1. A method of creating a 3D model of a 3D object, comprising: providing a 2D sketching mode for drawing sketches by: receiving a specification of a first 2D plane having a first position in a 3D space; receiving a drawing of a first sketch on the first 2D plane; and receiving a specification of a second 2D plane having a second position in the 3D space, wherein the second position is different from the first position, the second 2D plane comprising a second sketch; and providing a 3D geometry mode that uses the first sketch on the first 2D plane and the second sketch on the second 2D plane as references to produce a first 3D geometry curve and a second 3D geometry curve, the first 3D geometry curve and the second 3D geometry curve connecting the first 2D plane and the second 2D plane, wherein a 3D surface geometry of the 3D object is defined by the first sketch on the first 2D plane, the second sketch on the second 2D plane, the first 3D geometry curve, and the second 3D geometry curve.