2.5D (visual perception)
term in visual perception
Two-and-a-half-dimensional (2.5D) perception is an effect in visual perception. It is the construction of an apparently three-dimensional environment from 2D retinal projections. While the result is technically 2D, it allows for the illusion of depth. It is easier for the eye to discern the distance between two items than the depth of a single object in the view field. Computers can use 2.5D to make images of human faces look lifelike.
Perception of the physical environment is limited because of visual and cognitive issues. The visual problem is the lack of objects in three-dimensional space to be imaged with the same projection, while the cognitive problem is that the perception of an object depends on the observer. David Marr found that 2.5D has visual projection constraints that exist because "parts of images are always (deformed) discontinuities in luminance". Therefore, in reality, the observer does not see all of the surroundings but constructs a viewer-centred three-dimensional view.
Blur perception
A primary aspect of the human visual system is blur perception.
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