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354 Chapter 19: Video Post-Production
Inter face
Affect Alpha—Specifies whether or not the lens
flare affects the alpha channel of an i mage, when
the image is rendered in a 32-bit fi le format. The
alpha channel is an extra 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
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 B uffer—The Z-Buffer stores an object’s
distance from the c amera. 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 3–362) effect. To use Focus with a lens flare,
enable this option.
Occlusion R adius—Aradiusaroundthecenter
of the flare that determines w hen the lens flare
effectwillbegintofadeasitpassesbehindanother
object.Thisradiusismeasuredinpixels.
When the lens flare or scene is animated and the
source of the lens flare goes behind another object,
if occlusion is enabled, the flare dies down and
disappears until the source object reappears on the
other side of the hiding object. The radius m akes
the flare gently fade when it is occluded, instead of
blinking 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
theillusionofablurredobjectinmotion.When
an object is moving r apidly across t he 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. Va lues r ange from 0 to 100, and are
based on the number of samples the motion blur
should use.
Axial Transparency—Astandardcircular
transparency gradient that affects the transparency
of the lens flare secondary elements along their
axis and relative to their source. This lets your
secondary elements 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 the final image. Use this
set of check b oxes 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 Scene—Specifieswhetherornotlensflaresthat
have their s ources 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 showi ng on
the screen. Without Off Scene, the lens flare does
notappearatall.Youcanturnthisoptiononoroff
for each p art of the flare.