The Technology Of Freeform Surface Deformation Based On Constraints

Deformation technology is an important tool in geometric modeling and computer animation. The deformation technology can simulate many deformations such as the deformation of flexible objects, which is unable to achieve by traditional modeling and computer animation method. However, it's not an easy work to perform intuitive interaction by using the conventional free-form deformation methods, because of either inconvenient control tools or large time and space costs. Especially in the process of actual applications, engineers need a good grip on some mathematical principles besides essential tools when NURBS surface is deformed. So it is very difficult for deformation surface and the efficiency of developing is low.This thesis proposes freeform surface deformations based on the FFD thought,which uses constraints and features for surface deformation. Users who have not mathematic knowledge can deform surface from angles of application. The paper's contents are:The thesis proposes freeform surface deformation methods based on point constraint which refers to the FFD thought and the Cao En model. Those methods should be based not only on the change of the mathematical parameters, but also on the user's specified constraints and feature shapes deformation representation. The model is a combination of two functions: a displacement function which represents how much the parent surface is deformed to produce a local shape deformation and a function for representing an existing NURBS surface called parent surface. Based on the surface model, the author develops three deformation methods which are named SPFFD, MPFFD, and SFFFD. The technique for freeform surface deformation allows conceptual designers to modify a parent surface by directly applying point constraints or a surface constraint to the parent surface.We present a novel based on spline constraint freeform surface deformation method which adopts a simple 3D sketching technique and external force constrain. User can decide the region to be deformed with bounding curve and decide the resultant surface with target curve. We also introduce a 3D sensor and a 3D dragger to control the target curve which aim for adjusting the resultant surface. Finally we propose a kind of feature presentation based on the method.Lastly, we conclude the thesis, and discuss the future application of our research.