The results so far of our observations

Summary of our Conclusions
Lines in Space and their Perspective Images

	A line in space that is parallel to the picture plane	Appears exactly the same in the image (except smaller) as it does in real-life, and has no vanishing point. Lines that are parallel to each other as well as being parallel to the picture plane will have parallel perspective images.
	Any line in space that is not parallel to the picture plane	The perspective image of any such line has a vanishing point. The vanishing point will be wherever a line from the viewer's eye parallel to the actual 3D line passes through the picture plane. Because the vanishing point is determined by a line of sight parallel to the actual 3D line, all lines that are parallel in space share the same vanishing point in the perspective image (which of course means their images willl not be parallel).
	Specific Case: Lines which are orthogonal (perpendicular) to the picture plane	The images of such lines vanish at the origin. To get the full sense of depth intended by the artist, viewers should place their eyes directly opposite this point. How far back should they place it? We'll be talking about that shortly! The horizontal line through this primary vanishing point is called the horizon line