|Rectlinear will project on a flat surface. This
projection type is limited to a maximum FOV below 180 degrees. At a FOV
of 180° or more, the outermost rays wouldn't meet the surface any more.
Also, higher FOVs will make the image appear distorted on the edges as
you can see in the example picture below.
Rectlinear projection at a FOV of 160°
|Cylindrical will cast its rays on a cylinder from
inside. This gives you a maximum horizontal FOV of 360 degrees (the full
circle) but for the vertical FOV the same limits apply as for the
For printing purposes, you will unwrap the hull of the cylinder on a
flat surface. Edges will not look that distorted but lines that are not
exactly vertical may look heavily distorted.
|Equirectangular is capable of displaying the full
360 degrees horizontal as well as the 180 degrees vertical. It is the
unwrapped surface of a bubble and the distortions are the same as you
will know from a world map.
This projection type also will bend straight lines but it will look
quite natural as long as you don't use the vertical FOV near the 180°
This projection is most commonly used for so called