Insertion procedure:

   traverse tree to find leaf node n
   	    whose region contains vobj
   
   if (enough space in n)
   {
      insert vobj into corresponding page
   }
   else
   {
      need to perform local rearrangement in tree
         by splitting points between n and n's parent
         and n's siblings according to split heuristic
   }

Split heuristics include:

• minimise total volume of bounding regions

• minimise variance in volume of regions

• minimise overlap among regions

• .....