8

1146 Chapter 15: Lights and Cameras

Top: Top view of a target directional light

Bottom: Perspective view of the same light

Directional lights cast parallel light rays in a

single direction, as the sun does (for all practical

purposes) at the surface of the earth. Directional

lights are primarily used to simulate sunlight. You

can adjust the color of the light and position and

rotate the light in 3D space.

Atargetdirectionallightusesatargetobjectto

aim the light.

Because directional rays are p ara llel, directional

lights have a beam in the shape of a circular or

rectangular prism instead of a "cone."

Note: When you add a target d irectional light, the

software automatically assigns a

Look At controller

(page 2–329)

to it, with the light’s target object

assigned as the Look At t arget. You can use the

controller settings on the Motion panel to assign

any other object in the scene as the Look At t arget.

Note: Direct lights are supported in a

radiosity

solution (page 3–50)

only if they are pointed

downwards, outside the boundary box of the scene

geometry.

Note: The mental ray renderer assumes that all

directional lights come from infinity , so objects

thatarebehindthedirectlightobjectinthe

3dsMaxscenewillalsobeilluminated. In

addition, with the mental ray renderer , directional

lights cannot generate area shadows, and do not

workwiththeBeamshader(inthelumelibrary).