Marr's two-dimensional perception is based on the transmission of information from the world around you to your eyes. He explains that this information is not substantive, as it provides no method for analysis of the received information and only a sense of what is happening. He relates it to an artist taking a few moments to sketch a scene with a pencil. The artist may succeed at recording some of the main events occurring in front of her but cannot grasp the full scene. The two-dimensional model is an impression of the scene but ultimately false and lacking for any real information. This level of perception becomes the unanalyzed vision of the world.
Marr explains that with an intensive study of a scene, an artist can create a two-dimensional perspective that is fully explored. He compares this phenomenon with an artist watching a scene for an extended period and re-creating it on a page. The result is a scene rich in description, but ultimately an artist must use deceptive techniques to translate texture and depth. For instance, an artist cannot recreate a three-dimensional impression on a two-dimensional canvas without tricking the viewer into believing that depth exists. The result is still only an impression of the real scene. This level of perception becomes the represented reality you see when you look at a picture, television screen or painting.
Marr's three-dimensional perception is a full vision of an event or a scene. A three-dimensional scene captures depth, texture and events in a fully realized format. As a level of perception, this vision translates the entire scene to the viewers. This level of perception equates essentially to a viewer who is actually perceiving a situation firsthand rather than reviewing a situation from a representation of the event. Marr explains that a three-dimensional perception is the most true to the situation, offering the most information to the viewer.
The two-dimensional perception provides little information to review or analyze. The result is a perception skewed toward focal points, chosen by the creator of the image, such as an artist who sketches one figure on a scene but eliminates other details. The 2.5-dimension perception provides much more information, allowing for a deeper analysis of the event; however, Marr explains that this perception remains your perception of the artist's perception and not actually reality. The three-dimensional perception provides a full opportunity for analysis based on a larger and complete perspective of a situation.