hi, should the model''s center be 0,0,0 so say a sphere to sphere collsiion detection would work accurately or no matter where i place the object in it''s model space would also work accurately in sphere to sphere? also, i was wondering if you could help me with a formula for a sphere to box, many thanks,

Of course it should work accurately at any place. As to the intersection between box and sphere, it can not be solved within a formula. You can refer to http://www.gamasutra.com/features/19991018/Gomez_4.htm to get the algorithm.

Kidd