touch-orbit

touchOrbit(camera) gives an ArcRotateCamera the touch map in touch-gesture: one finger orbits, two fingers moving together pan, a pinch zooms. The decision is made once per gesture. <tosi-b3d>'s default camera and orbitCam both call it; call it yourself on an ArcRotateCamera you build (tosijs-3d#52).

• Pan follows the fingers. The centroid's pixels become world units at the TARGET's depth (2·r·tan(fov/2) per viewport height), applied straight to the target, so the point you touched moves with you. Babylon's own two-finger pan is a fixed 1/panningSensibility fed through its inertia, so 150 px moved the target 0.76 m at 8 m and got slower relative to the view the further out you were.
• Zoom is natural (radius × previous spacing / spacing), clamped to the camera's radius limits.
• One finger is untouched. Only the two-finger path is replaced.

Returns a function that restores Babylon's handler.