Linear perspective where parallel lines in space are seen as a fan of lines in the image. Stereo where the differences between two views are exploited. Finally obtain an object-centred description where the shape of the objects is represented in a way that is independent of camera position. Constructive solid geometry uses building blocks such as cubes and wedges. Generalised cylinders can be used to represent approximately a wide range of shapes.
Hierarchical systems allow the breakdown of complex shapes into simpler ones.
I showed a slide of a hierarchical representation proposed for bipeds and quadrupeds. Product inspection - from printed circuit boards to fruit and fish. Autonomous vehicles - cars that drive themselves on freeways and autobahns, lunar and martian rangers. Progress is slow. Techniques are fragmentary.