short:
create a separate black and white image the same dimensions as your map interface graphic, and fill the areas you want gone with black, and the areas you want visible with white.
go to the game options, apple + i, and find the map mask layout select your b/w mask.
extra:
transparent interface, preforation method:
build your mask as usual, in pure black and white.
go to apple works, open a paint document
in the menu, under format i believe, select 'document...' change the dimensions to that
of the mask.
fill the area with a pattern fill, black and white...same rules apply, the white will be visible the black masked out.
Use whatever paint app you have to cut away at the pattern fill to get it the shape of your mask, a wise move, if you have text or other things that you do not want "swiss cheesed up" mark their positions and place white versions of them into the mask image.
save the mask as pict.
...film method.
i've had varied sucess with using shades of grey, one thing is for certain, if you have a pure white mask and use a blur tool the grey will be properly interpretted and leave you with smooth edges, try it on a copy of the medieval map mask.
I believe that pure bodies of grey will be ignored and rendered black...somewhat the inverse of the way CGE currently treats png
( "...pure white will be masked out unless gradiated/stepped out into black...etc." )
so in keeping with that perhaps you could step out the white, giving elements a thin solid white border selecting them then executing a blend effect.
save as pict as well
etcetera etcetera etcetera.
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... bwahhaaaaahaaaaaugh fooooolish sammurai.
{ edit : added general random information to inspire the masses }
(This message has been edited by ellrx (edited 07-24-2003).)