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Using the Camera System

This document explains how to move, rotate, and control cameras using the APIs in CameraSystem.swift.

Get the Game Camera

For gameplay, always use the game camera (not the editor/scene camera). Call findGameCamera() and make it active:

let camera = findGameCamera()
setCamera(.active(camera))

If no game camera exists, findGameCamera() creates one and sets it up with default values.

Configure global projection defaults at startup:

setCamera(.defaultFOV(70.0))
setCamera(.clipPlanes(near: 0.1, far: 1000.0))

Translate (Move) the Camera

Use absolute or relative movement:

// Absolute position
moveCameraTo(entityId: camera, 0.0, 3.0, 7.0)

// Relative movement in camera local space
cameraMoveBy(entityId: camera, delta: simd_float3(0.0, 0.0, -1.0), space: .local)

// Relative movement in world space
cameraMoveBy(entityId: camera, delta: simd_float3(1.0, 0.0, 0.0), space: .world)

Rotate the Camera

Use rotateCamera for pitch/yaw rotation, or cameraLookAt to aim at a target.

// Rotate by pitch/yaw (radians), with optional sensitivity
rotateCamera(entityId: camera, pitch: 0.02, yaw: 0.01, sensitivity: 1.0)

// Look-at orientation
cameraLookAt(
    entityId: camera,
    eye: simd_float3(0.0, 3.0, 7.0),
    target: simd_float3(0.0, 0.0, 0.0),
    up: simd_float3(0.0, 1.0, 0.0)
)

Camera Follow

Follow a target entity with a fixed offset. You can optionally smooth the motion.

let target = findEntity(name: "player") ?? createEntity()
let offset = simd_float3(0.0, 2.0, 6.0)

// Instant follow
cameraFollow(entityId: camera, targetEntity: target, offset: offset)

// Smoothed follow
cameraFollow(entityId: camera, targetEntity: target, offset: offset, smoothFactor: 6.0, deltaTime: deltaTime)

Dead-Zone Follow

cameraFollowDeadZone only moves the camera when the target leaves a box around it. This is useful for platformers and shoulder cameras.

let deadZone = simd_float3(1.0, 0.5, 1.0)
cameraFollowDeadZone(
    entityId: camera,
    targetEntity: target,
    offset: offset,
    deadZoneExtents: deadZone,
    smoothFactor: 6.0,
    deltaTime: deltaTime
)

Camera Path Following

The camera path system moves the active camera through a sequence of waypoints with smooth interpolation.

Start a Path

let waypoints = [
    CameraWaypoint(
        position: simd_float3(0, 5, 10),
        rotation: simd_quatf(angle: 0, axis: simd_float3(0, 1, 0)),
        segmentDuration: 2.0
    ),
    CameraWaypoint(
        position: simd_float3(10, 5, 10),
        rotation: simd_quatf(angle: Float.pi / 4, axis: simd_float3(0, 1, 0)),
        segmentDuration: 2.0
    )
]

startCameraPath(waypoints: waypoints, mode: .once)

You can also build waypoints that look at a target:

let waypoint = CameraWaypoint(
    position: simd_float3(0, 5, 10),
    lookAt: simd_float3(0, 0, 0),
    up: simd_float3(0, 1, 0),
    segmentDuration: 2.0
)

Update Every Frame

Call updateCameraPath(deltaTime:) from your main update loop:

func update(deltaTime: Float) {
    updateCameraPath(deltaTime: deltaTime)
}

Looping and Completion

startCameraPath(waypoints: waypoints, mode: .loop)

let settings = CameraPathSettings(startImmediately: true) {
    print("Camera path completed")
}
startCameraPath(waypoints: waypoints, mode: .once, settings: settings)

Stopping and Querying Path State

stopCameraPath()

if isCameraPathActive() {
    // don't start a new path while one is already running
}

Orbit Camera

orbitCameraAround rotates the camera around cameraComponent.orbitTarget (set with setOrbitOffset), which is the pattern used by the shipped demos for mouse-drag orbit controls:

// Establish the pivot point in front of the camera
setOrbitOffset(entityId: camera, uTargetOffset: 5.0)

// Feed raw mouse-drag delta in
orbitCameraAround(entityId: camera, uDelta: dragDelta) // pre-scaled by -0.01 internally

To orbit around another entity at a fixed radius and angular speed instead of a mouse-driven pivot:

cameraOrbitTarget(
    entityId: camera,
    centerEntity: target,
    radius: 8.0,
    angularSpeed: 0.5, // radians/sec
    deltaTime: deltaTime,
    offsetY: 1.0
)

orbitAround(entityId:uPosition:) is the lower-level primitive both of the above build on, if you need direct control over the yaw/pitch delta.

WASD / Free-Look Movement

moveCameraWithInput drives free-fly movement from a WASD+QE-style input struct (ignored while InputSystem.shared.cameraControlMode == .orbiting):

moveCameraWithInput(
    entityId: camera,
    input: (w: keysDown.w, a: keysDown.a, s: keysDown.s, d: keysDown.d, q: keysDown.q, e: keysDown.e),
    speed: 5.0,
    deltaTime: deltaTime
)

Related low-level helpers: cameraLookAboutAxis(entityId:uDelta:) applies a mouse-look style yaw/pitch delta, and moveCameraAlongAxis(entityId:uDelta:) moves along the camera's local right/up/forward axes.

Local-Space Follow

cameraFollowLocal is like cameraFollow, but the offset is expressed in the target's local space rather than world space — useful when the target rotates and the camera should stay attached to a specific side (e.g. behind a turning vehicle):

cameraFollowLocal(
    entityId: camera,
    targetEntity: target,
    localOffset: simd_float3(0.0, 2.0, -6.0),
    smoothFactor: 6.0,
    deltaTime: deltaTime
)

Notes

  • startCameraPath and updateCameraPath operate on the active camera set with setCamera(.active(...)).
  • segmentDuration is the time to move from the current waypoint to the next.
  • For gameplay, always acquire the camera with findGameCamera() and set it active before path playback or follow logic.