Parallel projection is a form of perspective projection with infinite focal length (zoom). A subcategory of parallel projection is called pictorials. This entails a skewed view of an object in order to show all three axes in a single picture, the main skew being from the omission of any kind of scaling. This makes it somewhat akin to an orthographic projection. Because of this skew, any form of pictorial will always have some sort of distortion.
Yet, despite this distortion, pictorials can be very useful for game design as they can show us a three-dimensional game world on a flat surface using only tiles and sprites. Hereby, it's important to realize that there isn't only one type of pictorial projection. We can distinguish the following categories and subcategories:
Axonometric:
Isometric
Dimetric
Trimetric
Oblique
What distinguishes the types of axonometric projections is the exact angle at which the view deviates from the orthogonal. This is illustrated in...