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370 Chapter 19: Video Post-Production
Alpha channels are used to composite one image
seamlessly over the top of another. If you want to
compos ite a lens flare, or an image that contains a
lens flare, over the top of another image, enable
this option. If you are not rendering to a 32-bit file,
do not enable this option.
Affect Z Buffer —The Z-Buffer stores an object’s
distance from the camera. The Z-Buffer is useful
for optical effects such as fog. When this option
is enabled, the linear distance of the lens flare is
recorded, and can be used in special effects that
make use of the Z-Buffer, for example, the
Focus
(page 3–377)
effect. To use Focus with a lens flare,
enable this option.
Occl usion Ra dius—Aradiusaroundthecenter
of the flare that determines when the lens flare
effectwillbegintofadeasitpassesbehindanother
object.Thisradiusismeasuredinpixels.
When the lens flare or scene is animated and the
source of the lens flare goes b ehind another object,
if occlusion is enabled, the flare dies down and
disappears until the s ource object reappears on the
other side of the hiding object. The radius makes
the flare gently fade when it is occluded, instead of
blink ing out.
Motion B lur—Determines whether or not an
animated lens flare is rendered using Motion
Blur. Motion Blur renders multiple copies in
short increments to the same frame, which gives
the illusion of a blurred object in motion. When
an object is moving rapidly across the screen, it
animates more smoothly if motion blur is turned
on. Using motion blur can add considerable time
to your rendering.
You can set the amount of blur with the Motion
Blur spinner. Values range from 0 to 100, and are
based on the number of samples the motion blur
should use.
Ax ial Trans parency —Astandardcircular
transparency gradient that affects the transparency
of the lens flare secondary elements along their
axis and relative to their s ource. This lets your
secondary elemen ts be brighter on one side than
the other, adding extra realism to your flare effects.
Render—Specifies whether or not each part of the
lens flare is rendered in t he final image. Use this
set of check boxe s to turn parts of the lens flare on
and off.
Note: Effectssuchassecondaryflaresareavailable
in sets. The Render button and Off Scene
determine whether the secondary flares are present
in the scene. The individual secondary flare sets
are controlled on their respective pages.
Off S cene—Specifieswhetherornotlensflaresthat
have their sources outside the scene will affect the
image. For example, if a lens flare source is just
off the edge of a frame, the secondary flares, and
possibly the star or ring, could still be showing on
the screen. Without Off Scene, the lens flare does
notappearatall.Youcanturnthisoptiononoroff
for each part of the flare.
Sq ueeze—Specifies whether the Squeeze sett i ng
affects a particular part of the lens flare. This
settin g depends on the Squeeze setting in the lens
flare properties.
Inferno—Defines whether the inferno (page 3–376)
sett ings are active for this portion of the lens flare.
Occlusion—Defines the percentage of the flare part
thatappearswhenitisoccludedbyanotherobject.
A value of 100 ind ic ates that the whole object wi ll
disappear. Lower settings cause the lens flare to
wrap around the occluding object, making it fade,
butnotdisappearentirely.Forexample,ifyou
look at a cylinder with a brig ht light behind it,
the light ma kes the cyl inder appear thinner at the
brightest areas.
Note: The Occlusion spinners work in conjunction
w ith the Occlusion Radius spinner in the top right
of the Preferences panel.