Quote Originally Posted by Alecthar View Post
What's the most efficient way to do that in Gimp? I'm pretty unsure exactly how to wield the "Drop Shadow" filter.
Make a selection that has just the walls outline shape on it. I usually turn off all the other layers except the one with the walls shape. Take this selection and invert it (so that the selected parts are the "walls" interior. Now you wan to grow(or shrink) the selection (see the selection menu in GIMP) so that the selection is slightly bigger than the original(if you turn the grey walls back on, the selection should be out in the rooms by a few (2-5) px instead of inside any of the walls. Fill with black. Move the layer to below the walls and above the floor texture. Turn off the selection and use G. Blur to suit. Probably 5 px, perhaps 10. This depends on how much bigger the selection was that you filled with black.