How does the orthographic projection matrix remap the scene?
Figure 1: the orthographic projection matrix remaps the scene bounding volume to the canonical view volume. All points contained in the scene bounding volume have their projected xy coordinates “normalized” (they lie within the range [-1,1]).
How is orthographic projection used in 3D modeling?
Orthographic projection can also be used to render shadow maps, or render orthographic views of a 3D model for practical reasons: an architect for example may need to produce blueprints from the 3D model of a house or building designed in a CAD software.
How is the bounding box of a scene computed?
The screen coordinates (the l, r, t and b parameters of the function) are computed as follows (lines 63-83): the bounding box of the scene is computed (we simply iterate over all vertices in the scene and extend the minimum and maximum extend variables accordingly).
When to use orthographic projection in a game?
You might think that orthographic projections are of no use today. Indeed, what people strive for whether in films or games, is photorealism for which perspective projection is generally used.
How is orthographic projection used in Sims city?
Famous games such the Sims or Sim City adopted this look. Orthographic projection can also be used to render shadow maps, or render orthographic views of a 3D model for practical reasons: an architect for example may need to produce blueprints from the 3D model of a house or building designed in a CAD software.
What is the goal of the orthographic matrix?
Once you have the bounding box for the scene, then the goal of the orthographic matrix is to remap it to a canonical view volume. This volume is a box which minimum and maximum extents are respectively (-1, -1, -1) and (1, 1, 1) (or (-1,-1,0) and (1,1,1) depending on the convention you are using).