Stages of Vision
Marr described vision as proceeding from a two-dimensional visual array (on the retina) to a three-dimensional description of the world as output. His stages of vision include
- a primal sketch of the scene, based on feature extraction of fundamental components of the scene, including edges, regions, etc. Note the similarity in concept to a pencil sketch drawn quickly by an artist as an impression.
- a 2.5D sketch of the scene, where textures are acknowledged, etc. Note the similarity in concept to the stage in drawing where an artist highlights or shades areas of a scene, to provide depth.
- a 3 D model, where the scene is visualized in a continuous, 3-dimensional map.
Francis Crick noted that this insight although seminal, has been somewhat modified.
2.5D sketch is related to stereopsis, optic flow, and motion parallax. The 2.5D sketch represents that in reality we do not see all of our surroundings but construct the viewer-centered three dimensional view of our environment. 2.5D Sketch is a paraline drawing and often referred to by its generic term "axonometric" or "isometric" drawing and are often used by modern architects and designers.
Read more about this topic: David Marr (neuroscientist)
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