For model views, the mouse works in standard 3-button mode.
For view manipulation, editors do not recognize the middle mouse button. Instead, the mouse buttons are mapped as follows:
| Three button mouse | Two button mouse | One button mouse | 
|---|---|---|
|   |   |   | 
|   |  +   |  +   | 
|   |   |  +   | 
|  +  or  +   |  +   |  +  +   | 
This environment variable lets you change the opacity of pane menus. If you set the variable to 1, then the pane menus appear opaque. If you set the variable to 0 (zero) or leave it undefined, then the pane menus appear with Mac OS X default transparency. This variable does not affect the opacity of the main menus.

MAYA_MAC_SET_UMASK = 0