receding parallel lines definition

Receding parallel lines are lines parallel to each other that gradually move away from the viewer.  There are a number of rules that receding parallel lines follow in nature.  First, all lines in nature that are parallel to each other appear to converge at the same point as they recede from the viewer.  Second, all level lines that recede in nature appear to converge on the horizon.  Thirdly, inclining parallel lines in nature that recede appear to converge at a point immediately over the point they would have converged IF they had been level lines.  Fourthly, parallel lines in nature that recede when inclined downward appear to meet at a point immediately beneath the point they would have converged had they been level lines.