Parallel Projections

Now follow up with details on types of parallel projections!

orthographic 1

projectors are orthogonal to image plane, image plane is parallel to one face of the object

orthographic 2

preserves both distances and angles on faces parallel to the image plane

orthographic 3

ignores the z coordinate and keeps x and y as they are

axonometric 1

projectors are orthogonal to the image plane, image plane can have any orientation wrt the object, i.e., we see some of the sides not just the front face

axonometric 2

most useful with regular, rectangular shaped objects

3 types of axonometric projections

isometric, dimetric and trimetric

isometric

image plane symmetric wrt three principal faces, foreshortening of lines is the same in all directions

dimetric

image plane symmetric wrt two principal faces, two different foreshortening ratios

trimetric

projection is most general, no symmetry and different foreshortening ratio for each principal face

oblique

projectors are not parallel to image plane, they pass through the image at an oblique angle