Hardware Reference
In-Depth Information
OpenGL and Direct3D are available for virtually all leading graphics cards. At one time, a third
popular game API was Glide, an enhanced version of OpenGL that is restricted to graphics cards that
use 3dfx chipsets, which are no longer on the market.
OpenGL
The latest version of OpenGL is version 4.2, released on August 8, 2011. OpenGL 4.2 is based on
OpenGL 4.1, which has the following improvements over OpenGL 3.x:
• 64-bit double-precision floating point support
• New shader stages and subroutines for faster and better quality of 3D rendering
• Better performance compared with the previous OpenGL 3.x versions
OpenGL 4.2 adds the following features:
• Support for shaders with atomic counters and load/store/atomic read-modify-write operations
to a single level of a texture
• Capturing GPU-tessellated geometry and drawing multiple instances of the result of a transform
feedback to enable complex objects to be efficiently repositioned and replicated
• Support for modifying an arbitrary subset of a compressed texture, without having to re-
download the whole texture to the GPU for significant performance improvements
The following GPUs include OpenGL 4.2 support: NVIDIA GeForce 400 series, NVIDIA GeForce
500 series, NVIDIA GeForce 600 series, ATI Radeon HD 5000 series, AMD Radeon HD 6000
Series, and AMD Radeon HD 7000 Series.
OpenGL 4.x is backwards compatible with OpenGL 3.x.
Although OpenGL is a popular gaming API, it is also widely used in 3D rendering for specialized
business applications, including mapping, life sciences, and other fields. Windows XP and newer can
support OpenGL either through software or through hardware acceleration. For a particular graphics
card to support hardware acceleration of OpenGL, the driver developer must include an installable
client driver (ICD). The ICD is distributed as part of the driver package that the video card or GPU
vendor provides. Thus, driver updates can improve OpenGL performance as well as DirectX
(Direct3D) performance.
To learn more about OpenGL, see the OpenGL website at
www.opengl.org
.
Microsoft DirectX
Direct3D is part of Microsoft's comprehensive multimedia API, DirectX. Although the most recent
versions of DirectX (9.0c and up) provide support for higher-order surfaces (converting 3D surfaces
into curves), vertex shaders, and pixel shaders, significant differences exist between DirectX
versions in how these operations are performed.
DirectX 9.0c uses separate pixel and vertex shaders to create 3D objects. Although DirectX 9.0c
provides greater precision in data handling as well as support for more instructions, more textures,
and more registers than its predecessors, its use of separate shaders can still lead to slow 3D
rendering when more pixels must be rendered than shaders, or vice versa. Shader Model 3 (used by
DirectX 9.0c) is simply a development of the split-function design first developed for Shader Model
1 (used by DirectX 8.0) back in 2001, adding support for more instructions and greater numerical
accuracy.
DirectX 10, developed for Windows Vista, includes a completely rebuilt Direct3D rendering engine
