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tera/src/aircraft/controller.ts
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TypeScript

/** Deterministic, renderer-independent fixed-wing flight over California. */
const EARTH_RADIUS_M = 6_371_000;
const TWO_PI = Math.PI * 2;
export type AircraftControlMode = "assisted" | "manual";
export type AircraftModeRequest = "none" | AircraftControlMode;
export interface AircraftGeographicPoint {
lat: number;
lng: number;
}
export interface AircraftWaypoint extends AircraftGeographicPoint {
id: string;
altitudeM: number;
}
export interface AircraftActionSnapshot {
throttle: number;
yaw: number;
pitch: number;
roll: number;
modeRequest: AircraftModeRequest;
reset: boolean;
}
export const NEUTRAL_AIRCRAFT_ACTIONS: Readonly<AircraftActionSnapshot> = Object.freeze({
throttle: 0,
yaw: 0,
pitch: 0,
roll: 0,
modeRequest: "none",
reset: false,
});
export interface CaliforniaFlightEnvelope {
minLat: number;
maxLat: number;
minLng: number;
maxLng: number;
minAltitudeM: number;
maxAltitudeM: number;
}
export const DEFAULT_CALIFORNIA_FLIGHT_ENVELOPE: Readonly<CaliforniaFlightEnvelope> =
Object.freeze({
minLat: 32.4,
maxLat: 42.1,
minLng: -124.6,
maxLng: -114.0,
minAltitudeM: 75,
maxAltitudeM: 6_000,
});
export interface AircraftControllerOptions {
initialPosition?: Partial<AircraftGeographicPoint>;
initialAltitudeM?: number;
initialHeadingDeg?: number;
initialSpeedMps?: number;
mode?: AircraftControlMode;
route?: readonly AircraftWaypoint[];
envelope?: CaliforniaFlightEnvelope;
minimumSpeedMps?: number;
maximumSpeedMps?: number;
assistedCruiseMps?: number;
assistedAltitudeM?: number;
/** Deterministic scenario wind, positive north/east in metres per second. */
windNorthMps?: number;
windEastMps?: number;
/** Deterministic sinusoidal gust amplitude. Zero disables turbulence. */
turbulenceMps?: number;
stallSpeedMps?: number;
batteryCapacityWh?: number;
/** Terrain/runway elevation callback used for ground contact and landing. */
terrainElevationM?: (lat: number, lng: number) => number;
fixedStepSeconds?: number;
maxFrameDeltaSeconds?: number;
}
export interface AircraftControllerState extends AircraftGeographicPoint {
altitudeM: number;
headingDeg: number;
pitchDeg: number;
rollDeg: number;
speedMps: number;
verticalSpeedMps: number;
mode: AircraftControlMode;
routeWaypointIndex: number;
routeWaypointId: string | null;
throttle: number;
yawInput: number;
pitchInput: number;
rollInput: number;
fanRadians: number;
angleOfAttackDeg: number;
liftCoefficient: number;
loadFactorG: number;
stalled: boolean;
windNorthMps: number;
windEastMps: number;
batteryWh: number;
energyUsedWh: number;
groundClearanceM: number;
onGround: boolean;
hardLanding: boolean;
envelopeContact: boolean;
elapsedSteps: number;
}
export interface AircraftControllerSnapshot extends AircraftControllerState {}
export interface TimedAircraftInputFrame {
steps: number;
actions?: Partial<AircraftActionSnapshot>;
}
export interface AircraftReplayResult {
trajectory: readonly AircraftControllerSnapshot[];
final: AircraftControllerSnapshot;
}
export interface AircraftCameraPose {
position: AircraftGeographicPoint & { altitudeM: number };
target: AircraftGeographicPoint & { altitudeM: number };
rollDeg: number;
}
interface ResolvedOptions {
initialPosition: AircraftGeographicPoint;
initialAltitudeM: number;
initialHeadingDeg: number;
initialSpeedMps: number;
mode: AircraftControlMode;
route: readonly AircraftWaypoint[];
envelope: CaliforniaFlightEnvelope;
minimumSpeedMps: number;
maximumSpeedMps: number;
assistedCruiseMps: number;
assistedAltitudeM: number;
