1. A method for resolving collisions for placement of objects in three dimensional models, the method comprising: attributing a first state to each object having a hard spatial volume and a second state to each object having a soft spatial volume; predefining a first set of rules to determine whether multiple objects may occupy the same spatial volume based on the combination of the object states, the first set of rules covering all permutations of said first state and said second state; placing a first object in the three dimensional model; placing a second object in the three dimensional model; determining whether the first object has a collision with the second object in the three dimensional model; and resolving the collision based on said first predefined set of rules.