For years we asked the same questions when doing support where video issues were concerned. Is your video card OpenGL? Is it certified for use with your CAD software? What version of the driver are you using? Do the artifacts occur when you move the mouse from left to right or right to left? How much RAM is on the video card? The reason for all these questions was simple: Everything had to be a perfect match to get the performance you wanted and not have unexpected results. The old standard was that OpenGL was for professional workstations and most others were for general office use or were a dreaded “gaming card.” Now the water is murky, if not muddy, thanks to Windows Vista.

Gaming Card vs. Professional Workstation Graphics
While both card types produce graphics, they performed the functions in very different ways. One used rendered polygons and the other used ray-tracing to produce images. One was great for high-speed animation and the other was for accuracy. And such was the way of the world. With Windows Vista, Microsoft changed that for PC users. OpenGL was no longer directly supported by a driver in Windows Vista, but was instead funneled or translated through a driver using Direct3D. With some cards, this resulted in poor performance. CAD manufacturers therefore began to have drivers for Direct3D video cards. Suddenly high end gaming cards found a new home in the professional workstation.

SGI's OpenGL
SGI's (Silicon Graphics) OpenGL is a procedural 3D graphics API, the successor to Iris GL which originated in the UNIX workstation market. Many of you will remember we sold those SGI stations along with those from HP, Sun and IBM. The Iris GL is the graphics API used on a succession of 3D graphics workstations designed and built by Silicon Graphics, Inc. Many of the OpenGL cards for PCs were based on this chip set. "OpenGL" is a trademark of the OpenGL Architectural Review Board (ARB). The ARB controls the definition of OpenGL through control of the specification by which an implementation may call itself "OpenGL." By definition, OpenGL is a graphics state that controls the rendering pipeline.

Microsoft's Direct3D
Microsoft's Direct3D is a COM-based 3D graphics API originating in a third-party 3D graphics API for x86 architectures. As with many components of Microsoft’s products, DirectX was acquired in 1996. Direct3D contains an immediate-mode interface and is part of DirectX. As it evolved, first appearing in DirectX 3, Microsoft Direct3D used execute buffers as its display structure. Since DirectX 5, a more traditional approach to buffers and primitives has been adopted with each successive version.

Feature Comparison
So what is the real difference? OpenGL and Direct3D use a traditional graphics rendering flow or pipeline. The use of a “pipeline” format has been present since the earliest days of computer graphics and has been enhanced and extended to use faster interfaces and the addition of plentiful RAM as technology advances. Of all the information I found, this chart shows the comparisons between the two formats and how they differ: