Grass Valley Xstudio Vertigo Suite v.4.10 - Manual (Page 141)

6-28 Xstudio User Manual
Working with scene objects
Using scene objects as a mask
When scene objects are layered on top of each other, the top object can be defined as a
mask. Using the mask’s alpha defined areas to reveal or block areas of the object behind
it. Masks allow you to create impressive graphical effects by creating soft fades, decorative
edges, and translucent effects.
Any object on the scene that has an alpha (image, cel, clips, text... etc.) is able to mask an
object behind it. This means that masks can be irregular shaped since they are based on
the exact shape of the mask object’s alpha areas.
N OTE
If the objects have been grouped, you can use the entire group as a mask by setting the group’s
Mask properties. See
“Group object properties” on page 15-40 for more information.
To specify that an object is to be used as a mask, you must set the U SE A S M ASK parameter
in the object’s Xstudio properties. The following values are available for the U SE A S M ASK
parameter:
•
N ONE : Disables masking. In other words, the object will not be applied to the scene as
a mask.
• P OSITIVE : Enables the object as a mask on the scene by displaying the lower image
where the mask object’s alpha value is 1. In areas where the object’s alpha value is 0,
the masked object (lower) is hidden (blocks the lower image).
• N EGATIVE : Enables the object as a mask on the scene by displaying the lower image
where mask object’s alpha value is 0. In areas where the object’s alpha value is 1, the
masked object (lower) is hidden (blocks the lower image).
Figure 6-4 shows a scene where two of the three objects are grouped so that part of logo
(back) will be masked by a white polka-dotted image (front). The white dots in the mask
image have an alpha value of 1 and the transparent area has an alpha value of 0. When the
dots image’s U
SE A S M ASK parameter is set to P OSITIVE and the scene is played out, the
white area (holes) reveal the logo image behind it. In the area where the alpha value is 0,
the logo is not shown (blocked), but the background is displayed since it was not part of the
group being masked.
Figure 6-4. Masking one object with another
Scene in Xstudio Playout