The method for on-screen animation includes providing a digital world including image object elements and defining autonomous image entities (AIE). Each AIE may represent a character or an object that is characterized by i) attributes defining the AIE relatively to the image objects elements of the digital world, and ii) behaviours for modifying some of the attributes. Each AIE is associated to animation clips allowing representing the AIE in movement in the digital world. Virtual sensors allow the AIE to gather data information about image object elements or other AIE within the digital world. Decision trees are used for processing the data information resulting in selecting and triggering one of the animation cycle or selecting a new behaviour. A system embodying the above method is also provided. The method and system for on-screen animation of digital entities according to the present invention can be used for creating animation for movies, for video games, and for simulation.