Q: How do you get one actor to follow another?
A: Here's a modified action from the A5 demo project.

entity* robot_boss;

action robot_master
{
   robot_boss = my;
   // put the rest of your code here
   // ........
}

action robot_slave
{
   var slave_target;
   var slave_speed;
   while (robot_boss == null) {wait (1);}
   while (1)
   {
      my.tilt = 0;
      slave_target.x = robot_boss.x - 50 * cos (robot_boss.pan); // stay 50 quants
      slave_target.y = robot_boss.y - 50 * sin (robot_boss.pan); // behind robot_boss
      slave_target.z = robot_boss.z;
      slave_speed.x = 7 * time;
      slave_speed.y = 0;
      vec_set (temp, my.x);
      temp.z -= 1000;
      trace_mode = ignore_me + ignore_sprites + ignore_models + use_box;
      slave_speed.z = -trace (my.x, temp);
      vec_set (temp.x, slave_target.x);
      vec_sub (temp.x, my.x);
      vec_to_angle (my.pan, temp);
      if (abs(slave_target.x - my.x) + abs(slave_target.y - my.y) > 30)
      {
           ent_move (slave_speed, nullvector);
           ent_cycle("walk", my.skill10); // play walk frames animation
           my.skill10 += 5 * time;
           my.skill10 %= 100;
      }
      wait (1);
   }
}

Q: I'm trying to write my own weapons. How can I attach particles to the trace instruction? I don't want the script written for me just an idea.
A: Trace sets "target" to the coordinates of the hit point. Place the line below after your trace instruction.

effect(your_particle_function, number_of_particles, target, initial_particle_speed);

Example: effect(hit_sparks, 10, target, vector(1, 1, 2));

Q: I have a model of a tree. I want to be able to walk right up to the trunk, but the bounding box won't allow me to do that because of the leaves.
A: Follow these simple steps:

- Add the tree model to your level and make it passable;

- Place a cylinder (a primitive) with 6-16 faces at the same position with the trunk and make it invisible.

Q: How can I close a gate (as a trap) behind the player if he's walking through a laser beam?
A: Place an entity close to the laser beam and attach it the action named "door_trigger". Create a wmb entity for the door and attach it the action named "door_trap".

entity* door_t;

action door_trigger
{
   my.invisible = on;
   my.passable = on;
   while (player == null) {wait (1);}
   while (door_t == null) {wait (1);}
   while (vec_dist(player.x, my.x) > 100) {wait (1);}
   while (door_t.z > 0) // final z = 0, play with this value
   {
      door_t.z -= 3 * time; // 3 = speed
      wait (1);
   }
   door_t.z = 0; // the door moves from 100 to 0 quants in this example
}

action door_trap
{
   door_t = my;
   my.z = 100; // initial z, play with this value
}

Q: I need some simple level changing code for a project that includes 9 levels. A simple box and a figure that shows the level number will do the job.
A: Click here to download the project.

Q: I'm making a game and I was wondering know can I insert a movie (avi) file. At a certain point the movie would be triggered.
A: Place any entity in your level and attach it the "movie_trigger" action; come close to it to start the movie.

action movie_trigger
{
    my.passable = on;
    while (player == null) {wait (1);}
    while (vec_dist(player.x, my.x) > 100) {wait (1);}
    media_play("my_movie.avi", null, 50);
}

Q: How would I go about reading the names of planets from a text file into an array, set random x, y and z coords for each planet, save these to a new file, and then load them as the player approaches?
A: Click here to download a project that reads five planet names from a text file named planets.txt, generates a random position for each planet and then writes the names and the coords in the processed.txt file. You will have to "ent_create" small, low poly entities at the positions given by processed.txt. Use those entities to check the distance between them and the player in a loop and create the corresponding planets when the player has come close enough to them.

Q: I tried the project from Aum37's faq (moveps2.zip) and I'd like to ask you to make a small change to it: when I turn and want to go in that direction I'd like to push "W" for forward, whatever direction that is.
A: Click here to download the modified project. Use "A" and "D" to rotate the player, "W" to move forward and "S" to move backwards.

Q: How can we make big levels with terrains but don't lose performance ?
A: Use several (smaller) terrain entities, and then use fog and decent camera.clip_far values. Take a look at the picture below: all the blue terrains will be rendered (this happens even if a single vertex is inside the camera.clip_far range), while the violet terrains won't be rendered. Don't forget to glue your terrains together nicely; I left that black space between them on purpose, because I wanted you to see them as separate pieces.