gravity = A 3D vector defining the force of gravity.
ambient_light = Ambient light level in the scene.
sun_direction = Direction of the sun's light.
fog_colour = Colour of the fog in the scene.
fog_density = How dense (thick) the fog is. High values indicate thicker fog.
mesh = Name of the mesh file for the scene.
mesh_path = Path to locate the scene's mesh file.
max_faces = Maximum number of faces that any given scene leaf can contain.
max_half_size = Maximum half size that any given scene leaf can be.
Note: A scene leaf will be divided if the total number of faces in the leaf is greater than max_faces and the size of the leaf divided by two (i.e. the leaf's "half size") is greater than max_half_size. Both conditions must evaluate to true for division to occur.