A quick and dirty guide to perfect level changes

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Level changes are often over explained, and too complicated for their own good. There really is nothing to them and if you follow this tutorial step by step, you should have absolutely no trouble whatsoever.

What is a level change?

A level change is, simply put, a transition or displacement from one map (.bsp file) to another. And the reason you're reading this is because you're lost or trying to get a level change to work properly.

Why do I need level changes?

If you're thinking to yourself: "I can get by without them, and save myself a lot of hassle...", then think again!

Half-Life maps have limits. These limits should never be reached or pushed, you can read more about these in the general MAX_MAP limits part of Tommy14's errors page. If your levels are getting too big you should consider splitting them into 2 or more separate levels to avoid reaching these limits. This can be really useful for reducing r_speeds when working with two or more complex areas, or just to help you keep track of where you are in your map. Huge detailed maps are really difficult to work with in Hammer, as you probably already know.

How do I create level changes?

There are 3 types of level changes:

• Seamless: The simplest level change you can have - walk through a corridor, see some loading text, end up in another map, but your position in the corridor and the environment around you does not change. The place you end up in is a carbon copy of the place you have come from.
• Teleport: Same as above only the environment changes - i.e. go through a corridor in a lab and end up in your office/classroom searching for the 'check for problems' button in your life...It is a bit like teleporting, but you are doing it across maps.
• One-way: You can get there, but you can never return.

Seamless level changes

The only entities you'll need - since you just want a simple level change - will be trigger_changelevel (one in each map) and an info_landmark (also one in each map).

Start by making a suitable corridor:Now to add the info_landmark. Read very carefully is these details are critical:

The info_landmark sets up a constant point of reference in the origin and destination maps. It must appear in both maps otherwise the level change will not work correctly. The origin and destination info_landmark must both have the same Name (targetname) So basically, it's the same info_landmark in both maps.The Origin map trigger_changelevel:

Set these properties you need to change:

New map name: map2
Landmark Name: landmark1 (or whatever you called your two identical landmarks - one in each map)

The Destination map trigger_changelevel:

Set these properties you need to change:

New map name: map1
Landmark Name: landmark1 (or whatever you called your two identical landmarks - one in each map)Now, compile the maps through hammer or any other front-end compiler but remember not to run the game!, fire up hl with the console, and test the transition. If you did this correctly you should seamlessly jump from one map to the next no matter how you enter the trigger_changelevel.

One way level changes

You would think a one way level change would only require one trigger_changelevel?

Wrong.

You have to set the level change up exactly as you would for a normal change. The difference is that in the second map, reduce the size of the trigger_changelevel brush and move it somewhere that the player cannot get to it. That is what stops the player from going back. You can also check the Use Only Flag just to make sure those NoClipping players still can't get back.