9

Lens Effects Rendering Effects 225
different Lens Effect, even if the differences are
very smal l. For example, if you set up a Ray effect,
you will get slightly different rays in the lens flare if
you adjust the seed value.
Angle—Affects the amount that the Lens Effect
rotates from its default position, as the position of
the effect changes relative to the camera.
Sq ueeze—Squeezes the size of the overall
Lens Effect, either horizontally or vertically to
compensate for different frame aspect ratios.
Positive values stretch the effect hor i zontally, and
negative values stretch it vert ically. The value is
a percent age of the size of the flare. Range=100
to -100.
Lights group
Allows you to choose lights to apply Lens Effects to.
Pick Light—Enables you to select a light directly
through the viewpor ts. You can also selec t a light
by pressing
H to display the Select Ob jects dialog
(page 1–78).
Remove Light—Removes a selected light.
Drop-down list—Provides quick access to lights
that you have added to the Lens Effect.
Lens Effects Globals rollout, Scene panel
Affect Alpha—Specifies whether or not the Lens
Effect affects the alpha channel of an image w hen
the image is rendered in a 32-bit fi le format. The
alpha channel is an ext ra 8 bits of color (256
colors) that indicate transparency in an image.
Alpha channels are used to composite one image
seamlessly over the top of another. If you want to
composite a Lens Effect, or an image that contains
a Lens Effect, over the top of another i mage, enable
this option. If you are not rendering to a 32-bit file,
do not enable this option.
Affect Z Buffer—Stores an object’s distance from
the camera. The Z-Buffer is useful for optical
effects. When this option is enabled, the linear
distance of the Lens Effect is recorded, and can
be used in special effects that make use of the
Z-Buffer.
Distance Af fects—Allows distance f rom the camera
or viewport to affect the size and/or the intensity
of the effect.
Off-Center Affects—Allows an effect that is
off-center from the camera or viewport to affect
the size and/or the intensit y of the effect.
Direction Af fects—Allows direction of spot lights
with respect to the camera or viewport to affect
the size and/or the intensit y of the effect.
The size and intensity of the effect are at a
maximum when the light is pointed at the camera
(or viewpor t).
Occlusion group
Occlusion is used to determine w hen a Lens Effect
will be affected by an object th at comes between
the effect and the camera. By using two spinners
to determine occlusion you can have scene objects
realistically affect the look of your effect. The outer
radius will determine when another scene object
will begin to occlude and the inner radius will
determine when the scene object will cause the
effect to reach maximum occlusion.