Why Distant Bodies Look Round, and the Shadows of Plants
A square loses its corners with distance; how plant shadows fall with the sun left or right
Leonardo explains that any shadowy body, whatever its shape, appears spherical at a great distance: a square first loses its corners, then its lesser sides, just as a distant man loses legs, arms and head before the torso, until it reads as round. A small squared figure is drawn in the text to illustrate this, keyed to points b and c for a tree's vanishing branch-form. A further chapter (citing Book B, folio 19) argues that plant shadows do not fall the same on right-hand and left-hand plants, especially when the sun is to one side, and cites three rules on how opaque bodies read shadowy, illuminated, or half-and-half depending on where the eye stands relative to the light.
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At distance every shape becomes spherical
Every shadowy body, of whatever figure, appears spherical at a long distance: a square first loses its corners, then more of its lesser remaining sides. Before the whole is lost the smaller parts are lost, as a distant man loses legs, arms and head before the torso, until, the corners gone, the form reads as round.
Diagram: a square drawn to show corners lost with distance
A small squared figure is drawn within the text beside the argument, illustrating how a square body sheds its angles at distance. The passage also keys a tree's diminishing branch-form to points b and c, where at b it nearly vanishes and at c the whole plant is barely recognized.
Plant shadows differ on the right and left with the sun aside
The shadows of plants set in landscapes do not clothe right-hand and left-hand plants in the same disposition, above all when the sun is to the right or left. This is proven by rules that opaque bodies between light and eye read all shadowy, that the eye between body and light sees it all illuminated, and that eye and body between darkness and light appear half shadowy and half luminous.