimbAngle (default 0.5 rad), MinAirspeed (default 2.0). Pathfinding-stage turn penalties come from component FixedWingTurnAngleThreshold / FixedWingTurnPenalty (or query config).

Climb trajectories

Separate domain—not SVO flight post-process. FindClimbTrajectoryBetweenPositions(D) returns ClimbTrajectory:

Surface geodesic approximation resampled by arc length;
Each point carries m_normal (wall-facing), m_tangent, m_speedHint.

ClimbAgentConfig defaults: MaxSpeed 3.0, MaxAccel 6.0, SampleStep 0.5, ProjectMaxDistance 3.0.

FlightPathFollowComponent

Turns a trajectory into a per-frame desired velocity for your motion / physics layer to apply.

Typical usage

Navigation3D::FlightPathFollowRequestBus::Event(
 agentEntityId, &Navigation3D::FlightPathFollowRequests::StartFollowing, trajectory);

// Each frame:
AZ::Vector3 v;
Navigation3D::FlightPathFollowRequestBus::EventResult(
 v, agentEntityId, &Navigation3D::FlightPathFollowRequests::GetDesiredVelocity);
// Apply v in your motion layer

Also: StartFollowingOnVolume, Stop, IsFollowing, GetPreferredVelocity (pre-avoidance intent), GetDesiredOrientation.

FlightFollowConfig

Field	Default	Purpose
`m_lookaheadBase`	`2.0`	Pure-pursuit base lookahead (m)
`m_lookaheadSpeedFactor`	`0.5`	Lookahead grows with speed
`m_arrivalTolerance`	`1.0`	Arrival distance (m)
`m_arrivalSpeedThreshold`	`0.5`	Arrival speed threshold (m/s)
`m_deviationThreshold`	`3.0`	Fires `OnPathDeviated` (m)
`m_maxSpeed`	`10.0`	Speed cap
`m_headingMode`	`VelocityDirection`	Heading mode
`m_lookaheadSafetyCheck`	`true`	CapsuleFree lookahead against SVO
`m_fixedWing`	`false`	Fixed-wing follow (no hover / reverse)
`m_minAirspeed`	`2.0`	Fixed-wing min airspeed
`m_avoidance`	see below	Velocity-obstacle avoidance

FlightHeadingMode: VelocityDirection / TowardTarget / Free (external control).

Velocity obstacles (VelocityObstacleConfig)

Field	Default	Purpose
`m_enabled`	`true`	Enable avoidance
`m_queryRadius`	`10.0`	Nearby dynamic-body query radius (m)
`m_timeHorizon`	`2.0`	Time horizon (s)
`m_queryIntervalTicks`	`2`	Re-query obstacles every N ticks
`m_sampleDirections`	`24`	Candidate velocity directions
`m_reciprocal`	`false`	Reciprocal avoidance (ORCA-style)

Global switch: /O3DE/Gems/Navigation3D/Runtime/VelocityObstacleEnabled (default true).

Lifecycle notifications

FlightPathFollowNotificationBus: OnDesiredVelocityUpdated / OnPathCompleted / OnPathDeviated / OnPathBlocked / OnAvoidanceFailed (scriptable).

Hook into your motion layer

Query → FlightTrajectory
 → FlightPathFollow.StartFollowing
 → each frame GetDesiredVelocity → your motion / physics → Transform
 → deviate / blocked → your logic re-queries

Follow only answers “where / how fast”; not “how to move”.
Listen for OnPathDeviated / OnPathBlocked to decide when to replan.

Next steps

HTN integration — let a planner drive takeoff / flight
Debugging — paths / velocity missing or wrong