A method and related CAD system and computer readable medium. A method includes loading an object model in a CAD system, the object model including a plurality of parts each of which may contain one or more shapes which in turn are composed of multiple polygons. The method includes adding the shapes to a spatial tree, the shapes each corresponding to at least one cell, each cell corresponding to a spatial region of the object model. The method also includes, for each cell that is too complex to process within a memory space of the CAD system, subdividing the cell into a plurality of subcells using a first subdivision process. The method also includes subdividing each cell into a plurality of subcells using a multi-threaded subdivision process, and combining the subcells into the spatial tree