windNorthMps: number;
windEastMps: number;
turbulenceMps: number;
stallSpeedMps: number;
batteryCapacityWh: number;
terrainElevationM: (lat: number, lng: number) => number;
fixedStepSeconds: number;
maxFrameDeltaSeconds: number;
}
function clamp(value: number, min: number, max: number): number {
return Math.max(min, Math.min(max, value));
}
function finiteOr(value: number | undefined, fallback: number): number {
return typeof value === "number" && Number.isFinite(value) ? value : fallback;
}
function moveToward(value: number, target: number, maximumDelta: number): number {
if (value < target) return Math.min(value + maximumDelta, target);
if (value > target) return Math.max(value - maximumDelta, target);
return value;
}
function wrapDegrees(value: number): number {
return ((value % 360) + 360) % 360;
}
function signedAngleDegrees(from: number, to: number): number {
return ((to - from + 540) % 360) - 180;
}
function distanceM(a: AircraftGeographicPoint, b: AircraftGeographicPoint): number {
const mean = ((a.lat + b.lat) / 2) * Math.PI / 180;
const north = (b.lat - a.lat) * Math.PI / 180 * EARTH_RADIUS_M;
const east = (b.lng - a.lng) * Math.PI / 180 * Math.cos(mean) * EARTH_RADIUS_M;
return Math.hypot(north, east);
}
function bearingDeg(a: AircraftGeographicPoint, b: AircraftGeographicPoint): number {
const mean = ((a.lat + b.lat) / 2) * Math.PI / 180;
return wrapDegrees(Math.atan2((b.lng - a.lng) * Math.cos(mean), b.lat - a.lat) * 180 / Math.PI);
}
function checkedEnvelope(value: CaliforniaFlightEnvelope | undefined): CaliforniaFlightEnvelope {
const envelope = { ...(value ?? DEFAULT_CALIFORNIA_FLIGHT_ENVELOPE) };
if (
!Number.isFinite(envelope.minLat) || !Number.isFinite(envelope.maxLat) ||
!Number.isFinite(envelope.minLng) || !Number.isFinite(envelope.maxLng) ||
!Number.isFinite(envelope.minAltitudeM) || !Number.isFinite(envelope.maxAltitudeM) ||
envelope.minLat >= envelope.maxLat || envelope.minLng >= envelope.maxLng ||
envelope.minAltitudeM >= envelope.maxAltitudeM
) throw new RangeError("aircraft flight envelope must be finite and ordered");
return envelope;
}
function checkedRoute(
route: readonly AircraftWaypoint[] | undefined,
envelope: CaliforniaFlightEnvelope,
): readonly AircraftWaypoint[] {
if (!route) return [];
const ids = new Set<string>();
return route.map((point) => {
if (
typeof point.id !== "string" || point.id.length === 0 || ids.has(point.id) ||
!Number.isFinite(point.lat) || !Number.isFinite(point.lng) ||
!Number.isFinite(point.altitudeM) ||
point.lat < envelope.minLat || point.lat > envelope.maxLat ||
point.lng < envelope.minLng || point.lng > envelope.maxLng ||
point.altitudeM < envelope.minAltitudeM || point.altitudeM > envelope.maxAltitudeM
) throw new RangeError(
"aircraft route waypoints must be finite, unique, and inside the flight envelope",
);
ids.add(point.id);
return { ...point };
});
}
function resolveOptions(value: AircraftControllerOptions): ResolvedOptions {
const envelope = checkedEnvelope(value.envelope);
const minimumSpeedMps = clamp(finiteOr(value.minimumSpeedMps, 20), 5, 100);
const maximumSpeedMps = clamp(finiteOr(value.maximumSpeedMps, 95), minimumSpeedMps, 250);
const assistedAltitudeM = clamp(
finiteOr(value.assistedAltitudeM, 1_500),
envelope.minAltitudeM,
envelope.maxAltitudeM,
);
const stallSpeedMps = clamp(
finiteOr(value.stallSpeedMps, Math.max(18, minimumSpeedMps + 3)),
minimumSpeedMps,
maximumSpeedMps * 0.8,
);
const terrainElevationM = value.terrainElevationM ?? (() => envelope.minAltitudeM);
if (typeof terrainElevationM !== "function") {
throw new RangeError("aircraft terrainElevationM must be a function");
