2.4.7.3 Cylindrical Lights

The cylinder keyword specifies a cylindrical light source that is great for simulating laser beams. Cylindrical light sources work pretty much like spotlights except that the light rays are constrained by a cylinder and not a cone. The syntax is:

CYLINDER_LIGHT_SOURCE:
    light_source
    {
        <Location>, COLOR cylinder
        [LIGHT_MODIFIERS...]
    }
LIGHT_MODIFIER:
    SPOTLIGHT_ITEM | AREA_LIGHT_ITEMS | GENERAL_LIGHT_MODIFIERS
SPOTLIGHT_ITEM:
    radius Radius | falloff Falloff | tightness Tightness |
    point_at <Spot>

Default values:

  radius:     0.75 degrees
  falloff:    1    degrees
  tightness:  0

The point_at, radius, falloff and tightness keywords control the same features as with the spotlight. See "Spotlights" for details.

You should keep in mind that the cylindrical light source is still a point light source. The rays are emitted from one point and are only constraint by a cylinder. The light rays are not parallel.