I'm not sure as if it's called doodads or decorations, but I'm having problem with this.
The doodad I'm trying to use is a big xelnaga-green glass floor that comes out in LoTV campaign 'Temple of Unification'.
This floor-like doodad is transparent that it's mechanic doodad animations beneath is visible.
Now the problem is that if I decrease the height of the terrain, this place would be impossible to pass through. If I just simply put this doodad on my normal terrain, the doodad animations beneath this glass floor is not shown.
Is there a good way to solve this problem? (Sorry for the poor information, I don't know where to upload my image, how to put url..)
What you can do is decrease the terrain cliff to show the mechanical animation underneath, use the "InvisiblePlatform16x16" doodad and place it where the glass is. Use the height modification tool and make the invisible platform level with the ground that you want units to walk on. Then go to the Pathing tab and cover the glass with the GREEN "pathable" brush. That will allow units to walk on the glass without them colliding with the cliffs. The invisible platform will keep the units level and prevent the from falling through the glass...