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 point cloud thus creating a computerized inversed object, each point in the point cloud is translated to a corresponding point in the computerized inversed object, wherein the inversion is a monotonically decreasing function depending on the distance of a point of the computerized object from the viewpoint; b. computing a convex hull of the computerized inversed object and the viewpoint; c. determining a visibility of the specific point from a determined viewpoint according to whether the position of the corresponding point of the specific point is on the convex hull; wherein the computerized method is performed by a processor.