gifOpenGL Tab

Bring up the Preferences window by selecting menu item ‘Edit’->‘Preferences’.

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This tab allows some OpenGL tweaks and work arounds for legacy graphics cards. The settings are are only applied after restarting the application.

Render Context

Multi-Sampling

OpenGL multi-sampling is turned ON by default because most graphics cards support it. However, you can turn it off on the ‘OpenGL’ tab of the Preferences Window.

IMPORTANT: If using Geodesica-SFX-MesaGL, (which uses software rendering), multi-sampling is turned OFF by default and can’t be changed.

Bit Depth

Note: some legacy graphics cards only support multi-sampling when the bit depth is set to 16; hence the bit depth is locked to this value. To change the bit depth, click the padlock icon to unlock it.

IMPORTANT: If using Geodesica-SFX-MesaGL, (which uses software rendering), the bit depth is set to 16 by default and can’t be changed.

IMPORTANT: If you change the bit depth and Geodesica fails to launch, or the OpenGL context fails to draw, or multi-sampling fails to work, you will have to reset the values manually by editing the ‘App.prefs’ file. This is stored inside Geodesica’s ‘Data’ folder. Follow these instructions carefully:

  1. Open the file ‘Data\Preferences\App.prefs’ in Wordpad.
  2. Find the section begining [./OPEN_GL]
  3. Change the bitdepth back to 16.

    BitDepth:16

  4. Change the MultiSampling value to a value supported by your graphics card. If in doubt, leave MultiSampling set to 0.

    MultiSampling:0

There are detailed instructions in [./OPEN_GL] section of the ‘App.prefs’ file. Eventually these will be command line options.

NOTE: Your graphics card driver might be configured to overide application settings in which case the OpenGL preferences will have no effect.

GL_POLYGON_MODE during Trackball and Camera Transformations

The settings in this panel allow you to override the current Attribute settings when rotating the scene (by dragging with the middle mouse button), or when moving the camera with the Navigator window.

When rotating the trackball or moving the camera, the GL_POLYGON_MODE for Cells, Hubs and Struts is changed to the settings on the OpenGL tab of the Preferences window. When the transformation completes and the mouse is released, the elements are redrawn according to the GL_POLYGON_MODE settings on the Attributes window.

This is especially useful when using the software renderer. If GL_FILL is used for struts and hubs on high frequency spheres, view transformations can slow to a crawl; but if GL_POINT is selected, only the vertices are drawn, which improves the frame rate.

In Geodesica-SFX-OpenGL the following defaults are used for trackball rotation:

Cells:  NO CHANGE
Struts: NO CHANGE
Hubs:   NO CHANGE

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Whilst in Geodesica-SFX-MesaGL the following defaults are used for trackball rotation:

Cells:  GL_LINE
Struts: GL_POINT
Hubs:   GL_POINT

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Note that when using GL_POINT for struts, only the vertices at the ends of each strut are drawn.