Abstract-A novel method is proposed in this paper for automatic acquisition of three-dimensional models of unknown objects by an active vision system, in which the vision sensor is to be moved from one viewpoint to the next around the target to obtain its complete model. In each step, sensing parameters are determined automatically for incrementally building the 3D target models. The method is developed by analyzing the target's trend surface, which is the regional feature of a surface for describing the global tendency of change. Whilst previous approaches to trend analysis are usually focused on generating polynomial equations for interpreting regression surfaces in three dimensions, this paper proposes a new mathematical model for predicting the unknown area of the object surface. A uniform surface model is established by analyzing the surface curvatures. Furthermore, a criterion is defined to determine the exploration direction and an algorithm is developed for determining the parameters of the next view. Implementation of the method is carried out to validate the proposed method.Index Terms-vision sensor, viewpoint planning, sensor placement, 3D modeling, trend surface, surface prediction, model acquisition.