Video Hardware - Upgrading and Repairing PCs - page 799

ics. Many cards in the $50-$150 range use lower-performance variants of current high-
end GPUs, or they might use the previous year's leading GPU. These cards typically
provide more-than-adequate performance for 2D business applications. Most current 3D
accelerators also support dual-display and TV-out capabilities, enabling you to work and
play at the same time.
However, keep in mind that the more you spend on a 3D accelerator card, the greater the
onboard memory and faster the accelerator chip you can enjoy. If money is no object, you
can buy a graphics card featuring its fastest GPU for more than $500. Fortunately, there
are plenty of choices using either NVIDIA or AMD GPUs in the less than $500 price
rangethatofferplentyof3Dgamingperformance,includingsupportfordual-GPUopera-
tions (NVIDIA SLI or AMD CrossFire X), which split rendering chores across the GPUs
in both video cards for faster game display than with a single card. GPUs that support
DirectX 10/11 are the preferred choice for anyone who wants to play current generation
games.
Mid-range cards costing $100-$300 are often based on GPUs that use designs similar to
the high-end products but might have slower memory and core clock speeds or a smaller
number of rendering pipelines. These cards provide a good middle ground for users who
play games fairly often but can't cost-justify high-end cards.
The basic function of 3D software is to convert image abstractions into the fully realized
images that are then displayed on the monitor. The image abstractions typically consist of
the following elements:
• Vertices —Locationsofobjectsinthree-dimensional space,describedintermsoftheir
x, y, and z coordinates on three axes representing height, width, and depth.
• Primitives —The simple geometric objects the application uses to create more com-
plex constructions, described in terms of the relative locations of their vertices. This
servesnotonlytospecifythelocationoftheobjectinthe2Dimage,butalsotoprovide
perspective because the three axes can define any location in three-dimensional space.
• Textures —Two-dimensional bitmap images or surfaces designed to be mapped onto
primitives. The software enhances the 3D effect by modifying the appearance of the
textures, depending on the location and attitude of the primitive. This process is called
perspective correction . Some applications use another process, called MIP mapping ,
that uses different versions of the same texture containing varying amounts of detail,
depending on how close the object is to the viewer in the three-dimensional space.
Another technique, called depth cueing , reduces the color and intensity of an object's
fill as the object moves farther away from the viewer.