Orthogonal Projection In MS Paint

Orthogonal projection mean "right angled" or in mathematics it is "perpendicularity". In art, you can draw a 3 dimentional shape or perspective using orthogonal projections.

3D orthogonal projection

Similarly, you can draw 2 dimensional orthogonal projections. Below figure has two orthogonal shapes from same objects in different perspective.

Orthogonal Shapes

Both shapes in the above figure have one thing common and that is they are right angled. One in 3 dimensional space and other in 2 dimensional space.