Is there a way to make certain triggers occur if a player exist? Say, I wanted to make like a campaign map. And Units would be created for me when I'm playing. But what about Player 2? I could say, create units for Player 2 also, but if I was playing alone, that human controlled character would be generated, regardless if there even was a Player 2 playing.

Any ideas?

Triggers dont execute under non existent players. Place the trigger creating the characher for Player 2 under himself.

Put all humans in the same force and make a trigger for that force that creates the units for current player.
This won't work if players have different units. In that case set make individual triggers. Like this:
Player 1
Always
create marine for current player

Player 2
Always
create hydralisk for current player
... etc.

Post has been edited 1 time(s), last time on May 18 2008, 8:23 am by NudeRaider. Reason: improved alternative

If you want to check if a player is present, you can run a trigger under every player, such as set a switch for each player, and then you can check if the trigger has run(the switch has been set) to tell whether the player is there or not.

But if you have a map having all 8 human players you dont know where to check

What do you mean exactly? If you mean the existence of a player as a condition, yes that's possible by doing what people above have described. Do you mean just have triggers fire regardless of whether a player is there or not, or... something else?

I won't answer for exo_kopaka but I think he means existence of a player as a condition But it also is possible to make triggers fire regardless of whether a player is there or not, do you know how?)