POV-Ray : Documentation : 2.4.7.4 Parallel Lights
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2.4.7.3 Cylindrical Lights   2.4.7.5 Area Lights

2.4.7.4 Parallel Lights

syntax:

light_source {
  LOCATION_VECTOR, COLOR
  [LIGHT_SOURCE_ITEMS...]
  parallel
  point_at VECTOR
}

The parallel keyword can be used with any type of light source.

Note: for normal point lights, point_at must come after parallel.

Parallel lights are useful for simulating very distant light sources, such as sunlight. As the name suggests, it makes the light rays parallel.

Technically this is done by shooting rays from the closest point on a plane to the object intersection point. The plane is determined by a perpendicular defined by the light location and the point_at vector.

Two things must be considered when choosing the light location (specifically, its distance):

  1. Any parts of an object "above" the light plane still get illuminated according to the light direction, but they will not cast or receive shadows.
  2. fade_distance and fade_power use the light location to determine distance for light attenuation, so the attenuation still looks like that of a point source.
    Area light also uses the light location in its calculations.
2.4.7.3 Cylindrical Lights   2.4.7.5 Area Lights


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