The lighting in a scene is determined by the number, type, and nature of the light sources defined in the input file. Available light sources range from simple directional sources to more realistic but computationally costly quadrilateral area light sources. Typically, you will want to use point or directional light sources while developing images. When final renderings are made, these simple light sources may be replaced by the more complex ones.
No matter what kind of light source you use, you will need to specify its intensity. In this chapter, an <#266#>Intensity<#266#> is either a red-green-blue triple indicating the color of the light source, or a single value that is interpreted as the intensity of a ``white'' light. In the current version of <#267#><#1809#>rayshade<#1809#><#267#>, the intensity of a light does not decrease as one moves farther from it.
If you do not define a light source, <#268#><#1811#>rayshade<#1811#><#268#> will create a directional light source of intensity 1.0 defined by the vector (1., -1., 1.). This default light source is designed to work well when default viewing parameters and surface values are being used.
You may define any number of light sources, but keep in mind that it will require more time to render images that include many light sources. It should also be noted that the light sources themselves will not appear in the image, even if they are placed in frame.