}
return {
initialPosition: {
lat: clamp(finiteOr(value.initialPosition?.lat, 34.0522), envelope.minLat, envelope.maxLat),
lng: clamp(finiteOr(value.initialPosition?.lng, -118.2437), envelope.minLng, envelope.maxLng),
},
initialAltitudeM: clamp(finiteOr(value.initialAltitudeM, assistedAltitudeM), envelope.minAltitudeM, envelope.maxAltitudeM),
initialHeadingDeg: wrapDegrees(finiteOr(value.initialHeadingDeg, 320)),
initialSpeedMps: clamp(finiteOr(value.initialSpeedMps, 55), minimumSpeedMps, maximumSpeedMps),
mode: value.mode === "manual" ? "manual" : "assisted",
route: checkedRoute(value.route, envelope),
envelope,
minimumSpeedMps,
maximumSpeedMps,
assistedCruiseMps: clamp(finiteOr(value.assistedCruiseMps, 62), minimumSpeedMps, maximumSpeedMps),
assistedAltitudeM,
windNorthMps: clamp(finiteOr(value.windNorthMps, 0), -80, 80),
windEastMps: clamp(finiteOr(value.windEastMps, 0), -80, 80),
turbulenceMps: clamp(finiteOr(value.turbulenceMps, 0), 0, 30),
stallSpeedMps,
batteryCapacityWh: clamp(finiteOr(value.batteryCapacityWh, 54_000), 1_000, 500_000),
terrainElevationM,
fixedStepSeconds: clamp(finiteOr(value.fixedStepSeconds, 1 / 60), 1 / 240, 0.1),
maxFrameDeltaSeconds: clamp(finiteOr(value.maxFrameDeltaSeconds, 0.25), 0.05, 1),
};
}
export function normalizeAircraftActions(
value: Partial<AircraftActionSnapshot> | undefined,
): AircraftActionSnapshot {
return {
throttle: clamp(finiteOr(value?.throttle, 0), 0, 1),
yaw: clamp(finiteOr(value?.yaw, 0), -1, 1),
pitch: clamp(finiteOr(value?.pitch, 0), -1, 1),
roll: clamp(finiteOr(value?.roll, 0), -1, 1),
modeRequest: value?.modeRequest === "manual" || value?.modeRequest === "assisted"
? value.modeRequest
: "none",
reset: value?.reset === true,
};
}
function hasManualIntent(actions: AircraftActionSnapshot): boolean {
return (
actions.modeRequest === "manual" || actions.throttle > 0.02 ||
Math.abs(actions.yaw) > 0.06 || Math.abs(actions.pitch) > 0.06 || Math.abs(actions.roll) > 0.06
);
}
export class AircraftController {
private readonly options: ResolvedOptions;
private accumulator = 0;
private readonly current: AircraftControllerState;
constructor(options: AircraftControllerOptions = {}) {
this.options = resolveOptions(options);
this.current = {
...this.options.initialPosition,
altitudeM: this.options.initialAltitudeM,
headingDeg: this.options.initialHeadingDeg,
pitchDeg: 0,
rollDeg: 0,
speedMps: this.options.initialSpeedMps,
verticalSpeedMps: 0,
mode: this.options.mode,
routeWaypointIndex: 0,
routeWaypointId: null,
throttle: 0,
yawInput: 0,
pitchInput: 0,
rollInput: 0,
fanRadians: 0,
angleOfAttackDeg: 0,
liftCoefficient: 1,
loadFactorG: 1,
stalled: false,
windNorthMps: this.options.windNorthMps,
windEastMps: this.options.windEastMps,
batteryWh: this.options.batteryCapacityWh,
energyUsedWh: 0,
groundClearanceM: 0,
onGround: false,
hardLanding: false,
envelopeContact: false,
elapsedSteps: 0,
};
this.reset();
}
fixedStepSeconds(): number {
return this.options.fixedStepSeconds;
}
state(): Readonly<AircraftControllerState> {
return this.current;
}
snapshot(): AircraftControllerSnapshot {
return { ...this.current };
}
/** Restore a trusted JSON snapshot for deterministic environment checkpointing. */
restore(snapshot: AircraftControllerSnapshot): void {
const numeric = Object.entries(snapshot)
.filter(([, value]) => typeof value === "number")
.every(([, value]) => Number.isFinite(value));
const envelope = this.options.envelope;
if (
!numeric || (snapshot.mode !== "manual" && snapshot.mode !== "assisted") ||
snapshot.lat < envelope.minLat || snapshot.lat > envelope.maxLat ||
