Abstract
In the shape modeling with 3D CAD systems, the trimmed surface is quite popular. For instance, Japanese Industrial Standards (JIS) models contain a lot of notches, expressed using trimmed surfaces. Since trimmed surfaces are directly modified in direct modeling, it has a big restriction in the shape modification. It is effective to apply a new free-form surface to a closed region composed of the modified edges because the consistency of a trimmed surface can be maintained. This paper proposes the method of fitting a free-form surface by using the offset curve. To be more concrete, an offset curve is generated according to the tangent planes and a point cloud is generated. After that, a B-spline surface is generated using the generated point clouds and the boundary curves, so that a new trimmed surface is generated. Our method is effective for direct modeling that directly modifies the boundary edges of the trimmed surface representing a notch shape.
