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Table Of Contents
Light Wrap is the last operation in the image-processing pipeline. In other words, the
light-wrap effect is added after every other image operation is processed, including filters,
lights and shading, and other composited effects. As a result, Light Wrap accounts for
any visual effect that might alter the look of the object it is applied to, yielding the most
desirable result.
Important: A separate Light Wrap option appears in the Blend Mode pop-up menu of
the Properties Inspector for a selected layer or group in Motion. The Light Wrap blend
mode in the Properties Inspector for a layer is ignored when you add a Keyer filter to that
layer and set the Light Wrap Amount parameter to a value greater then 0. (The Light
Wrap parameters of the Keyer filter take precedence.) However, if you set the Amount
parameter of the Light Wrap group to 0, the Light Wrap blend mode becomes active
again. Further, the Light Wrap blend mode in the Properties Inspector for a group overrides
the Light Wrap parameters of any Keyer filters in that group.
Amount: Use this slider to control the light-wrap effect, setting how far into the
foreground the light wrap extends.
Intensity: Use this slider to adjust gamma levels to lighten or darken the interaction of
wrapped edge values with the keyed foreground subject.
Opacity: Use this slider to fade the light wrap effect up or down.
Mode: Use this pop-up menu to choose the compositing method to blend the sampled
background values with the edges of the keyed subject. There are five modes:
Normal: Evenly blends light and dark values from the background layer with the
edges of the keyed foreground layer.
Lighten: Compares overlapping pixels from the foreground and background layers,
then preserves the lighter of the two. Good for creating a selective light wrap effect.
Screen: Superimposes lighter portions of the background layer over wrapped areas
of the keyed foreground layer. Good for creating an aggressive light wrap effect.
Overlay: Combines the background layer with the wrapped areas of the keyed
foreground layer so overlapping dark portions become darker, light portions become
lighter, and colors become intensified.
Hard Light: Acts like the Overlay composite mode, except that colors become muted.
Preserve RGB: Select this checkbox to preserve smooth graphics and text. Some images
may be rendered as if they have an alpha channel, even though they don’t. A good
example is white text on a black background. Rasterized text in most images is antialiased
properly, and further modification to the RGB channels by the Luma Keyer can degrade
the quality of the edges. Selecting the Preserve RGB checkbox adds transparency to the
image without modifying the RGB channels, leaving smoothly aliased text or graphics
visually intact.
663Chapter 13 Keying