Professional Affair: OpenGL Graphics Cards Compete

Driver Direction For OpenGL Cards

One thing right at the beginning: If you think that buying an expensive OpenGL graphics card gives you a better performance for games, think again. Generally the graphics cards we tested are optimized for professional applications. Quake players still get a very good price/performance ratio with GeForce graphics cards and should not expect a significantly better performance from our test candidates. On top of that the manufacturers of the products tested below have very little interest in supporting Direct3D games. Accordingly there are not even any Direct 3D drivers for Windows 95/98 and 2000 available for the Diamond Fire GL 1 Pro and the Evans & Sutherland Lightning 1200. The main reason is the OpenGL API for applications and also the operating system architecture. Windows 95/98 does not support multiprocessor systems; for this you need NT 4.0 or the recently launched Windows 2000. Additionally many high-end applications do not run under Windows 95/98. However, even though it might not seem to make any sense from a theoretical point of view, there are quite a few practical reasons for the lack of support for Windows 9x.

1. Windows NT 4 and now Windows 2000 automatically offer a higher system stability, that reduces the support costs for graphic cards manufacturers to a bearable level.

2. Many midsize and large companies changed to Windows NT in the last two years.

3. NT 4 or Windows 2000 (formerly known under NT 5) allow the effective use of the so-called multi-threading. If there is another CPU present the computing processes can be distributed among the processors, increasing the overall performance.

The User Side

We interviewed a few companies that use professional OpenGL applications. We discovered a certain trend during the conversations: Contrary to 3D games, graphics projects hardly have a need for rendering large textures. Modeling of objects often only requires high polygon rates. As long as objects and scenes are still 'under construction', many designers are satisfied with displaying it in a wireframe model. And simple shading models are sufficient for viewing individual scenes during the production phase. A higher rendering performance is only necessary when the project enters the last stage. However, we were somewhat surprised when we heard that quite a few 3D scenes in the finishing phase are only rendered by the CPU and not by the graphics card. Many customers demand finished 3D animations in form of a movie presentation. The situation is different though, if the 3D scenes need to be interactive. These simulations follow the same rules as games: high fill rates combined with details requiring high polygon rates are a must. Because the user base is much wider in the OpenGL space than in the classic game environment, the cards are tested with a variety of application and synthetic benchmarks.

Geometry Engine And Rasterizer

If we look at the Evans & Sutherland Lightning 1200 and the two 3DLabs cards, we immediately notice the architectural differences to mainstream 3D cards. The three graphics cards use several graphics chips on the same board. In these products the graphics processors execute the stages of the OpenGL graphics pipeline separately. There also is a differentiation between the geometry engine and the rasterizer. Most of you are probably only familiar with the DirectX terminology from the 3D game world. Therefore we are going to explain the most important terms at this point.

Despite the different terminology the similarity between the Direct3D and the OpenGL pipeline is quite astounding. From a historical point of view the OpenGL API is older than the Direct3D API that is often used in games. But the Direct3D game API, formerly seen as a cheap solution, has come of age. Now it almost offers the same functions that OpenGL has had for years. Nevertheless, Direct3D was unable to conquer the workstation market despite the competitive functions. The main problem: Direct3D does not enable 3D hardware acceleration under NT 4.0. OpenGL, on the other hand, works on all Windows, Unix and Linux platforms. No wonder that programmers of workstation applications support the real standard OpenGL instead of Microsoft's proprietary Direct3D interface. OpenGL also simplifies porting applications to other platforms.

Both interfaces divide the necessary computing steps into two main areas: geometry and rasterization. The geometry stage converts the coordinate systems for a 3D scene, in relation to the position of the 3D objects in the room as well as the viewing angle (or 'camera position') of the user. If necessary, the effects of the light sources must also be calculated. What is simply called geometry in the OpenGL world was named transform and lighting under DirectX and Direct3D, respectively. There are two possibilities for geometry computations under OpenGL: Either the CPU of the workstation runs the calculations, or the computing-intensive steps are outsourced to a special graphics chip, the geometry engine. For quite some time now the OpenGL card manufacturers rely on these geometry engines to take load of the workstation CPU. In the game world under Direct3D this option has been available since the introduction of DirectX 7. Before that the CPU always had to do the task. Formerly nobody was very interested in geometry chips for mainstream cards because of the associated higher costs. This situation changed last year. With the GeForce Nvidia presented the first 3D game chip that integrates geometry and rasterizer on one chip. Shortly after a version for OpenGL cards followed: the Quadro. The latter is used by the company Elsa for the Gloria II.

AGP 2x, 4x And The Pro-Slot

For a few months now there has been an extension for the AGP slot in the true sense of the word. The suffix "Pro" indicates the extension. Both our test motherboards OR840 from Intel and the Asus K7V already have this extension. "Pro" stands for an additional power supply for AGP graphic cards and has nothing to do with the bandwidth of the bus. This extension became necessary because the number of transistors on high-end graphics chips has increased rapidly in the last years and with it also the power requirements. In mainstream graphics cards the standard AGP slot has been sufficient for supplying power to the graphics card up to now. With the 3Dlabs Oxygen GVX210 we saw the first product using the additional voltage supply of the Pro extension.

On the far right, next to the wide gap, are the connections for the additional voltage supply on the 3DLabs GVX210.

Here you see the AGP connection of the smaller brother of GVX210. The GVX1 works without Pro extension.

Can you make out the difference on the Elsa Gloria II? Exactly, the Pro extension is missing here as well, but you see the additional gap in the middle. This enables the transfer mode AGP 4X. All other OpenGL cards in this test are only capable of AGP 2X.

Uwe Scheffel