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choosing visuals

By default, Slithy requests an OpenGL visual with 8 bits per color channel, no alpha buffer, a 24-bit depth buffer, and an 8-bit stencil buffer. If it can't obtain this visual it will exit with an error message. You may need it to request a different visual, if you are on a machine which can't support the default, or if you are using an OpenGL diagram that requires an alpha buffer.

You specify the desired visual with a "visual string", which is six numbers separated by slashes:

red bits / green bits / blue bits / alpha bits / depth bits / stencil bits
Users of modest hardware might want to try "5/6/5/0/16/4", while those who need an alpha buffer might use "8/8/8/8/24/8".

Slithy looks for such a string in the following places, in order of preference:

  1. Given using the "-v" option when running any Slithy script.
  2. In the SLITHY_VISUAL environment variable.
  3. In the optional visual= argument to run_presentation() or test_objects().
  4. The built-in default, equivalent to "8/8/8/0/24/8".
If it is able to open a window, Slithy prints out the string for the visual it obtained (which might be deeper than what you actually requested).