Graphics Programs Reference
In-Depth Information
Camera
Under the Renderable Cameras heading, you can choose the camera to render.
Image files are composed of red, green, and blue channels. Each channel specifies the
amount of the primary additive color (red, green, or blue, respectively) in the image.
(See Chapter 1 for more on how computers define
color.) In addition, some file formats can save a fourth
channel, called the
alpha channel
. This channel defines
the image's transparency level. Just as the red chan-
nel defines how much red is in an area of the image,
the alpha channel defines how transparent the image
is when layered or composited on another image. If
the alpha channel is black, the image is perfectly see-
through. If the alpha channel is white, the image is
opaque. The alpha channel is also known as the
matte
.
An object with a transparency will render with a gray
alpha channel, as shown in Figure 11.3.
The alpha channel can be displayed in the Render View window. As discussed later in
this chapter, your test renders also display in this window.
Figure 11.3
This wine bottle's
transparency ren-
ders with a gray
alpha channel.
To view an image's alpha channel in the Render View window, click the Display Alpha Channel
icon (
). To reset the view to RGB (full-color view), click the Display RGB Channels icon (
).
Most renders have the alpha channels selected, so leave the Alpha Channel (Mask)
check box checked at all times. Note, however, that JPEG, Graphics Interchange Format
(GIF), and Windows bitmap files don't support alpha channels, regardless of whether the
Alpha Channel (Mask) check box is checked as shown in Figure 11.4.
Only a few file formats, such as Maya IFF, support the depth channel. This grayscale chan-
nel resembles the alpha channel but conveys depth information: that is, the distance of an
object from the camera. The Depth Channel (Z Depth) setting is typically used when com-
positing images.
Figure 11.4
Output an alpha
channel.
Setting Resolution
The Width and Height attributes set the pixel size of the image to be rendered, a.k.a. the
image
resolution
. In the Image Size section of the Render Settings window, you can select
