Surface

• A surface is a kind of geometry. RapidFrom provides NURBS(Non-uniform Rational B-Spline) surface as the surface geometry, which can be generated by user's definition of its boundary curve. Control point can reside in the bi-direction, U-direction and V-direction. The U-direction is determined based on the order of user's selection. That is, the direction of a curve that is picked first is defined as the U-direction.
• The surface is divided into 2 types, untrimmed and trimmed surface. The untrimmed surface has 4 boundary curves, while the trimmed surface has 2, 3, or more than 4 boundary curves. The trimmed surface is a special type of surface which is trimmed with its boundary curves after a 4-boundary surface surrounding all the user's selection curves is generated.