*** Problems on the use of perspective in art ***

	1. How many vanishing points can there be in a perspective drawing?


	2. Does a pair of lines parallel to the picture plane converge?


	3. How to avoid distortion of objects in wide-angle perspectives?

	o Leonardo's paradox - in wide-angle linear perspective views, objects
	near the edges of the canvas look distorted.  Switching to a curved
	(cylindrical or spherical) perspective fixes this, but straight lines
	now appear curved.
		-> Dubery and Willats, row of columns
			o linear perspective, p. 84
			o curvilinear perspective, p. 85