Note: if you've never used BSP before, I suggest that you review some of my General BSP tutorials to get a feel for using the editor. These tutorials for Quake-specific items will be geared to people who are already comfortable with BSP.

In earlier lessons we've used triggers without really explaining much about them. So I thought I'd take this lesson and delve deeper into the trigger entity and show you some different uses that can be applied to triggers. Download this map and load it into BSP and we'll get going.

Basically, a trigger is an invisible brush which interacts with other entities (doors, lifts, even monsters!) to make things happen in the Quake world. The list of things you can do with triggers would fill several lessons, so I'll just focus on a few things here. All triggers work pretty much the same way: when a player touches the trigger, the target of the trigger activates. Now one thing you might notice (you might have already noticed this). When you make triggers in your level, you don't have to assign a texture to them, since they're invisible. However, when QBSP runs, you might see an error message complaining that 'ENTITY is not a texture' or something similar. This is caused by having no texture assigned to a trigger brush. If you want you can assign a 'TRIGGER' texture to your trigger brush, but it's not required. As far as I know, Quake runs fine without it, despite the error. 'Nuff said, let's make some triggers...

In this lesson, we're going to make a secret room, hidden by a secret door (duh). Let's start off by making the room. Draw a 128x128 brush in the Top view, centered on (-640, -392). In a side view drag the ceiling of this brush to 128 and make sure the floor is at 0. Now make this brush into a room, with wall thickness of 8. (Remember you can edit the BSP.INI file to use the grid size as the default wall thickness).

While all the brushes of this new room are still selected, apply a texture of 'BRICKA2_2' to them. Switch to the Right View and select only the floor brush. We need to drag the right hand side of this brush over 8 units, to fill the space under the door we're going to make. This is just like we did when we made our other door in BSP General lesson 4. With the floor brush still selected, apply the 'FLOOR01_5' texture to it, so it will blend in with our other floor.

Now we're ready to make our door. Select the wall brush from our new room which is inside the wall brush of the room we originally made. When you get the proper brush selected, subtract it from the map, but don't delete it. This will make a hole in the wall, but leave the brush in place so we can make it into a door. Now since we want this to be a secret door, we don't want the player to know it's there, so we need to change the texture to match the surrounding wall. If you followed my suggestions in earlier lessons, the surrounding wall has a 'TECH03_1' texture which is stretched to 2.0 in the vertical direction (an SY value of 2.0). Go ahead and give your new door brush this same texture (or whatever texture you used on your wall). That way it will blend in and be invisible to the player.

With this door still selected, we might as well make our door entity, so switch over to the entity window and make this brush into a 'func_door_secret' entity with an angle of 180. Let's also assign a key/value pair of 'wait' '-1'. That way the door will stay open once it's triggered. Now if you want, you can switch over to Quake and try out your level. The secret door works, but you have to shoot it to open it. We'll fix that next by adding triggers, hence the name of this lesson :-)

Let's make it so the player has to shoot two buttons in order for the door to open. That way we can use the 'trigger_counter' entity. In order to do this, we'll need to make two buttons, so let's draw a 48x48 brush in the Right View, centered on (-120, 120). Assign this brush the 'SLIPTOPSD' texture. Now select the side of the brush which faces out into the room and assign it the '+2SHOOT' texture.

Switch to the Top View and draw your brush so that the top left corner sits on (-912, -96). Before we make this into a trigger, go ahead and copy the brush. Paste a copy and move it so that it is centered on (120, 120) in the Right View and the top left corner sits on (-912, 144) in the Top View. That should make our two buttons, so now let's make them into triggers. Select one of the brushes (it doesn't matter which one) and make it into a 'func_button' entity. Assign a key/value pair of 'health' '1' and another key/value pair of 'wait' '-1'. This tells Quake that the button must be shot in order to work and it will only be triggered once. When you get that button configured, select the other 'button' brush and do the same settings for it also.

Now, instead of linking these buttons to the door, we want to make an intermediate trigger to use instead. If we linked them to the door now, either one of them will open the door by itself. This isn't what we want. Since we want the player to have to shoot both of them, we need to make a 'trigger_counter'. Draw a new brush somewhere inside the room. It really doesn't matter where, since it's invisible, so just draw it somewhere out of the way, but make sure it's inside the room. If it's out in the void, we'll have a leak to fix!

