Isometric drawings are 3D drawings. They show three sides, all
in dimensional proportion, but none are shown as a true shape
with 90 degree corners. All the vertical lines are drawn
vertically but all horizontal lines are drawn at 30 degrees to
the base line. Isometric is an easy method of drawing 3D images.
Oblique drawings are also used in engineering. The object is
drawn with the most distinguishing features facing directly
towards the observer, showing the true shape of these features.
Circular features like round holes can be drawn on this front
face as true circles. In other 3D forms, circular features must
be drawn as ellipses. To show the 3D effect, parallel lines
(called 'lines of sight') are drawn from the front face at an
angle. The cavalier method is the simplest form of oblique
projection. All features in the oblique projection view are
drawn to the same scale eg 1:1, and the lines of sight are drawn
at 45° to the horizontal as shown in the diagram. The lines of
sight may appear to diverge excess