Respawning Objects in GTA 2 Mission Scripts

Elypter first used this technique on a FOOTBALL in one of this Blast City levels. Now I use it to respawn knockable barricades to stop shortcuts in my Macau, Monaco & Suzuka race map.

The example starts a thread where the objects respawn. This leaves your main loop free to create missions and game modes.

How it Works

Every 30 seconds, we destroy the object and then recreate it. We check whether any players can see the area before doing this. We don’t check the specific object, because that adds a lot of code.

Objects & Commands
`OBJ_DATA`	Creates the type of object you want initially.
`COUNTER`	Lets you respawn an object at regular intervals. Also avoids respawning too many objects at the same time.
`THREAD_TRIGGER`	Starts the respawn code and lets it run separately from the main mission loop.
`THREAD_WAIT_FOR_CHAR_IN_AREA_ANY_MEANS`	This is the type of trigger, chosen so it always runs. Just make sure it covers the Player 1 start point!
`IS_POINT_ONSCREEN`	Checks whether any player can see a particular location, with a single line of code!
`EXPLODE_SMALL`	Kills the object, so the game can recycle it.
`DELETE_ITEM`	This removes the object immediately. Only works after you have exploded the object, though!
`CREATE_OBJ`	Makes a new object to replace the old one.

Add to Existing Levels

You can simply Copy and Paste these examples before LEVELSTART, with some changes:

Adjust the object types so you get the things you want.
Change the co-ordinates so they appear in the right place.
Change the object names so they make sense in your level.
Be especially careful with COUNTER names to avoid conflicts with other loops.

Timing Control

Sadly you cannot check if most object types have been knocked over. The best workaround is to respawn it every 30 seconds. If you make sure no players can see the area this creates a realistic effect, as if city workers are cleaning up and repairing things after you leave the area for a while.

This requires an invisible timer which we can create using the COUNTER object. We’ll increase the count every frame and reset it every 30 seconds.

For realism we’ll add a check to make sure the player cannot see the area. If you only have one object in each area, you can check whether they can see that specific object directly. Light objects might be pushed far outside of the area but if you have a lot of objects, checking each one adds a lot of code.

Example of the Objects

Just like a normal scenery object, I create the red and white police roadblock barrier:

OBJ_DATA turn1_1 = (036.2,075.5,255.0) 090 ROADBLOCK

This will appear straight away, at the start of the game. But we also need timing and a COUNTER for the loop:

// Respawning Objects
COUNTER respawn_timer
ONSCREEN_COUNTER respawn_timer_onscreen

// Monaco Barriers
OBJ_DATA turn1_1 = (036.2,075.5,255.0) 090 ROADBLOCK


// Loop
COUNTER stage = 1

Evil Tricks

The DELETE_ITEM command should remove the object. But that doesn’t work! You’ll just get more and more of them stacked up on that same spot, until the game crashes.

Elypter discovered that if you EXPLODE_SMALL the object, then DELETE_ITEM it, that will remove it. Hooray!

However, seeing the object explode is a bit weird. This is another reason to only respawn an object when nobody can see it.

Complete Example with Working Code

Before the LEVELSTART but after all your other objects, add the respawn code:

// Upward Timer
// http://gtamp.com/forum/posting.php?f=4&t=147#p5857
FORWARD upward_timer:
COUNTER timer = 1 // count frames from 1-30 every second
TIMER_DATA time_taken // display the time taken
THREAD_TRIGGER upward_trigger = THREAD_WAIT_FOR_CHAR_IN_AREA_ANY_MEANS(
                                p1, 175.0,063.2,1.0, 4.0,4.0, upward_timer:)
upward_timer:
 // Setup
 DELAY_HERE (330) // wait for Time Limit to go away
 // ADD_ONSCREEN_COUNTER (respawn_timer_onscreen, respawn_timer) // test
 DISPLAY_TIMER (time_taken, 11) // 330 frames = 11 seconds

 // Respawning Objects
 // Note: Barricades get knocked around, so respawn them.
 ++respawn_timer // count 1 frame

 // Respawning Objects for Monaco
  IF (respawn_timer = 300) // after 10 seconds
  // Note: respawn_timer continues for Suzuka objects

   // Turn 1:
   IF (NOT (IS_POINT_ONSCREEN(036.2,075.5,1.0)) )
    EXPLODE_SMALL (turn1_1)
    DELETE_ITEM (turn1_1)
    turn1_1 = CREATE_OBJ (036.2,075.5,255.0) 090 ROADBLOCK END
   ENDIF
 ENDWHILE
RETURN

This carries out all the respawn requirements.

Tested in single player and multiplayer many times. It works perfectly if you set it up correctly.