Occlusion-free Camera Control

Computing and maintaining the visibility of target objects is a fundamental problem in the the design of automatic camera control schemes for {3D} graphics applications. Most real-time camera control algorithms only incorporate mechanisms for the evaluation of the visibility of target objects from a single viewpoint, and typically idealise the geometric complexity of target objects in doing so. We present a novel approach to the real-time evaluation of the visibility of multiple target objects which simultaneously computes their visibility for a large sample of points. The visibility computation step involves performing a low resolution projection from points on pairs of target objects onto a plane parallel to the pair and behind the camera. By combining the depth buffers for these projections the joint visibility of the pair can be rapidly computed for a sample of locations around the current camera position. This pair-wise computation is extended for three or more target objects and visibility results aggregated in a temporal window to mitigate over-reactive camera behaviour. To address the target object geometry idealisation problem we use a stochastic approximation of the physical extent of target objects by selecting projection points randomly from the visible surface of the target object. We demonstrate the efficiency of the approach for a number of problematic and complex scene configurations in real-time for both two and three target objects