POV-Ray Cyclopedia: Cylindrical Cameras

The first image is of a cylinder with a checkerboard pattern for the ground plane, and the Roman numerals 1 through 12 taking up positions around the camera. The "12" is in the +z direction. The "3" is in the +x direction. The "6" is directly behind the camera in the -z direction. The "9" is off to the left at -x. The image is 628 pixels wide by 100 pixels tall. This keeps with the 2*pi ration of the circumference of a circle. The code for the camera looks like this:

camera { cylinder 1
         location  <0.0, 0.5, 0.0>
         angle     360
         up        y
         right     x
         look_at   <0.0, 0.5,  1.0>
         }

The image of the camera (at right) shows the camera object, the projection plane (the semi-transparent red cylinder) and the upper and lower rays which are the limits of the cameras vertical view. The pink cylinders point straight ahead and show the middle of the image, the blue ones point directly to the sides and show the points exactly between the center of the image and the edges, and the green ones point directly back. The green cylinder is at the left and right end of the image this camera will see.
The Up and Right vectors need to be set to y and x, respectively, otherwise wierd things will happen such as:

This uses the following camera defintion:

camera { cylinder 1
         location  <0.0, 0.5, 0.0>
         angle     360
         up        y
         right     1.5*x
         look_at   <0.0, 0.5,  1.0>
         }

You can see that the sides of the projection plane are further from the camera and increasing the amout of zoom the camera has at that point, so the objects its looking at, names the "3" and the "9" are wider than the rest of the numbers. The objects are sitting on a cylinder, if they were on a plane then the horizon line would show a bit more distortion.

Here we have a camera shrunk in the y-direction:

camera { cylinder 1
         location  <0.0, 0.5, 0.0>
         angle     360
         up        0.5*y
         right     x
         look_at   <0.0, 0.5,  1.0>
         }

Everything gets taller, but there is no more room in width for the image so it distorts. They look normal if rendered at 628*50, which is 4pi:1 ratio.

Here we have a camera scaled up in the y-direction:

camera { cylinder 1
         location  <0.0, 0.5, 0.0>
         angle     360
         up        2*y
         right     x
         look_at   <0.0, 0.5,  1.0>
         }

Everything looks farther away because the viewing angle is too large

Lets touch breifly on the orthoganal horizontal cylinder

camera { cylinder 3
         location  <0.0, 0.5, 0.0>
         angle     360
         up        y
         right     x
         look_at   <0.0, 0.5,  1.0>
         }

The objects are all one unit tall, so they take up the entire hieght.

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