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The angle keyword followed by a float expression specifies the (horizontal) viewing angle in degrees of the camera used. Even though it is possible to use the direction vector to determine the viewing angle for the perspective camera it is much easier to use the angle keyword.
When you specify the angle, POV-Ray adjusts the length of the direction vector accordingly. The formula used is direction_length = 0.5 * right_length / tan(angle / 2) where right_length is the length of the right vector. You should therefore specify the direction and right vectors before the angle keyword. The right vector is explained in the next section.
There is no limitation to the viewing angle except for the perspective projection. If you choose viewing angles larger than 360 degrees you'll see repeated images of the scene (the way the repetition takes place depends on the camera). This might be useful for special effects.
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