Recent technological developments help us to acquire high quality 3D measurements of our urban environment. However, these measurements, which come as point clouds or Digital Surface Models (DSM), do not directly give 3D geometrical models of buildings. In addition to that, they are not suitable for fast 3D rendering. Therefore, detection and 3D reconstruction of buildings is an important research topic. We introduce a new active shape fitting algorithm for generating building models. Two significant improvements of the introduced method compared to our previous active shape algorithm are: (1) here, active shapes are initialized as cubes; and (2) the new energy function is computed by measuring the distances of the vertical cube faces to the building facade points and also by measuring the mean distance between the rooftop points and the top face of the cube. The proposed method helps to obtain 3D building models automatically even when the facade borders are difficult to detect because of neighboring trees or other objects. For testing the proposed approach, we use Airborne Laser Scanning (ALS) data of an area in Delft, The Netherlands. We compare the proposed 3D active shape fitting method with a previously developed 2D method. The results show the possible usage of the algorithm when simple and easy-to-render 3D models of large cities are needed.
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