This information is valid for PyMOL v1.4.0. Please see PyMOL Rendering Engine Improvements for later builds.
OpenGL shaders are a different way to render images. Instead of using the fixed pipeline of GL-based light models and effects, the lights and effects can be customized on the video card. This yields increases in rendering speed and allows for a great variety of effects.
PyMOL v1.4.0 and prior currently has shaders disabled by default. To turn on shaders
set use_shaders, 1# global shader setting
set cartoons_use_shader, 1# per representation setting
set sticks_use_shader, 1# per representation setting
set surface_use_shader, 1# per representation setting
set ribbon_use_shader, 1# per representation setting
set sphere_mode, 9(ARB) or
set sphere_mode, 5(GLSL)