### Section 7.4.3Camera Ray Perturbation

The optional keyword normal may be used to assign a normal pattern to the camera. All camera rays will be perturbed using this pattern. This lets you create special effects. See the animated scene camera2.pov for an example.

### Section 7.4.4Placing the Camera

In the following sections the placing of the camera will be further explained.

### Section 7.4.4.1Location and Look_At

Under many circumstances just two vectors in the camera statement are all you need to position the camera: location and look_at. For example:

camera { location <3,5,-10> look_at <0,2,1> }

### Section 7.4.4.2The Sky Vector

Normally POV-Ray pans left or right by rotating about the y-axis until it lines up with the look_at point and then tilts straight up or down until the point is met exactly. However you may want to slant the camera sideways like an airplane making a banked turn. You may change the tilt of the camera using the sky vector. For example:

camera { location <3,5,-10> sky <1,1,0> look_at <0,2,1> }

### Section 7.4.4.3The Direction Vector

The direction vector tells POV-Ray the initial direction to point the camera before moving it with look_at or rotate vectors (the default is direction <0, 0, 1>). It may also be used to control the (horizontal) field of view with some types of projection. This should be done using the easier to use angle keyword though.

If you are using the ultra wide angle, panoramic or cylindrical projection you should use a unit length direction vector to avoid strange results.

The length of the direction vector doesn't matter if one of the following projection types is used: orthographic, fisheye or omnimax.

### Section 7.4.4.4Angle

The angle keyword 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.

The viewing angle is converted to a direction vector length and vice versa using the formula The viewing angle is given by the formula

```  angle = 2 * arctan(0.5 * right_length / direction_length)
```

where right_length and direction_length are the lengths of the right and direction vector respectively and arctan is the inverse tangens function.

From this the length of the direction vector can be calculated for a given viewing angle and right vector.

From this the length of the direction vector can be calculated for a given viewing angle and right vector.

```  direction_length = 0.5 * right_length / tan(angle / 2)
```

### Section 7.4.4.5Up and Right Vectors

The direction of the up and right vectors (together with the direction vector) determine the orientation of the camera in the scene. They are set implicitly by their default values of

right 4/3*x up y

While some camera types ignore the length of these vectors others use it to extract valuable information about the camera settings. The following list will explain the meaning of the right and up vector for each camera type. Since the direction the vectors is always used to describe the orientation of the camera it will not be explained again.

Perspective projection: The lengths of the up and right vectors are used to set the size of the viewing window and the aspect ratio as described in detail in section "Aspect Ratio". Since the field of view depends on the length of the direction vector (implicitly set by the angle keyword or explicitly set by the direction keyword) and the lengths of the right and up vectors you should carefully choose them in order to get the desired results.

Note that the up, right and direction vectors should always remain perpendicular to each other or the image will be distorted. If this is not the case a warning message will be printed. The vista buffer will not work for non-perpendicular camera vectors.

### Section 7.4.4.5.1Aspect Ratio

Together the right and up vectors define the aspect ratio (height to width ratio) of the resulting image. The default values up <0, 1, 0> and right <1.33, 0, 0> result in an aspect ratio of 4 to 3. This is the aspect ratio of a typical computer monitor. If you wanted a tall skinny image or a short wide panoramic image or a perfectly square image you should adjust the up and right vectors to the appropriate proportions.

For example:

camera { location <3,5,-10> up <0,1,0> right <1,0,0> look_at <0,2,1> }
Next Section