1. A method for detecting activation of a virtual sensor in a scene, wherein the virtual sensor comprises data representing a three-dimensional geometric form, data representing a position in the scene and data representing one or several trigger conditions, the method comprising: capturing a first data representation of the scene using at least one physical sensor; and determining whether one or several of the virtual sensor trigger conditions is/are fulfilled based on an analysis of the captured first data representation in a first volume area corresponding to the geometric form and position of the virtual sensor, wherein the determining whether a virtual sensor trigger condition is fulfilled comprises analyzing point cloud data representing surfaces of objects detected by the at least one physical sensor in the scene, the point cloud data comprising data representing non-empty points of a second volume area corresponding to the captured first data representation and respective associated position in the second volume area and determining whether an object of the scene enters the first volume area corresponding to the geometric form and position of the virtual sensor by determining whether a number of non-empty points whose position fall in the first volume area which correspond to the geometric form and position of the virtual sensor is beyond a threshold specified by a trigger condition.