quickstart THE BEGINNING OF THE MAGAZINE, WHERE ARTICLES ARE SMALL
08 MA XIMUMPC SEPTEMBER 2006
B
ackward-compatibility is the bane
of many a programmer’s existence.
Creating software that’s capable of running
on hardware that’s fi ve or more years old
can lead to a creaky, cranky, unstable prod-
uct; backward-compatibility is also one of
the biggest causes of code bloat. So for the
fi rst time in the history of DirectX, Microsoft
is rebuilding its infamous collection of APIs
and streamlining them into one all-inclu-
sive package. According to Microsoft, the
result is a DirectX that’s faster, contains
less resource-hogging overhead, and will
enable developers to create visual andother effects that have never before been
possible on the PC. But this power car-
ries a price: DirectX 10 will be integrated
into Windows Vista only (the new OS will
also include DirectX 9), and none of the
current-generation GPUs are DirectX 10-
compatible, so you’ll have to upgrade your
hardware to get DX10 support.
Most of DirectX 10’s advancements
are on the graphics side, and include the
brand-new Shader Model 4.0. In addition to
its heavily revamped pixel and vertex shad-
ers, Shader Model 4.0 will sport an all-new
geometry shader that sits between the other
two shaders in the Direct3D pipeline.
The geometry shader accepts the output
from the vertex shader, in the form of a sin-
gle vertex (a point, line segment, or triangle),
and affi xes additional attributes to it—a
realistic shadow, for instance. The geometry
shader can also be programmed to create
additional geometry by multiplying a single
vertex and then outputting multiple copies,
each with different attributes. These new
features should enable developers to endow
their games with fl owing cloth and more
realistic fog, without hampering speed.
One feature that won’t be included
in DirectX 10—at least not at its initial
release—is a physics API. “We are work-ing with the companies that currently make
physics engines,” said Chris Donahue,
Microsoft’s director of business develop-
ment for Games for Windows, “but we have
nothing to announce at this time.”THE UNITY PLEDGE
In DirectX 9’s graphics pipeline, vertex-
and pixel-shader processing is handled
by discrete units inside the GPU. The
drawback to this design is that if the GPU
becomes bogged down performing pixel-
shader operations, the vertex-shader
units could be left twiddling their thumbs
until the pipeline is cleared. DirectX 10
seeks to eliminate this problem by sup-
porting a unified architecture in which a
single engine is capable of performing any
shader operation: pixel, vertex, or geom-
etry; whatever is needed at the moment.
A component onboard the GPU, known as
the “thread arbiter,” will ultimately decide
each shader unit’s task.
This aspect of DirectX 10 is similar—
philosophically, at least—to the Xbox 360’s
graphics architecture, which should make it
easier for game developers to write games
for one platform and then easily port them
over to the other.Get Ready for Direct X 10
Microsoft is throwing the
baby out with the bath
water—and that’s a good
thing when it comes to
DirectX, because the new
version looks to be lean,
mean, and clean
From the land of sky-blue waters: The screenshot on the left was taken from Microsoft’s upcoming Flight Simulator X running un-
der DirectX 9; the image on the right is a Microsoft artist’s rendering of how the tenth anniversary game will look—theoretically, at
least—running on DirextX 10.