Make this new brush into a 'trigger_counter' entity and assign a key/value of 'count' '2'. This tells Quake that there are 2 separate triggers which must be activated. The 2 is the default value and you really don't have to do this step, but I wanted you to see how it worked.

Okay, we've got our door, our two buttons and the counter; now let's link them together. To make this work properly, you must link all these entities together in the proper order. Any trigger that is improperly linked will not work. First, we need to connect our buttons to the counter, so select one of the brushes and then CTRL-CLICK on the 'trigger_counter' brush. This will link them together. Now select the other button and link it to the 'trigger_counter'. That has completed the first step in making our door work. We've linked the two buttons into one entity and made it so that they both must be activated for the trigger to fire. Now we need to link that to the door. To do this, select the 'trigger_counter' brush and then CTRL-CLICK on the secret door brush. Voila! That's all there is to it.

Now if you look in the top view, you should see purple lines leading from each button to the trigger counter and another purple line leading from the trigger counter to the door. Here's what mine looks like. Your map may vary slightly depending on where you drew your trigger counter brush.

The yellow brush in the center of the screen is my trigger counter. Notice how the purple lines lead from the two buttons to this brush and then a single line leads from there to the door.

Okay, now run your map in Quake and play around with your new buttons. Shoot one of them and you'll see a message appear telling you that there's one more. Shoot the second one and the message 'Sequence Complete' appears and the door opens. It doesn't matter which button you shoot first, the result is the same. You might be wondering how Quake knew to display these messages. That's because they are built into the trigger counter entity. You can override them by assigning a message key/value of your own, but it's not necessary.

Well, since this is a secret room, let's give the player credit for entering it. Let's also move the grenade launcher we drew earlier into this room so that it's hidden from the player at first. It's usually a good idea to hide the better weapons and artifacts from your player at the beginning of the game. This makes the game more challenging as they search for bigger and better weapons. Go ahead and select the grenade launcher entity and drag it into the secret room, making sure that it remains sitting on the floor.

Now, let's have Quake grant a 'secret' credit for the player entering the room. Switch to the Top View and draw a brush from (-704, -328) to (-576, -352). Switch to the side view and set the top of this brush at 128 and the bottom at 0. Now switch over to the entity window and make this brush into a 'trigger_secret' entity. Assign two key/value pairs: 'sounds' '1' (makes a quick beep) and 'message' 'You have discovered a secret area!' (shows a message to the player). Now when this trigger is activated, the player is granted credit for discovering a secret and a message is displayed. Re-run your level now and notice that the secret section of the status bar shows you have discovered 0 out of 1. Enter the secret room and the counter changes to 1 out of 1. Cool, huh?

Our secret room is cool, but it's pretty dark. Let's put a light in this room, but have it turned off until the player enters the room. To do this, we'll need to make a light attached to a trigger. Make a light entity in the normal way. I assigned a key/value of 'light' '150' to mine. Put this new light in the center of your secret room, centered vertically and horizontally. That way it provides light for the entire secret room. It's not too bright, but provides enough light for the player to see the grenade launcher sitting in the room. Once you've got the light created, click the 'START_OFF' flag in the entity window. This will make the light dark until it's triggered.

To trigger our light, let's make a trigger the same size and location as the one we just made (the secret trigger). Make this new trigger into a 'trigger_once' entity. With this new entity selected, link it to the light you just created. Now when the player enters the room, the light will come on at the same time the player sees the message. Try it out and see for yourself. Pretty slick!

Now let's put an exit trigger at the back of our secret room. If you moved the grenade launcher into this room earlier, make sure to move it near the door, so it will allow the player to grab the weapon without exiting the level. When you've got plenty of space near the back wall of this secret room, switch to the Top View and draw a brush from (-704, -432) to (-576, -456). In a side view, set the top of this brush at 128 and the bottom at 0. That makes the brush fill the entire back wall of the secret room.

Switch over to the entity window and make this new brush into a 'trigger_changelevel' entity. Since we don't have a map of our own to link to, let's go ahead and link this map to E1M1 (Slipgate Complex). Add the key/value pair 'map' 'e1m1' to this entity. You could leave this key/value pair off if you want and the current map will restart. If you want to link to some other map, enter its name instead of 'e1m1'. Just enter the filename of the map, with no extension.

