70 |
|
to the letter 'c'. |
71 |
|
This view is like a standard perspective vertically, but projected |
72 |
|
on a cylinder horizontally (like a soupcan's-eye view). |
73 |
< |
Two fisheye views are provided as well; 'h' yields a hemispherical fisheye |
74 |
< |
view and 'a' results in angular fisheye distortion. |
73 |
> |
Three fisheye views are provided as well; 'h' yields a hemispherical fisheye |
74 |
> |
view, 'a' results in angular fisheye distortion, and 's' |
75 |
> |
results in a planisphere (stereographic) projection. |
76 |
|
A hemispherical fisheye is a projection of the hemisphere onto a circle. |
77 |
|
The maximum view angle for this type is 180 degrees. |
78 |
|
An angular fisheye view is defined such that distance from the center of |
79 |
|
the image is proportional to the angle from the central view direction. |
80 |
|
An angular fisheye can display a full 360 degrees. |
81 |
+ |
A planisphere fisheye view maintains angular relationships between lines, |
82 |
+ |
and is commonly used for sun path analysis. |
83 |
+ |
This is more commonly known as a |
84 |
+ |
"stereographic projection," but we avoid the term here so as not to |
85 |
+ |
confuse it with a stereoscopic pair. |
86 |
+ |
A planisphere fisheye can display up to (but not including) 360 degrees, |
87 |
+ |
although distortion becomes extreme as this limit is approached. |
88 |
|
Note that there is no space between the view type |
89 |
|
option and its single letter argument. |
90 |
|
.TP |