Ever spent hours trying to line up tunnels on the z axis. Ever had stacked walls that over lap so bad that when you see them your eyes want to bleed. Ever tried to line up bridges and encountered a speed bump along the width. Well Absolute Height is the quick and easy answer to these problems and more.
With AH, you can adjust all the z axis in a group of objects all at one time without having to take in consideration the diverse changes in landscape in a matter of seconds.
In other words turn this...
into this...
or this...
into this...
But what is Absolute height you're asking.
Absolute height is the distance above the base of the terrain. In other the words, if you dig a hole in your terrain, it can only go down so far. Because, unlike the real world being a sphere, the LW world is flat. So it has a bottom at Absolute height of 0. Nothing can be done below this level. When you place an object in the MED it defaults to 0 Z of the terrain which is piles of "dirt" on top of the base.
Now how to apply this knowledge.
First thing to do is make sure you have all the objects aligned properly in the x and y axis.(see FAQ #3)
Then you need to determine what absolute height the objects need to be at. To do this for bridges, select the one you think is closest to being positioned correctly to begin with. (In the pictures above I used the one on the far right).
Select it on your MED by clicking on it.
Then open the "Item attributes" window. In the upper left you should see something like this.
Notice the Z is at 0. So it's sitting level with the ground.
Now click the Absolute Height box and it will change to something like this.
Now the Z shows the height above the base of the whole 3D world. In this example it's 106/152 or 106.59432m above the base.
Make a note of the height shown in the Z box and uncheck the absolute height box.
Next select the rest of your objects so they are all yellow in the MED work window.
Reopen the "Item Attributes" window.
(The next few steps are done so that you set them all to one height and then moves them to the proper height. It takes into consideration that the absolute height system tends to act buggy at times. So I've added a few extra steps that will eliminate the problems that can arise from using it. Once you've used it a few times you'll understand how it works and can disregard some of the steps.)
Check the absolute height box and set the Z value to 1.
Uncheck the absolute height box and click OK
Reopen the "Item Attributes" window.
Check the absolute height box and set the Z value to the proper height (like in the example 106/152).
Uncheck the absolute height box and click OK
Whala your Done. All the objects will now be set evenly to the same height.
As far as tunnels go, they are done the same way except the reference height comes from the tunnel entrance. You have to get the absolute height of the entrance and subtract 5 or 8 from it depending on the type of entrance it is. So if the absolute height of the entrance is 106/000 your tunnel will be either 101/000 or 98/000.