You'll notice that there is a 'no_intermission' flag available on this entity. If you set this, there will be no intermission screen displayed when the player exits the map. I kind of prefer seeing an intermission screen myself, so let's leave this flag cleared. Now, we'll need to add an intermission spot. Quake uses the player start location for an intermission spot if you don't enter one of your own.

To add an intermission spot, switch to the Top view and draw a 32x32 brush centered on (-464, 176). Make this into an 'info_intermission' entity and add a key/value pair of 'mangle' '25 -135 0'. Notice you don't have to set an angle flag. You use mangle instead for this entity. If you understand roll, pitch and yaw, you'll have no problem figuring out the x,y,z numbers for the 'value' portion of this key/value pair, but it may take some trial and error to get it just right. When you've got it set, switch to a side view and drag this brush up until the bottom sits on 184 on the z-axis. Now, when the player exits the level, he'll see a view of the second room. Of course, you can have multiple intermission spots in your map; if you do, Quake will pick a random spot to display. Cool, heh? Here's our intermission screen:

Okay, now let's talk about some of the other triggers available in Quake. We won't actually draw anything in this part of the lesson, but there's a lot of important information. I don't profess to know everything about all the triggers, but I'll help you out with what I know. In addition to the triggers we've already covered in earlier lessons, Quake makes available the following triggers:

trigger_setskill

This trigger can be used to set the skill level of your map. Remember in BSP General lesson 3 I showed you how to make different monsters appear at different skill levels? Well, here's how you can let the player set the skill level for themselves. You can set up a teleport-type brush (like in the Quake start map), or you can attach this trigger to a switch or button; it's really up to you. In order to set the skill level, add a key/value pair to the trigger. The key is 'message' and the value is '0' (easy), '1' (medium), '2' (hard), and '3' (nightmare!). That's all there is to it! The level setting will take effect at the start of the next map, so it's usually handy to make a start map before getting into your main map.

trigger_relay

This trigger is fired by other triggers (it can't be touched by the player). It allows you to have multiple actions take place when the player trips a single trigger. In order to have it fire, make it the target of another trigger. For instance, when a player enters a room, you could have the lights go out, a crusher activate and a door open, all in sequence rather than at the same time. You can set a delay value for each trigger so that they will fire in sequence. Each trigger can have it's own message if you want and as far as I know, there's no limit to the number of relays you can string together. Just remember you don't want your player standing there watching stuff happen for 20 minutes :-)

trigger_monsterjump

This trigger can be used to ambush unsuspecting players. When triggered, the monster touching it will jump in the direction set by its angle flag. You can use this to have monsters jump off ledges to surprise players. If you've ever played the Critters map by Jim Lowell you know this can be used quite effectively to scare the hell out of a player! You can also set the height the monster jumps with a key/value pair.

trigger_hurt

This trigger can be used to damage a player. Used in conjunction with a trap, you can inflict the amount of damage set by the 'dmg' key/value pair. You can set doors and lifts to provide damage of their own, but this trigger can be used in instances where there is no damage flag available on an entity.

trigger_onlyregistered

This trigger will fire only if the player is playing the registered version of Quake. I'm not sure why this is here, because you can't play custom levels with the shareware version anyway, but here it is. If the player doesn't have the registered version, you can have a message displayed here, admonishing him to upgrade, naturally ;-)

Well, over the course of this lesson and the ones prior to it, we have covered every type of trigger entity available in Quake. By now you should have a strong grasp on how to use BSP and have enough tools available to make a complete map on your own. Since we're done with our tutorial map now, we won't be using it again. In future lessons I'll be demonstrating techniques in a more detailed fashion, but we won't actually be drawing a map per se.

One more thing before we leave this map. We haven't given it a name! Make sure no brushes are selected and switch over to the entity window. Since no brush is selected, you should see the Worldspawn entity displayed in the middle of the entity window. Add a key/value pair of 'message' 'Tutorial Map'. This will now display a title on the status bar of our map. While you're at it you can set the world type: 0 for medieval, 1 for metal, and 2 for base. This must be set if you want to use keys in your map (it controls whether you see a key or a keycard, for example). You can set which CD track to play here too if you want.

Well, that should give you an overview of triggers. Hope you found it useful.