ddmyx/objects/oCamera/Step_0.gml

if instance_exists(follow)
{
    x_to = follow.x;
    y_to = follow.y;
}

x += (x_to - x) * smooth;
y += (y_to - y) * smooth;

x = clamp(x, cam_width/2, room_width - cam_width/2);
y = clamp(y, cam_height/2, room_height - cam_height/2);

var _cam_x = x - cam_width/2;
var _cam_y = y - cam_height/2;
camera_set_view_pos(view_camera[0], _cam_x, _cam_y);