OrbitControls touch crashes on Expo mobile app

[williamdsw]

• three version: ^0.166.1
• @types/three version: 0.183.1
• three-stdlib version: ^2.35.6

Problem description:

As previously reported by @damistheanswer in the issue mrdoob/three.js#32116, OrbitControls does crash a mobile app on touch devices, such tablets and iPads, when using multi-touches to zoom in/zoom out an object.
I got the same message such as:

TypeError: Cannot read properties of undefined (reading 'x')

Reproduction steps

1. Download the sample project or the apk file
2. Start a two-finger pinch gesture (pinch-to-zoom)
3. Lift one finger mid-gesture while the other finger remains touching
4. The error occurs sporadically when the second pointer position becomes undefined

Relevant code:

Same as the issue #32116

In OrbitControls.js, the _getSecondPointerPosition() method returns undefined when a pointer is no longer tracked:

// Line ~1407-1411
_getSecondPointerPosition( event ) {
    const pointerId = ( event.pointerId === this._pointers[ 0 ] ) ? this._pointers[ 1 ] : this._pointers[ 0 ];
    return this._pointerPositions[ pointerId ]; // Can return undefined!
}

This undefined value is then used without null checking in multiple places:

// Line ~1234-1238 (handleTouchMoveDolly)
const position = this._getSecondPointerPosition( event );
const dx = event.pageX - position.x; // ❌ Crash: position is undefined
const dy = event.pageY - position.y;

Similar crashes occur at:

• Line 1202-1204 (handleTouchStartRotate)
• Line 1221-1223 (handleTouchStartPan)
• Line 1269-1271 (handleTouchMoveRotate)
• Line 1298-1300 (handleTouchMovePan)
• Line 1317-1320 (handleTouchMoveDolly)

Live example

Same as the issue #32116:

1. User starts two-finger gesture → both pointers tracked in _pointers array
2. User lifts one finger → pointer is removed from _pointers
3. Move event fires for remaining finger → tries to get second pointer position
4. _pointerPositions[pointerId] returns undefined because pointer was removed
5. Code attempts position.x → crash

Screenshots

Attached error on expo app:

Please check this video for demonstration of the bug:

Device

Mobile

OS

Android