Before we talk about how to utilize the XNA Game
Studio graphic types to draw our first triangles on the screen, we need
to talk about one of the new changes that XNA Game Studio brings to
graphics.
Graphics Profiles Define Platform Capabilities
One of the large complexities has to do with how to handle
different graphics hardware on different platforms. Different graphics
cards support slightly different capabilities. This is especially a
problem on the PC where there are many different types of graphics
cards. In the past, developers had to query the graphics card for its
capabilities and then make decisions about what types of graphics
operations to use based on those stated capabilities. There were
hundreds of capabilities and they were difficult to test because you
needed all of the different types of graphics hardware accessible to
you.
To solve this problem, XNA Game Studio 4.0 introduced the concept of a GraphicsProfile.
A graphics profile sets specific requirements that a particular piece
of hardware meets or it doesn’t. If a particular piece of hardware
supports a profile, then all of the features in that profile are
supported. As a developer, you set the target GraphicsProfile. XNA Game Studio 4.0 supports two graphics profiles called Reach and HiDef.
When your application starts
on a machine that does not support every aspect of that profile, a
NoSuitableGraphicsDeviceException exception is thrown and enables you to
inform the user that he or she can’t run your game.
At development time, the graphics APIs in XNA Game Studio enforce the GraphicsProfile you selected. For example, the Reach profile supports textures with width and height up to 2048 while the HiDef profile supports up to 4096. If your game targets the Reach
profile, an exception is raised if you attempt to create a texture
larger than 2048 even if the PC you are developing on could support the HiDef profile. Having the APIs respect the GraphicsProfile setting ensures you do not use features that are not supported and your game runs on any platform that supports the Reach profile.
The Reach Profile
As the name implies, the Reach
profile provides the capability to give your game title reach meaning
that the code and content you create for your game would work on a large
number of platforms and systems. The Reach
profile is supported by Windows Phone 7 devices, the Xbox 360, and
Windows PCs with a DirectX 9 GPU that support shader model 2.0 or
higher.
The HiDef Profile
The HiDef
profile was designed for systems that provide more advanced graphics
capabilities. This limits the number of platforms and systems that
support the profile but allow for a richer set of capabilities. The HiDef profile is a superset of the Reach profile meaning that any platform and system that can support the HiDef profile by definition also supports the Reach profile. The HiDef profile is supported on the Xbox 360 and Windows PCs with a DirectX 10 or equivalent GPU.
So
what does equivalent mean? It means that some DirectX 9 hardware is
also supported but must meet some specific capabilities. The list of
capabilities is too long and of little importance to cover in this book.
Note
A chart comparing the
differences between the profiles including specific details such as
texture size limitations can be found in the appendix.
Determining GraphicsProfile Support
To find out whether your graphics card supports either of these two profiles, create a simple Windows application and call the GraphicsAdapter.IsProfileSupported method passing in a specific graphics profile.
