Feb 96 Enterprise Windows

3-D Graphics, OpenGL, NT

BY:by Martin Heller

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3D Graphics, OpenGL, NT

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3D Accelerator Board Vendors

Workstation graphics for NT: Accelerating OpenGL Love may make the world go 'round, but standards make the world of software go 'round.

Without standards in a given area, software developers find themselves constantly reinventing common functions.

With standards in place, not only can software developers concentrate on building useful applications, but hardware developers can build accelerators for these standards' common functions so that systems will run faster and be more useful.

What is OpenGL? The Windows API is a good example of a de facto standard controlled by a single company.

OpenGL, although it started out as a proprietary Silicon Graphics Inc. (SGI) 3-D graphics library, is now an open multiplatform 3-D graphics API standard controlled by the multivendor Architectural Review Board.

Windows NT is one of the major supported platforms for OpenGL; Windows 95 will support OpenGL shortly.

On the SGI platform, about 1,500 applications have been written to OpenGL; many of these apps either have been or are being ported to Windows NT.

GDI, the graphical portion of the Windows API, contains a rich set of two-dimensional primitive operations; OpenGL complements GDI with a rich set of 3-D modeling and rendering primitives.

Programmers use GDI to write code in terms of lines, curves and polygons drawn with pens and brushes of given colors.

Programmers employ OpenGL to write code in terms of solid and surface models with some material properties or textures, illuminated with a set of lights and viewed from a given camera position through an atmosphere that may include virtual fog.

Modeling and rendering of this sort are useful for design, simulation and CAD/CAMÑand also a boon to virtual reality.

Yes, indeed: OpenGL can even be used for entertainment, although it wasn't specifically designed for games.

Opening up OpenGL

The code for modeling and rendering scenes can take up quite a bit of CPU and display time.

OpenGL is speeded up significantly by good floating-point and display hardware.

What do we mean by "good"? Well, an SGI Indigo machine is "very good"; an Intergraph TDZ with dual Pentium Pro CPUs and a dedicated OpenGL accelerator with onboard Z-, frame-, alpha- and texture-buffering is even better; but a garden-variety 486 machine with a standard Super VGA card is not good.

Until recently, spending $20,000 on an Intergraph workstation, or considerably more on an SGI UNIX workstation, has been the most viable option for people who needed to do serious 3-D graphics work.

The big change recently is that chip vendor 3Dlabs has reduced most of the 3-D graphics rasterization functions required for OpenGLÑincluding hardware Gouraud shading, depth buffering, anti-aliasing and alpha blendingÑto a single chip, the GLINT 300SX, and developed an optimized OpenGL driver for this chip.

Several vendors now ship GLINT-based graphics boards; we've reviewed some in the table on the previous page and compared them to a good standard VGA card with 2-D acceleration.

The short summary: For a few thousand dollars, you can upgrade a Pentium-based computer to perform like a true 3-D workstation.

The proof of the pudding We compared GLINT-based Elsa GLoria and Omnicomp 3Demon cards with an S3 Vision 968-based Diamond Stealth 64 Video card running in a 100MHz Pentium-based computer. All three cards run in PCI bus slots, although it wasn't possible to put them in the same slot. We also tested a GLINT 300SX-based board and a more expensive DPI (Dynamic Pictures Inc.) card in an NEC RISCstation 2200, which is a 200MHz MIPS R4400-based workstation.

For comparison, the R4400 CPU benchmarks at 155MIPS and 71MFLOPS, while the Pentium CPU scores 178MIPS and 59MFLOPSÑin other words, the Pentium is better for integer computation, while the R4400 is the better choice for floating-point computation.

The GLoria is a full-length board that includes an S3-based VGA section as well as a GLINT-based section.

We had trouble fitting it into most of the PCI slots on our test computer because of interference from the CPU cooling fan; it did, however, fit easily into the last PCI slot.

The 3Demon, on the other hand, has no VGA section of its own; you must retain your old VGA card and use the supplied VGA pass-through connector cable, although the cable is short enough not to interfere with the CPU fan.

Because the Stealth card we used in this machine also attaches to the PCI bus, we needed two PCI slots to make the 3Demon work.

As you can see in the "Roller Coaster" through "Olympic Rings" columns in the table, all the 3-D graphics accelerator cards make dramatic improvements in the performance of OpenGL-based benchmark applications com- pared to the ordinary 2-D graphics accelerator, with speedup factors of between 2 and 10.

On the other hand, as you can see in the "NTHell Video" column, ordinary 2-D operations are not improved by some of these cards. Our informal applications tests bore this out.

You can visibly improve the rendering speed of OpenGL applications like MicroStation, Pro/Engineer and Design Review with these cards, but they make no perceptible difference in the performance of office applications.

While this review was done on Windows NT, Windows 95 users should be able to take advantage of 3-D acceleration technology very soon: OpenGL has been demonstrated running on Windows 95 with full acceleration on GLINT boards, and both the OpenGL libraries and GLINT drivers were scheduled to be available in January.

In addition, 3Dlabs and other 3-D accelerator vendors are actively supporting Microsoft's DirectDraw, Direct3D and Reality Lab APIs to provide graphics hardware acceleration to mainstream PC users running Windows 95.

These APIs are primarily designed for games, although it wouldn't be at all surprising if "serious" software vendors chose the Reality Lab APIs for some of their 3-D modeling and rendering needs.


Copyright 1995 CMP Publications Inc.