add comment for probeSpace
add comment for probeSpace

RaananW/Babylon.js,sebavan/Babylon.js,sebavan/Babylon.js,RaananW/Babylon.js,BabylonJS/Babylon.js,sebavan/Babylon.js,BabylonJS/Babylon.js,RaananW/Babylon.js,BabylonJS/Babylon.js