snapshot.lng < envelope.minLng || snapshot.lng > envelope.maxLng ||
snapshot.altitudeM < envelope.minAltitudeM || snapshot.altitudeM > envelope.maxAltitudeM ||
snapshot.speedMps < this.options.minimumSpeedMps ||
snapshot.speedMps > this.options.maximumSpeedMps ||
!Number.isSafeInteger(snapshot.elapsedSteps) || snapshot.elapsedSteps < 0
) throw new RangeError("aircraft snapshot is incompatible or invalid");
Object.assign(this.current, snapshot);
this.accumulator = 0;
}
reset(): void {
this.accumulator = 0;
Object.assign(this.current, this.options.initialPosition, {
altitudeM: this.options.initialAltitudeM,
headingDeg: this.options.initialHeadingDeg,
pitchDeg: 0,
rollDeg: 0,
speedMps: this.options.initialSpeedMps,
verticalSpeedMps: 0,
mode: this.options.mode,
routeWaypointIndex: 0,
routeWaypointId: this.options.route[0]?.id ?? null,
throttle: 0,
yawInput: 0,
pitchInput: 0,
rollInput: 0,
fanRadians: 0,
angleOfAttackDeg: 0,
liftCoefficient: 1,
loadFactorG: 1,
stalled: false,
windNorthMps: this.options.windNorthMps,
windEastMps: this.options.windEastMps,
batteryWh: this.options.batteryCapacityWh,
energyUsedWh: 0,
groundClearanceM: Math.max(0, this.options.initialAltitudeM - this.groundElevationM(
this.options.initialPosition.lat,
this.options.initialPosition.lng,
)),
onGround: false,
hardLanding: false,
envelopeContact: false,
elapsedSteps: 0,
});
}
private groundElevationM(lat: number, lng: number): number {
const value = this.options.terrainElevationM(lat, lng);
if (!Number.isFinite(value)) {
throw new RangeError("aircraft terrainElevationM must return a finite elevation");
}
return clamp(value, this.options.envelope.minAltitudeM, this.options.envelope.maxAltitudeM);
}
tick(deltaSeconds: number, actions: Partial<AircraftActionSnapshot> = NEUTRAL_AIRCRAFT_ACTIONS): number {
if (!Number.isFinite(deltaSeconds) || deltaSeconds <= 0) return 0;
const normalized = normalizeAircraftActions(actions);
if (normalized.reset) {
this.reset();
return 0;
}
this.accumulator += Math.min(deltaSeconds, this.options.maxFrameDeltaSeconds);
let steps = 0;
while (this.accumulator + Number.EPSILON >= this.options.fixedStepSeconds) {
this.stepNormalized(normalized);
this.accumulator -= this.options.fixedStepSeconds;
steps += 1;
}
return steps;
}
stepFixed(actions: Partial<AircraftActionSnapshot> = NEUTRAL_AIRCRAFT_ACTIONS): void {
const normalized = normalizeAircraftActions(actions);
if (normalized.reset) this.reset();
else this.stepNormalized(normalized);
}
private stepNormalized(actions: AircraftActionSnapshot): void {
const dt = this.options.fixedStepSeconds;
const manual = hasManualIntent(actions);
if (manual) this.current.mode = "manual";
else if (actions.modeRequest === "assisted") this.current.mode = "assisted";
let throttle = actions.throttle;
let yaw = actions.yaw;
let pitch = actions.pitch;
let roll = actions.roll;
if (this.current.mode === "assisted") {
throttle = clamp(0.5 + (this.options.assistedCruiseMps - this.current.speedMps) / 18, 0, 1);
const target = this.options.route[this.current.routeWaypointIndex];
if (target && distanceM(this.current, target) < 3_000 && this.options.route.length > 1) {
this.current.routeWaypointIndex = (this.current.routeWaypointIndex + 1) % this.options.route.length;
}
const waypoint = this.options.route[this.current.routeWaypointIndex];
this.current.routeWaypointId = waypoint?.id ?? null;
const desiredHeading = waypoint ? bearingDeg(this.current, waypoint) : this.options.initialHeadingDeg;
const headingError = signedAngleDegrees(this.current.headingDeg, desiredHeading);
roll = clamp(headingError / 38, -1, 1);
yaw = clamp(headingError / 90, -0.45, 0.45);
