Celestia/Render Paths

Introduction

A Render path is Celestia's way of classifying graphics capabilities. Its different Render paths correspond to different sets of OpenGL functions.

Not all render paths may be available on your computer. A render path will be available only if your computer's graphics software includes the OpenGL functions that it uses. More sophisticated render paths require more recent graphics hardware, but not the most expensive version of a card.

When it is first started, Celestia automatically selects the best render path based on the graphics capabilities advertised by the computer's OpenGL library. However, you can interactively select any available render path. Celestia remembers which path you selected last and will use it when the program is restarted. Choosing another render path may be necessary if there are problems due to bugs in your computer's graphics drivers.

To select an alternate render path, type a Ctrl-V. That is, press the "V" key while holding down the "control" key. This causes Celestia to switch to the next available render path. The name of the newly selected render path will be shown briefly in the lower left hand part of Celestia's window.

Render Paths under Linux

see the windows it is THE SAME

Render Paths under MacOS X

Some of the render paths available on computers running MacOS X are

• Basic
• Multitexture
• DOT3+ARB VP
• NV C/VP
• NV C+ARB VP
• OpenGL 2.0

Render Paths under Windows

Some of the render paths available on computers running Windows are

• Basic
• Multitexture
• OpenGL Vertex Program
• OpenGL Vertex Program/Nvidia combiners (only on Nvidia graphics cards)
• OpenGL 2.0

Celestia can show more and improved "eye candy" when using the later render paths:

• Basic requires OpenGL v1.1.

It shows the fewest effects. It's available even on systems which have only Microsoft's software support for OpenGL and have no 3D hardware acceleration.

• Multitexture requires OpenGL v1.2.

It adds NightTextures and the shadow of a planet on its rings.

• OpenGL Vertex Program requires OpenGL v1.4.

It adds specular highlights on oceans, shaded mountainsides and the shadows of rings on a planet.

• Nvidia Combiners adds a rudimentary haze effect. (Only for Nvidia graphic cards)
• OpenGL 2.0 requires OpenGL v2.0.

It improves the edges of eclipse and ring shadows, draws the shadows cast by as many as four separate light sources, allows for point sprites, and adds sophisticated atmospheric effects, including cloud shadows on the ground. Haze can be drawn, too, based on Mie and Rayleigh scattering functions. (These scattering functions are available only with Celestia v1.5.0 or later.)

OpenGL Versions

To find out what version of OpenGL the graphics drivers on your computer claim to support, select Celestia's Help menu. The entry "OpenGL Info..." will list details about your computer's graphics hardware and software.