Research On Key Technologies Of CACD Based On Subdivision Surfaces And FFD

The process of product design includes four sub phases: conceptual design, embodiment design, detail design and implementation design. Among them, the conceptual design phase is decisive. At present,the CAD software mainly aims at detail design, and is scarce of support for conceptual design.In this paper, a new system is proposed to support computer aided concept design. Shape modeling and modifying in CACD system are researched.NURBS is the main surface representation method in present CAD system. NURBS is suitable for precise modeling in the detail design phase, but is inconvenient for shape definition in the conceptual design phase. Subdivision surface is a promising modeling method to take over NURBS, for its advantage of arbitrary topology suitability and local topologically adjusting convenience under different refinement levels. Subdivision surface and its application in CACD system are lucubrated.In order to modify the shape of models, a new method of free-form deformation is put forward. This method is based on t-FFD, and it brings the subdivision surface into FFD field. To contribute the reflection between control lattice and the model, this method use subdivision surface. And testified the method from continuity and partly modify ability. To speed the response, methods of the parameterization and modify are proposed.