(^272) PC Hardware: A Beginner’s Guide
Rendering
The final step in the preparation phases for a 3D display is the rendering phase. The pre-
vious phases have defined the image to be included in a video frame, how it is to be
lighted, how this image is represented in terms of three-dimensional geometry, and fi-
nally, how it can be created as a series of triangles that construct the form of the image.
The rendering phase finishes the process by assigning color, texture, lighting, transpar-
ency, fog, and other treatments to each row of pixels that makes up each triangle that has
been rendered (drawn). After each row of pixels in each triangle of the image frame has been
assigned its values, the image is fully rendered.Fill Rate
The rendering process draws the frame using the instructions generated by each of the
previousphases.Howfastthishappensisbasedonthevideocard’sfillrate,orhowmany
pixels or texels (the triangles used to create texture on the screen) can be rendered per sec-
ond. The fill rate may be the most important performance indicator of a 3D video card. A
card can have a fire-breathing 3D pipeline that is quenched by a slow fill rate.Rendering Activities
The rendering process includes a variety of filtering and texturing processes that are used
to create the effect desired in each frame: Anisotropic Filtering One of the more advanced texturing techniques,
in which 16 texels are used to form the texture map of each polygon.
Antialiasing A technique used to reduce the “noise” added to the image when
all of the graphic information is not available. The information about an image
should include its position, colors, size change, and more, but if it is not available,
the missing factors are filled in with what is called noise. Antialiasing attempts
to remove this noise.
Bilinear filtering A standard texturing method on virtually all 3D graphic cards
that reads four texels, calculates the averages of their positions, colors, and other
properties, and displays the result as a single-screen texel. This technique is used
to reduce blockiness in the display and has a blurring effect on objects as they
approach the viewer.
Bump mapping This technique is used in place of embossing to create the
illusion of depth or height on a textured surface. This is the process used to
create rough roads, bomb craters, and bullet holes on walls.
Filtering This process smoothes the textures applied to blend, or slightly
blur, the colors of adjacent pixels to eliminate a blocky look.
Mip mapping This technique improves the appearance of textures by
grouping pixels into mip-maps that cluster four texels together to remove
jagged edges between pixels and texels. The termmipstands for the Latin
phrasemultum in parvoI,which means multitude in a small place.