I lied in my other article. Ok, it's not that big of a deal, but the most important aspect to a map, is not that you can have your fill of carnage, but rather that you can actually, within the game's limits, exit a level. What's the point of having all this beautiful architecture if you're trapped in there for years with no way to leave?
The way exits and other actions such as switches are dealt with in Doom, are called linedef actions. First things first, we're going to set up our first switch. Draw a 64x32 rectangle at the end of our slime pit. This will represent our switch. (A width of 64 is chosen because most switches are of that dimension)
In 3D mode, I'm going to lower the ceiling of that sector, and apply a switch texture. Click the ceiling, and drag it down to a height of 64. For the switch, I used SW1COMM, and LITE3 for the sides.
Now, to apply our exit effect. Much like with sector effects, linedef actions operate on a separate popup menu. Exit visual mode, and right click on the line with our switch. You should get a window like so:
The Settings have been explained in an earlier article, so we'll skip that. The section that we want to focus on is action. Click the little square beside the drop down arrow. Starting with the predefined actions, the possible actions are categorically sectioned off for ease. Expand any one of the subcategories with the [+] sign, and you should notice some letters.
W1/WR - Walk over once/repeatable. You must walk OVER the line, as touching it will not activate the action.
S1/SR - Switch once/repeatable. You press the switch using your use key to activate the button.
G1/GR - Gunfire once/repeatable. You shoot either a projectile or hitscan against the switch or an invisible line.
D1/DR - Door once/repeatable. Applying only to doors, this action is like an automatic switch that uses the door.
Creating doors, lifts, teleports and other contraptions will be covered later. For now, we're simply concerned with exiting the level. Expand the Exit section and have a look.
S1 Exit Level
G1 Exit Level
W1 Exit level
It's impossible to walk over a wall, so we can't use W1. G1's out of the question as well because we might accidentally hit the switch when fighting the baron, meaning that the only way to go is S1 Exit Level. Select that action and press OK.
You should notice that Doom Builder has changed the earlier window to [11 - S1 Exit Level]. Press OK again, and the line on the wall should have turned green. This indicates that an action has set to trigger for that line.
NOTE: Linedef actions are activated from the FRONT of the line, so the little line coming from the middle of the line must face the player for it to be activated.
And here's an image of our map in action:
You can download our finished sample wad: Mediafire (4 KB)
This article concludes the basics of creating a map, having covered the basics of using Doom Builder. The following articles will cover the creation of doors, tags, switches etc.