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12 Chapter 1: Introduction to Computer Graphics and 3D
Raster Images
Raster images (a.k.a. bitmapped images) make up the world of computer images today. A
raster or bitmap image is a mosaic of pixels; an arrangement of colored pixels onscreen or
dots on a print to display an image. Everything you create in Maya will eventually be seen
as a raster image, even though you first create it using vectors.
Raster image programs, such as Photoshop, let you adjust existing settings such as
color, size, and position for all or part of an image. They let you paint onto a scanned
picture or a virtual canvas to adjust or create the pixels yourself. These programs affect
pixels directly, giving you the tools to change pixels to form images. For instance, you can
use a scanned photo of your house in Photoshop to paint the side of the house red to see
what it might look like before you run down to the local paint store.
The resolution of an image is defined by the number of pixels in the horizontal and
vertical directions. Because they’re based on a grid of a fixed size, raster images don’t
scale up well beyond a certain point. The closer you get to a raster image, the bigger the
pixels become, making the image look blocky, or pixelated. To make large raster images,
you need to begin with a higher resolution. The higher the resolution, the larger the file
size will be. Figure 1.3 shows what happens when you blow up a raster image.
Most common raster displays are television or computer screens. In fact, the term ras-
ter originally referred to the display area of a television or computer monitor. Every image
generated by a computer, therefore, must either begin as a raster image or be rasterized as
part of rendering for display.
Vector Images
Vector images are created in a completely different way. They’re formed using mathemat-
ical algorithms and geometric functions. Instead of defining the color of each and every
pixel in a grid of a raster image, a vector image uses coordinates and geometric formulas
to plot points that define areas, volumes, and shapes.
Popular vector-based image applications include Adobe Illustrator and Flash, as
well as practically all computer-aided design (CAD) programs, such as AutoCAD and
Figure 1.3
A raster image at its
original size (left)
and blown up sev-
eral times (right)
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