perspective
Controls which projection is applied by default when creating 
a new layer. When 
perspective is set to 
no, an
orthographic projection is applied.
Example: <layer perspective="yes"/> (default)
(defined in GAMGI_MESA_LAYER_PERSPECTIVE)
Allowed values: yes, no (optional)
near, far, top
Set the projection volume dimensions that are applied by default, when creating 
a new layer. 
near and 
near mark the minimum and maximum distance 
from the observer for objects to be visible. 
near must be smaller than 
far.
Example: <layer near="1.0" far="1000.0" top="0.5"/> (default)
(defined in GAMGI_MESA_LAYER_NEAR, GAMGI_MESA_LAYER_FAR 
and GAMGI_MESA_LAYER_TOP)
Allowed values: positive real (optional)