1. A method of determining whether a specific point in a computerized image is visible from a viewpoint; said image is represented as a point cloud, the method comprising: a. performing inversion on points located in the vicinity of the specific point thus creating a computerized inversed object, each point in the vicinity of the specific point is translated to a parallel point in the computerized inversed object; b. defining a convex hull of the inversed object; c. determining if the specific point is visible from the viewpoint according to the position of its parallel point on the convex hull.