Set up pan call back for current rgl device
pan3d(button)Integer from 1 to 3 indicating mouse button
Copied verbatim from ?rgl.setMouseCallbacks for rgl version 0.92.892 Mouse button 2 is right and button 3 is middle (accessed by Meta/Alt key)
Note that sometimes (parts of) objects seem to disappear after panning and
zooming. The example in rgl.setMouseCallbacks from which this
is copied includes a note that "this doesn't play well with rescaling"
if (FALSE) {
open3d()
pan3d(2)
}