const altitudeTarget = waypoint?.altitudeM ?? this.options.assistedAltitudeM;
pitch = clamp((altitudeTarget - this.current.altitudeM) / 350, -0.65, 0.65);
}
this.current.throttle = moveToward(this.current.throttle, throttle, 0.8 * dt);
this.current.yawInput = moveToward(this.current.yawInput, yaw, 2.5 * dt);
this.current.pitchInput = moveToward(this.current.pitchInput, pitch, 2.2 * dt);
this.current.rollInput = moveToward(this.current.rollInput, roll, 2.8 * dt);
const gustPhase = this.current.elapsedSteps * dt * 0.73;
const gustNorth = Math.sin(gustPhase) * this.options.turbulenceMps;
const gustEast = Math.sin(gustPhase * 0.61 + 1.7) * this.options.turbulenceMps * 0.72;
this.current.windNorthMps = this.options.windNorthMps + gustNorth;
this.current.windEastMps = this.options.windEastMps + gustEast;
const targetRoll = this.current.rollInput * 58 + gustEast * 0.22;
const targetPitch = this.current.pitchInput * 22 + gustNorth * 0.08;
this.current.rollDeg = moveToward(this.current.rollDeg, targetRoll, 55 * dt);
this.current.pitchDeg = moveToward(this.current.pitchDeg, targetPitch, 28 * dt);
const flightPathDeg = Math.atan2(
this.current.verticalSpeedMps,
Math.max(1, this.current.speedMps),
) * 180 / Math.PI;
this.current.angleOfAttackDeg = this.current.pitchDeg - flightPathDeg;
this.current.liftCoefficient = clamp(1 + this.current.angleOfAttackDeg * 0.055, 0.05, 1.6);
this.current.stalled = this.current.speedMps < this.options.stallSpeedMps ||
Math.abs(this.current.angleOfAttackDeg) > 19;
const stallDrag = this.current.stalled ? 3.8 : 0;
const batteryFactor = clamp(this.current.batteryWh / Math.max(1, this.options.batteryCapacityWh * 0.08), 0, 1);
const thrust = this.current.throttle * 8.5 * batteryFactor;
const drag = 1.2 + this.current.speedMps * this.current.speedMps * 0.00075 + stallDrag;
this.current.speedMps = clamp(
this.current.speedMps + (thrust - drag) * dt,
this.options.minimumSpeedMps,
this.options.maximumSpeedMps,
);
const bankTurn = Math.sin(this.current.rollDeg * Math.PI / 180) * 24;
this.current.headingDeg = wrapDegrees(
this.current.headingDeg + (bankTurn + this.current.yawInput * 20) * dt,
);
const liftAuthority = clamp(
this.current.liftCoefficient * (this.current.speedMps / Math.max(1, this.options.assistedCruiseMps)),
0.08,
1.35,
);
const commandedVerticalSpeed = Math.sin(this.current.pitchDeg * Math.PI / 180) *
this.current.speedMps * liftAuthority;
const stallSinkMps = this.current.stalled
? clamp((this.options.stallSpeedMps - this.current.speedMps) * 0.7 + 2.5, 2.5, 14)
: 0;
this.current.verticalSpeedMps = moveToward(
this.current.verticalSpeedMps,
commandedVerticalSpeed - stallSinkMps,
(this.current.stalled ? 8 : 5) * dt,
);
this.current.loadFactorG = clamp(
liftAuthority / Math.max(0.25, Math.cos(this.current.rollDeg * Math.PI / 180)),
0,
3.5,
);
const heading = this.current.headingDeg * Math.PI / 180;
const horizontalSpeed = Math.cos(this.current.pitchDeg * Math.PI / 180) * this.current.speedMps;
const northM = (Math.cos(heading) * horizontalSpeed + this.current.windNorthMps) * dt;
const eastM = (Math.sin(heading) * horizontalSpeed + this.current.windEastMps) * dt;
const nextLat = this.current.lat + northM / EARTH_RADIUS_M * 180 / Math.PI;
const nextLng = this.current.lng + eastM /
(EARTH_RADIUS_M * Math.max(0.01, Math.cos(this.current.lat * Math.PI / 180))) * 180 / Math.PI;
let nextAltitude = this.current.altitudeM + this.current.verticalSpeedMps * dt;
const groundElevationM = this.groundElevationM(nextLat, nextLng);
const wasVerticalSpeedMps = this.current.verticalSpeedMps;
this.current.onGround = nextAltitude <= groundElevationM + 0.75;
