Switches between 3d engines. Accepts d3d9, d3d11, gll or opengl as parameters.

Windows

Default

d3d9

DirectX 9.0c Memory management system 2.0

Possible Settings

opengl

Not recommended for Windows users except for testing purposes as it can cause WoW to crash itself

d3d11

New DirectX11 compatibility - only works with Vista (All updates required)/Windows 7, and DX10/DX11 graphics cards

Macintosh

Default

GLL

Rewrite of OpenGL, allowing for more graphics card usage, resulting in higher fps.

gxApi OpenGL/GLL (Updated for 3.3.3)... | 2010-02-09 23:37 | S4d1k

Requirements for GLL:

• Intel processor
• MacOS X 10.5.7 or later
• (Intel GMA 950 is not supported for now)

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Possible Settings

opengl

Recommended for most users

Patch changes

/ Patch 4.0.1 (12-Oct-2010):

• DirectX11 compatibility mode added - "d3d11"
• DirectX 9.0c functionality replaced with DirectX 9.0c Memory management system 2.0 (previously d3d9ex) 
  

Patch 3.3.3 (2010-03-23): Mac users default to "GLL" again after fixes to the engine. 
Patch 3.3.2 (2010-01-02): Mac users default back to "OpenGL". ^[1] 
Patch 3.3.0 (08-Dec-2009):

• New backend for Windows users added to the game engine. To enable, change this CVar to "d3d9ex".
• This CVar now defaults to "d3d9" from "direct3d" for Windows users.
• Mac users default changed to "GLL" from "OpenGL". 
  

Patch 3.2.0 (04-Aug-2009): New backend for Mac users to increase fps/better GPU usage as an alternate to "OpenGL" introduced. To enable, change this CVar to "GLL". 

References