User manual HP COMPAQ PROFESSIONAL XP1000 GRAPHICS: THE WORKSTATION DIFFERENCE

[. . . ] Technology Brief April 1999 0054-0499-A Prepared by Workstation Division Compaq Computer Corporation Graphics: The Workstation Difference Abstract: Graphics are the most visible and most critical part of workstations. Focusing on 3D graphics, this paper explores the role and importance of graphics and recommends graphics products for specific needs. A discussion of graphics implementation issues is included, which examines when graphics operations make sense to implement in hardware and which should remain in software. Finally, key graphics interfaces -- both software and hardware -- are explored. [. . . ] Regularity measures the amount of variation or choice in an algorithm. Some algorithms are extremely regular -- the previously mentioned pixel write requires no choices and has no variations, and the Z-buffer algorithm requires a single comparison and choice. But the manipulation of application objects like models involves extreme variation and, thus provides very little regularity. An example of a graphics operation that can vary in both complexity and regularity is lighting. Some lighting, such as ambient or simple directional light, is relatively simple. These two lighting models can be placed in hardware fairly easily. On the other hand, lights can be directional, have "barn doors" (controls that allow screening the light, much like the flaps on professional theater lights), fall off with distance, have color, cast shadows, and other even more complex functions. These lighting models are extremely complex, very irregular, and very difficult to put into hardware. They are invariably done in software. - Data Traversal - Object Operations - Lighting - Texturing Complexity - Transformation - Span Generation - Span Interpolation - Z-buffer, Pixel Write Regularity Figure 2: Complexity vs. Regularity 0054-0499-A Graphics: The Workstation Difference 7 Figure 2 shows the complexity and regularity of several key graphics operations. They range from simple, regular operations such as pixel write and Z-buffer operations, through a set of operations with increasing complexity and decreasing regularity. This chart also shows operations can increase in complexity without decreasing in regularity; this is an important point, as these operations can be efficiently accelerated in hardware. PowerStorm graphics integrate hardware and software components supporting a broad range of hardware graphics accelerators through a common interface. This insulates applications from underlying hardware, and allows you to make graphics purchasing decisions based upon performance requirements rather than arbitrary combinations of "which graphics hardware goes on which workstation platform and supports which applications. " OpenGL OpenGL is quite simple in many ways. It can be described as a programming interface for three dimensional graphics, much like Direct3D, PHIGS or a number of proprietary interfaces. But it is also much more than that -- it is hardware, operating system, and window system independent. OpenGL is available from dozens of computer companies. It is a standard part of Microsoft' s Windows NT, and is supported on virtually all versions of UNIX. OpenGL is the 3D interface for graphics hardware ranging from a simple 8-bit frame buffer to ultra high end graphics subsystems costing several hundreds of thousands of dollars. There are several key aspects to OpenGL. Unlike some standards that were developed in committees, OpenGL was developed to support applications development. OpenGL has evolved and proven itself as an interface that meets the needs of software developers. [. . . ] AGP 2X and 4X retain the 66 MHz bus of AGP 1X, but allow multiple data transfers on a single bus clock cycle. AGP 4X allows four data transfers on each clock cycle. 0054-0499-A Graphics: The Workstation Difference 10 The implementation of AGP as a point to point bus enables much of AGP's performance. By eliminating multiple devices on the bus, signal integrity problems are greatly reduced and bus clock rates can be increased. Likewise, eliminating the need to determine which of several devices has control of the bus simplifies the software interface and improves performance there. [. . . ]