Distortions are inevitable when flattening is applied to an irregular surface. This study presents a meshing energy model and evaluates the energy variation between the 3D designed surface and the 2D flattened pattern in order to minimize the energy that arises from the development process. Base on expert knowledge, constraint optimization methods are used to find the unique pattern in its minimum deformation. This method is applied via simulation to some garment examples. Taking design and manufacturing conditions into consideration, the designed garments are flattened into patterns which have the least energy and area variation from the 3D designs.