Dry
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A Zone controls ambient lighting and fogging. Each geometry object determines the zone it is inside (by testing against the zone's oriented bounding box) and uses that zone's ambient light color, fog color and fog start/end distance for rendering. For the case of multiple overlapping zones, zones also have an integer priority value, and objects will choose the highest priority zone they touch.
The viewport will be initially cleared to the fog color of the zone found at the camera's far clip distance. If no zone is found either for the far clip or an object, a default zone with black ambient and fog color will be used.
Zones have three special flags: height fog mode, override mode and ambient gradient.
Like lights, zones also define a lightmask and a shadowmask (with all bits set by default.) An object's final lightmask for light culling is determined by ANDing the object lightmask and the zone lightmask. The final shadowmask is also calculated in the same way.
Finally, zones can optionally define a texture, see SetZoneTexture(). This should be either a cube or 3D texture that will be bound to the zone texture unit (TU_ZONE) when rendering objects within the zone. This could be used to achieve for example precomputed environment reflections, ambient lighting or ambient occlusion in custom shaders; the default shaders do not use this texture. Due to texture unit limitations it is not available on OpenGL ES 2.0.