We can start with the typical overview introduction, provided this time by Wikipedia:
Graphical projection is a protocol, used in technical drawing, by which an image of a three-dimensional object is projected onto a planar surface without the aid of numerical calculation. The projection is achieved by the use of imaginary “projectors”. The projected, mental image becomes the technician’s vision of the desired, finished picture. By following the protocol the technician may produce the envisioned picture on a planar surface such as drawing paper. The protocols provide a uniform imaging procedure among people trained in technical graphics (mechanical drawing, computer aided design, etc.).
There are two graphical projection categories each with its own protocol:
- parallel projection
- perspective projection
Fun With Parallel Projection
Lowering the angle of view and increasing the distance of the camera to infinity in a perspective projection results in a parallel projection:
Orthographic projection
The orthographic projection is derived from the principles of descriptive geometry and is a two-dimensional representation of a three-dimensional object. It is a parallel projection (the lines of projection are parallel both in reality and in the projection plane). It is the projection type of choice for working drawings.
In the image above we see an 3D representation of an object and on the side we see the 2D representation as elevation and plan views (more on that below).
The Glass Box
A common approach to thinking about orthographic projection is to think of an object existing in a glass box:
In rendering the front, sides, and back of the object are referred to as elevation views, while the top/bottom is called plan views.
Isometric projection
The images above are from the iOS game Monument Valley, and make use of isometric projection as a primary game mechanic.
The video below illustrates an isometric model that also transforms into non-isometric views as it moves, similar to the game Monument Valley.
#1 – Isometric City from Billy Chitkin on Vimeo.
This post is still under development. I’ll add more soon.
Technical Drawing 