Hey, a lot of people kept asking for a camera collision, so here is one
Code:
  
var Temp_distance = 0;
var Distance_traced = 0;
Function Camera_Collision()//include this in your camera code
{
	my = player;
	trace_mode = ignore_me + ignore_passable + use_box + ignore_models;//you can remove ignore_models if your level is made with a lot of models.
	vec_set(temp_distance.x, camera.x);
	Distance_traced = trace(player.x, Temp_distance.x)
	if((Distance_traced != 0)) 
	{
		Distance_traced -= .05;
		camera.x = player.x - distance_traced * cos(camera.pan)-1;
		camera.y = player.y - distance_traced * sin(camera.pan)-1;
	}
}

It's similar to one of the AUM's except it won't dig into walls and some modifications.

I do not solve problems.... I prevent them.