WorldWind Kotlin/earth.worldwind.gesture/PivotAnchorState

PivotAnchorState

class PivotAnchorState(engine: WorldWind, lookAt: LookAt)

Keeps a captured geographic anchor fixed under its original screen pixel while lookAt's range and/or heading change. Per-frame apply solves for lookAt.position via

L_new = A + s · Rotate(L_begin − A, axis = up_A, angle = −(H_new − H_begin)), s = R_new / R_begin

Pure zoom → identity rotation; pure rotation → s = 1. Sharing one instance across pinch / rotate / wheel handlers means simultaneous gestures compose into one self-consistent transform instead of fighting two separate anchors.

Sign of the rotation: heading is clockwise-from-north (right-hand rule axis = −up), so an increase in heading is a negative rotation around +up. Verified on the tangent-plane case L_begin=(0,0), A=(E,0), Δh=+90° → L_new=(E,−E).

Constructors

PivotAnchorState

constructor(engine: WorldWind, lookAt: LookAt)

Properties

isValid

var isValid: Boolean

Functions

apply

fun apply()

capture

fun capture(screenX: Double, screenY: Double): Boolean

Snapshots the anchor and the current lookAt state. Returns false (and leaves the state invalid, making apply a no-op) for off-globe screen points like the sky.

invalidate

fun invalidate()