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Celestia uses OpenGL graphics routines to draw its pictures of the universe. Unlike DirectX, which is available only on computers running Windows, OpenGL graphics libraries are available for many different types of operating systems. OpenGL was originally developed by SGI but now is available for use on almost all computers and graphics hardware. The OpenGL WikiBook has more details.
Celestia can run on most computers, but to see all of its "eye candy" a modern graphics card implementing OpenGL v2.0 is essential. Even when the best available graphic cards have been installed, some computers have problems running Celestia because their graphics drivers are out of date or buggy. Regularly check the Web site of the manufacturer of your computer or of your graphics card to make sure you have the current driver version. Updated drivers are provided often.
Graphics Card Limitations
Many graphics card limitations are described in Celestia's list of Frequently Asked Questions:
Operating System Limitations
Many computer and O/S limitations are described in Celestia's list of Frequently Asked Questions.
- OpenGL is distributed in many Linux flavors since is open source, but the graphic drivers not always are open source, thus, aren't included in all Linux distros.
Mac OS X
- Graphics driver updates for Mac OS X are available in updates to Mac OS X itself, not in general as separate driver updates by NVIDIA or ATI. This means "upgrade your driver" on OS X means "make sure your version of OS X is up-to-date". You may have to spend money in order to get the current version of OS X.
- Point sprite primitives do not work on versions of OS X earlier than 10.4.
- Point sprites are not supported properly on Tiger (PPC and Intel architectures). Colors may appear incorrect, and hard freezes requiring a reset have been seen. VBO seems to be involved. Apple has been made aware that this is almost certainly a driver bug, but no fixes have been promised. Behavior on Leopard is unknown.
- The OpenGL 2.0 render path is only supported on Tiger 10.4.3 or later, regardless of the graphics card.
Holes may appear in orbit paths on certain ATI configs. A workaround is being investigated.Fixed in 1.5.0.
- The graphics drivers provided with your brand new computer hardware already are obsolete. Usually several months have passed between the time its software was configured and it was provided to you. Be sure to download and install the most recent graphics drivers provided on the Web site of the manufacturer of your computer's graphics hardware.
- Windows XP includes a software-only OpenGL library. It's used on systems without 3D hardware or when hardware acceleration is disabled in the Display Control Panel. It implements only OpenGL v1.1, Celestia's Basic rendering path, so it has limited functionality and runs rather slowly, but it is relatively bug-free.
- Celestia does not use DirectX, which is Microsoft's proprietary 3D graphics programming library. Unfortunately, whenever Microsoft's DirectX libraries are updated, the manufacturer's OpenGL drivers are replaced by obsolete versions provided by Microsoft. Whenever you update DirectX, be sure to reinstall the graphics drivers using the most recent versions provided by the manufacturer of your computer's graphics hardware.