||Geometric modeling of complex objects is a difficult task. Free-form deformation (FFD) is a powerful tool for modeling complex objects. However, using FFD is sometimes difficult. In this thesis, FFD for parametric trimmed surfaces is presented. This method uses NURBS FFD to modify the shape of parametric trimmed surfaces. A feature-based FFD method is presented for 3D Garment CAD application. Trimmed surface development is primarily used for flattening a 3D surface into a corresponding 2D pattern or surface. This thesis presents a general method for parametric trimmed surface development. This method can be applied in computer aided design, texture mapping, ship building, etc. First, the surface is triangulated and mapped onto a plane. This initial planar mapping has the same topology as its original surface. Then, a spring-mass system is applied to deform the initial planar mapping. The resulting surface elastic deformation energy distribution is indicated by a color graph, which determines a surface cutting line. The method presented in this thesis can efficiently solve development problems for complex trimmed surfaces. Accuracy of a developed surface can easily be controlled locally. Thus, compared to earlier methods, this method provides more flexibility for solving CAD and CAM surface problems. As a prior step to surface free-form deformation and surface development, an improved trimmed surface triangulation method is also presented. The algorithm first constructs triangles in parametric space, then adjusts the shapes of triangles in model space. As a result, the algorithm guarantees a good triangular mesh in model space.