The model
The display of 3D images requires a series of
processes (usually referred to as a pipeline) and
then the translation of the results into 2D for
display on a monitor screen. An object is
first represented as a set of points, or
coordinates, in a 3D coordinate system. The 3D
coordinate system is defined by horizontal,
vertical, and depth axes, commonly known as the
x, y, z axes. An object may represent a house, a
person, car, plane, or complete 3D world, and the
coordinates define the position of the objects
vertices in space. Connect the coordinate
vertices with lines and the image becomes known
as a wire frame because, only the edges of the
shapes that form the object are visible. The wire
frame model bounds surface areas that can be
filled with color, texture, and upon which light
can shine. 
Figure 1: Wireframe model of a cube
Even with such a simple explanation of a 3D graphics pipeline
it is obvious that many calculations must occur
in order to render a 3D object onto a 2D display.
Imagine how much more calculation has to be done
with the coordinate system when an object moves.
Figure 2: Shaded model of a fighter jet
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The role of the API
Applications Programming Interfaces (APIs) exist
that handle the functions of the 3D pipeline in
software only, but can take advantage of 3D
hardware where it exists. If hardware
acceleration is there the API uses its features,
but if no acceleration exists, the API has been
optimized to run on the most common systems. So
any number of software programs can be supported
by any number of hardware accelerators for 3D,
providing they use some API. Entertainment
software is supported by Microsoft’s
Direct3D, Criterion’s Renderware,
Argonaut’s BRender, and Intel’s 3DR, to
name but four. Apple have entered the fray with
Rave based on their Quickdraw 3D API. For
professional applications, OpenGL dominates and
runs under Windows NT. SoftImage, a popular
animation and 3D design application running on
Silicon Graphics workstations, is spearheading
the migration of many high-end workstation
applications to Windows NT based PCs. Autodesk,
the largest maker of computer aided design
software, has developed its own API, called
Heidi.
The availability of 3D APIs
that can support many graphics subsystems, and
many applications, is increasing the demand for
real time 3D hardware acceleration. Entertainment
is a major driving force on the PC, but Windows
NT based applications, that have migrated to the
PC from high end workstations, are also fueling
the development of very powerful graphics
subsystems for professional 3D graphics.
Applications on the internet are set to benefit
from the greater maneuverability that a 3D
interface would provide. After all, it is the
world wide web which has been the biggest
proponent of virtual communities on-line. These
communities may be much easier to access if they
can exist in a 3D universe.
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