1. In a non-transitory computer readable storage medium having stored therein data representing instructions executable by a programmed processor for three-dimensional model determination from a two-dimensional sketch, the storage medium comprising instructions for: receiving the two-dimensional sketch having objects in a view plane of the user, the view plane of the user comprising x and y dimensions; assigning two-dimensional constraints to the objects of the two-dimensional sketch, the two-dimensional constraints defined in the x and y dimensions; assigning three-dimensional constraints to the objects of the two-dimensional sketch, the three-dimensional constraints defined in the x and y dimension as well as a z dimension orthogonal to the view plane; solving for three-dimensional positions of the objects as a function of the two- and three-dimensional constraints; determining a gap along the z dimension based on the three-dimensional positions; altering relative positions of the objects of the two-dimensional sketch in the view plane of the user such that the x, y, or x and y coordinates of at least one of the objects is different; and solving for the three-dimensional positions of the objects as a function of the altered relative positions.