this.current.hardLanding = this.current.onGround && wasVerticalSpeedMps < -4.5;
if (this.current.onGround) {
nextAltitude = groundElevationM;
this.current.verticalSpeedMps = 0;
this.current.rollDeg = moveToward(this.current.rollDeg, 0, 70 * dt);
this.current.pitchDeg = moveToward(this.current.pitchDeg, 0, 45 * dt);
if (this.current.throttle < 0.55) {
this.current.speedMps = Math.max(this.options.minimumSpeedMps, this.current.speedMps - 4 * dt);
} else if (
this.current.speedMps > this.options.stallSpeedMps * 1.08 &&
this.current.pitchInput > 0.2
) {
this.current.onGround = false;
nextAltitude = groundElevationM + 0.8;
this.current.verticalSpeedMps = 0.8;
}
}
const envelope = this.options.envelope;
this.current.envelopeContact =
nextLat < envelope.minLat || nextLat > envelope.maxLat ||
nextLng < envelope.minLng || nextLng > envelope.maxLng ||
nextAltitude < envelope.minAltitudeM || nextAltitude > envelope.maxAltitudeM;
this.current.lat = clamp(nextLat, envelope.minLat, envelope.maxLat);
this.current.lng = clamp(nextLng, envelope.minLng, envelope.maxLng);
this.current.altitudeM = clamp(nextAltitude, envelope.minAltitudeM, envelope.maxAltitudeM);
this.current.groundClearanceM = Math.max(0, this.current.altitudeM - groundElevationM);
if (this.current.envelopeContact) {
this.current.speedMps = Math.max(this.options.minimumSpeedMps, this.current.speedMps * 0.92);
this.current.pitchDeg = moveToward(this.current.pitchDeg, 0, 90 * dt);
this.current.rollDeg = moveToward(this.current.rollDeg, 0, 90 * dt);
}
this.current.fanRadians = (this.current.fanRadians + (30 + this.current.throttle * 180) * dt) % TWO_PI;
const electricalPowerW = 8_000 + this.current.throttle * 122_000 +
Math.abs(this.current.verticalSpeedMps) * 420;
const usedWh = Math.min(this.current.batteryWh, electricalPowerW * dt / 3_600);
this.current.batteryWh -= usedWh;
this.current.energyUsedWh += usedWh;
this.current.elapsedSteps += 1;
}
}
export function replayAircraftInputs(
options: AircraftControllerOptions,
frames: readonly TimedAircraftInputFrame[],
): AircraftReplayResult {
const controller = new AircraftController(options);
const trajectory: AircraftControllerSnapshot[] = [controller.snapshot()];
for (const frame of frames) {
const steps = Number.isFinite(frame.steps) ? Math.max(0, Math.floor(frame.steps)) : 0;
const held = normalizeAircraftActions(frame.actions);
for (let index = 0; index < steps; index += 1) {
controller.stepFixed(index === 0 ? held : { ...held, modeRequest: "none", reset: false });
trajectory.push(controller.snapshot());
}
}
return { trajectory, final: trajectory.at(-1) ?? controller.snapshot() };
}
/** Renderer-neutral geographic chase camera derived from an authoritative pose. */
export function aircraftChaseCameraPose(
state: Readonly<AircraftControllerState>,
distanceBehindM = 24,
heightAboveM = 8,
lookAheadM = 35,
): AircraftCameraPose {
const heading = state.headingDeg * Math.PI / 180;
const geographicOffset = (northM: number, eastM: number): AircraftGeographicPoint => ({
lat: state.lat + northM / EARTH_RADIUS_M * 180 / Math.PI,
lng: state.lng + eastM /
(EARTH_RADIUS_M * Math.max(0.01, Math.cos(state.lat * Math.PI / 180))) * 180 / Math.PI,
});
const behind = geographicOffset(-Math.cos(heading) * distanceBehindM, -Math.sin(heading) * distanceBehindM);
const ahead = geographicOffset(Math.cos(heading) * lookAheadM, Math.sin(heading) * lookAheadM);
return {
position: { ...behind, altitudeM: state.altitudeM + heightAboveM },
target: { ...ahead, altitudeM: state.altitudeM + state.verticalSpeedMps * 0.4 },
rollDeg: state.rollDeg * 0.2,
};
}