POV-Ray : Documentation : Camera Identifiers
  POV-Ray 3.6 Documentation Online View Camera Ray Perturbation   2.3.2 Atmospheric Effects Camera Identifiers

Camera identifiers may be declared to make scene files more readable and to parameterize scenes so that changing a single declaration changes many values. You may declare several camera identifiers if you wish. This makes it easy to quickly change cameras. An identifier is declared as follows.

    #declare IDENTIFIER = CAMERA |

Where IDENTIFIER is the name of the identifier up to 40 characters long and CAMERA is any valid camera statement. See "#declare vs. #local" for information on identifier scope. Here is an example...

 #declare Long_Lens = camera {
    location -z*100
    look_at <0,0,0>
    angle 3
 #declare Short_Lens = camera {
    location -z*50
    look_at <0,0,0>
    angle 15
 camera {
    Long_Lens  // edit this line to change lenses
    translate <33,2,0>

Note: only camera transformations can be added to an already declared camera. Camera behaviour changing keywords are not allowed, as they are needed in an earlier stage for resolving the keyword order dependencies. Camera Ray Perturbation   2.3.2 Atmospheric Effects

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