Another novel example is Moustakas et al. 's (2005) project on 3-D model search using sketches. In the experimental system, the vector of geometrical descriptors for each 3-D model is calculated during the feature extraction stage. In the retrieval stage, a user can initially use one of the sketching interfaces (such as the virtual reality interface or by using an air mouse) to sketch a 2-D contour of the desired 3-D object. The 2-D shape is recognized by the system, and a sample primitive is automatically inserted in the scene. Next, the user defines other elements that cannot he described by the 2-D contour, such as the height of the object, and manipulates the 2-D contour until it reaches its target position. The final query is formed after all the primitives are inserted. Finally, the system computes the similarities between the query model and each 3-D model in the database, and renders the best matching records.