Any curvature in these lines can help reveal any undulations in the plane. To assess the number of texture units wide it is we can examine the units it contacts at its frontal edge. Its receding edge can be compared to a row of ground tiles it contacts. The height of a front surface has to be assessed as a proportion of the front edge, unless it contacts a flanking, erect texture unit. 15.Non-optical sources of information include familiar size.
Playing cards tend to be a particular size, for example.
The CN tower is a particular size, we may know. We can see parts that are usually concealed. The illusion is said to applied correctly in a full picture. Likely several factors contribute to particular illusions. Shape constancy is achieved despite variations in orientation.