Similar to the Sampler Info node, Light info provides light information instead of surface property information. You use the Light Info utility node to obtain information about the position of a light relative to a texture. As each point on the texture is shaded, the attributes of Light Info can determine the precise distance from the light to the point being shaded.
Find this utility in the Create Bar (see Hide, resize or customize the Create bar).
To use this utility, see Use the Light Info utility. The Light Info attributes reside in the Connection Editor.
The world-space distance between the connected light and the point on the surface being shaded.This can be calculated in different ways. See Light Direction Onlyfor details.
Controls how the Sample Distance attribute is calculated. If off, the Sample Distance is the world-space distance from the light to the point being sampled.
If on, the Sample Distance is the distance along the light direction vector to the closest point on that vector to the point being sampled.
In mathematical terms, it returns the length of the projection of the light-to-object vector onto the light-direction vector.