Z-Axis
Z-axis is one of the key Map Design. In mathematics, z-axis in the vertical axis in a 
Cartesian coordinate system – in FPS games , it refers to the use of height.
The use of height can dramatically change the way a map flows, for good or ill. Vast drops into chasms and lakes of lava will put people off those routes (and possibly the map) especially if the bridges are easy to fall from. Being able to drop into position directly behind someone from a ledge can add an element of strategy and suprise to a map that would otherwise be missing. The other thing adding the magic z dimension to your map can do is make it appear much large than it actually is. Adding a level or two to a map can increase the perceived size of the level without actually making the dimensions of the map much larger. This means the action is not slowed down as much as it would be if the map had simply been enlarged.
Gametype Sections
Here are some sections (slightly re-worded) taken from other parts of the wiki on map creation for the various gametypes.
Domination
A good Domination map should at least have two, but preferably three, different height levels. For an example of good z-axis usage, check out DOM-Olden. The map has a good, open structure with wooden beams at a lot of different levels. It encourages the player to use his/her translocator more and it improves gameplay a lot, because attacks can come from anywhere. DOM-Gearbolt also has some suprising z-axis play due to the fixtures just below the roof and the placement of the bridge.
Double Domination
The use of the z-axis in Double Domination maps is a much more controlled affair than in UT's Domination. Double Domination revolves entirely around controlling two points for the given amount of time. This means that z-axis use should primarily be used to aid control point defense. Remember also that there is no translocator in Double Domination so players will have to use map features (lifts, ramps, kickers) to travel between the levels of the map.
Deathmatch
When building a good Deathmatch map the z-axis is essentially part of your flow. Being able to go up and down easily allows more complex strategies to be adopted. You can always make shortcuts the player can hammer jump to if they want. Also, having to aim up or down in a fire fight is always fun. An example would be DM-Phobos. You can hammer jump to the armor from the hallway below, or you can also hammer jump up to the ledge from the area with pads/flak if the boots are gone. It's all part of flow and adds an element of surprise to the game. You just don't know where your opponent will pop up from. Also consider lift jumps. DM-Deck16][ is a good example of a useful lift jump for catching a player off guard. Deck16][ is also a great example of z-axis use. The multiple levels can make a level feel very large and complex.
Capture the Flag
Capture the Flag levels tend to be very sparing in their use of the z-axis. Most maps seem to either ignore it, or force the player to choose between a "high" route or a "low" route. There is generally very little traversal between routes, and that which does occur is normally in a downwards direction. CTF-Dreary is probably the map with the most z-axis use. Players can leave the base via a high route (using a BSP collision bug in the map) or through the middle platforms and then possibly drop down to the lower level. Travelling back up to the highest level is not possible. Other maps that make use of the z-axis are CTF-Gauntlet, and CTF-Orbital. It could possibly be said that CTF maps don't make enough use of the z-axis, but given the way the use of height can change a map flow this may be a good thing.
Assault
Use of the z-axis in Assault maps is a tricky feat to pull off. The Assault game type is purely objective based and it's hard enough to build a level that doesn't compromise game play in two dimensions let alone three. Some of the original Assault maps have z-axis routes, both intentional and unintentional. In AS-Overlord you can hammer jump over the bunkers to avoid the fox holes and mortar blasts. In AS-Frigate you can hammer jump up onto the deck of the ship and attack from there. In AS-Mazon it is possible to bypass the first objective and hammer jump right into the enemy base - one example of a z-axis route that was never intended by the map author. Some of the maps that come with the Eavy Assault Bonus Pack make good use of the z-axis, and it is these maps that I would use as reference rather than the Epic ones.
Bombing Run
Essentially a Bombing Run map involves a player running from their spawn position to a single point on the map to collect the ball, and then on to the other teams goal. A compass at the top of the screen indicates the direction from the player to the ball at all times. Since the compass doesn't indicate height, having the middle section of the bombing run map use many levels provides the ball carrier with more ability to confuse and evade the opposing team. Be wary of too much z-axis use on entry to the scoring areas within a Bombing Run map. Multiple entrances are fine but it's worth making sure that the scoring hoop can actually be defended. For example BR-Bifrost allows players to drop down into the base from above. Also, Bifrost has that platform that you shoot the ion painter to the ground. But, in order to score a goal you have to run a short distance - there is no way of scoring from above the base. Having said that, the Bombing Run maps shipped with UT2003 feel largely like flat surfaces with occasional changes in height and have little z-axis work. It's probably not a bad idea to always place the two scoring hoops at the same heigth within the map.
Types of Transportation
There are a few ways of travelling between the different levels of a map. Here's a list of the common ones.
- Lift
- Remember that people can "lift-jump" to gain extra height to access areas of the map that would otherwise be unreachable. If the lifts are too slow you will break up the action far too much - this is especially important in CTF maps. See Mover Topics.
- Jump Pad
- These bounce the player in a specfied direction. See also Lifts Vs Jumppads. These are made with:
- UT: Kicker and Pathnoding Kickers.
- UT2003: UTJumpPad
- Gravity Zone
- Players jump higer than normal. Dodges are also much faster. Don't change gravity in your map without a good setting or map "rationale". Otherwise it will look odd. See Gravity, Warp Tunnels.
- Nitrogen Zone
- Players can swim in these allowing them to move up and down. See NitrogenZone. Be aware that players in a Nitrogen zone look a little odd, and sometimes don't replicate very well.
- HammerJump
- This stings a lot but is an effective way of gaining a lot of height. The equivalent technique in UT2003 hurts much less and as such is more viable for map construction.
- Jump Boots
- Providing one or two pairs of jump boots on a level can give players the opportunity to escape pursuit by jumping up through the levels of your map when they cannot be followed.
- Warp portals and teleporters
- Personally I despise teleporters, and have real misgivings about warp portals. The mess with the map of the level I build in my head too much as they can be used to break the "structural integrity" of the map. See WarpZoneInfo, Teleporter for more information.
- Ramps and Stairs
- Having ramps or stairs that allow players to move between the layers of your level is a very common way of gaining footing on multiple levels. Generally ramps are preferred as although they are slightly more tricky to build (and error collision prone) they keep the number of polygons down. See Making Stairs and Making Ramps.
