glxinfo – show information about the GLX implementation

UNIX Command

$glxinfo | grep direct
direct rendering: Yes
    GL_EXT_Cg_shader, GL_EXT_depth_bounds_test, GL_EXT_direct_state_access,
$

UNIX Explanation

The glxinfo program shows information about the
OpenGL and GLX implementations running on a given X display.

http://www.opengl.org/documentation/

http://en.wikipedia.org/wiki/OpenGL