This section explains how humans judge the distance from their eyes to objects in the real world using vision. The perceived distance could be metric, which means that an estimate of the absolute distance is obtained. For example, a house may appear to be about meters away. Alternatively, the distance information could be ordinal, which means that the relative arrangement of visible objects can be inferred. For example, one house appears to be closer than another if it is partially blocking the view of the further one.