Video Hardware - Upgrading and Repairing PCs - page 800

Using these elements, the abstract image descriptions must then be rendered, meaning
they are converted to visible form. Rendering depends on two standardized functions that
converttheabstractionsintothecompletedimagethatisdisplayedonscreen.Thestandard
functions performed in rendering are as follows:
• Geometry —The sizing, orienting, and moving of primitives in space and the calcula-
tion of the effects produced by the virtual light sources that illuminate the image
• Rasterization —The converting of primitives into pixels on the video display by
filling the shapes with properly illuminated shading, textures, or a combination of the
two
A modern video adapter that includes a chipset capable of 3D video acceleration has spe-
cial built-in hardware that can perform the rasterization process much more quickly than
if it were done by software (using the system processor) alone. Most chipsets with 3D ac-
celeration perform the following rasterization functions right on the adapter:
• Scan conversion —The determination of which onscreen pixels fall into the space de-
lineated by each primitive
• Shading —The process of filling pixels with smoothly flowing color using the flat or
Gouraud shading technique
• Texture mapping —The process of filling pixels with images derived from a 2D
sample picture or surface image
• Visible surface determination —The identification of which pixels in a scene are ob-
scured by other objects closer to the viewer in three-dimensional space
• Animation —The process of switching rapidly and cleanly to successive frames of
motion sequences
• Antialiasing —Theprocessofadjustingcolorboundariestosmoothedgesonrendered
objects
Note
Tolearn moreabout3Dtechniques suchasfogging,Z-buffering,T-buffering,programmable
shading, and rendering methods, see the sections “Typical 3D Techniques,” “Advanced 3D
Filtering and Rendering,” and “Single-Versus Multi-Pass Rendering,” in Chapter 12 , “ Video
Hardware ,”in Upgrading and Repairing PCs, 19 th edition ,includedinitsentiretyonthedisc
packaged with this topic.
Software Optimization
It's important to realize that the presence of an advanced 3D-rendering feature on any
given video card is meaningless unless game and application software designers optimize