EID102 drafting errata:

Rules for drawing lines:
(one draws a line if -and only if- you see in the view being drawn):
1) a sharp edge
2) a curved surface that is zero degrees to your POV (point of view).

THAT'S IT! if the feature you are questioning doesn't match one of those 
2 rules, you don't draw a line!


In detail:
1) a sharp edge is defined as the line that is formed when two surfaces meet
at any angle ( other than zero ). Even if they meet at 0.01 degrees, a 
"sharp edge" is created, and if seen - must be drawn.
The surfaces may be curved or straight, but if they meet at any angle, 
it is considered a sharp edge.

2) any curved surface that becomes tangent (zero degrees) from your POV is 
drawn as a line. This will always happen when a curved surface curves back 
on itself (like the outer limits of a cylinder or sphere), but the surface 
need not curve back on itself - see examples below:


images for examples

example 1: a cube - the sides meet at 90 degrees, therefore they are seen 
as lines using rule #1. The resulting view is a square.

example 2: a cylinder -  the top and bottom are seen as lines because of 
rule #1, and the sides are seen as lines because of rule #2. the resulting 
view is a square (yes, the side views of a cylinder and a cube are identical. 
this is okay! you get the depth information from the other views).

example 3: boot #1 - the sides are drawn via rule #1 (side surfaces meeting 
curved surfaces). The top and bottom follow the same rule. There is an 
additional line in the middle from where the curved surface becomes tangent 
to the observers POV.

example 4: boot #2 - sides and top/bottom are same as ex#3; however, there is
no line in the middle because the curved surface never comes to zero degrees.

example 5: wacky thingie #1 - left side is rule #2, right side is rule #1, 
top and bottom are rule #1, but note that while they are continuous lines, 
they ACTUALLY are describing the protruding  part and the back part.
There is a line in the middle where the outer edge of the protrusion curves back
on itself.

example 6: wacky thingie #2 - it's just ex#1 placed under ex#2 !

example 7: super wacky thingie -