DIY Chain rocket launcher

1. Get your favourite copy of the QC source. Or make a new one.
2. Open Weapons.qc, and scroll down to W_FireSpikes
3. Replace the lines

    dir = aim (self, 1000);
    launch_spike (self.origin + '0 0 16' + v_right*ox, dir);
   

   with:

    missile = spawn ();
    missile.owner = self;
    missile.movetype = MOVETYPE_FLYMISSILE;
    missile.solid = SOLID_BBOX;
   
   // set missile speed
    makevectors (self.v_angle);
    missile.velocity = aim(self, 1000);
    missile.velocity = missile.velocity * 1000;
    missile.angles = vectoangles(missile.velocity);
   
    missile.touch = T_MissileTouch;
   
   // set missile duration
    missile.nextthink = time + 5;
    missile.think = SUB_Remove;
    setmodel (missile, "progs/missile.mdl");
    setsize (missile, '0 0 0', '0 0 0');
    setorigin (missile, self.origin + v_forward*8 + '0 0 16');
   

   This is virtually the same as found in W_FireRocket, just without the bit that reduces your rocket ammo, plays the rocket launcher sound, and sets the punchangle. You'll want to add this at the top of W_FireSpikes:

    local entity missile;
   

4. You need to change

   setorigin (missile, self.origin + v_forward*8 + '0 0 16');
   

   to:

    setorigin (missile, self.origin + v_forward*8 + '0 0 16' + v_right*ox);
   

   to make sure it fires the rockets from alternating barrels of the nailgun.

5. You'll also want to change

    sound (self, CHAN_WEAPON, "weapons/rocket1i.wav", 1, ATTN_NORM);
   

   to:

    sound (self, CHAN_WEAPON, "weapons/sgun1.wav", 1, ATTN_NORM);
   

   to make sure it plays the rocket sound.

6. Now open items.qc, and scroll down to the weapons area. Find weapon_nailgun, and change the netname from 'nailgun' to 'Chain Rocket Launcher'.
7. Open client.qc, and scroll down to ClientObituary. Change:

       if (rnum == IT_NAILGUN)
       {
        deathstring = " was nailed by ";
        deathstring2 = "\n";
       }
   

   to:

       if (rnum == IT_NAILGUN)
       {
        deathstring = " was liquidized by ";
        deathstring2 = "'s chain rocket launcher\n";
       }
   

   Or some other comment. Deathstring is printed after the deceased's name, while deathstring2 is printed after the attacker's name:
   
   <deceased> <deathstring> <attacker> <deathstring2>
8. Save all the files and compile!
9. Further extenstion - adding some random inaccuracy. Go down to W_FireSpikes again, and change

    self.punchangle_x = -2;
   

   to:

    self.punchangle_x = 4 * crandom();
   

   This changes the punchangle (An offset to your view when you fire weapons, get hurt, etc) to a random number between -4 and 4 degrees pitch (crandom returns a number from -1 to 1, have a look at its definition at the top of weapons.qc)
   Unfortunately punchangle doesn't effect the direction your gun fires, so we'll have to do that ourselves. The vector missile.velocity is a direction for the rocket to head. We need to convert this into a set of angles, by using vectoangles. Below

    missile.velocity = aim(self, 1000);
   

   insert the lines:

    missile.velocity = vectoangles(missile.velocity);
   // Convert it to a set of angles (Stored as in a vector), format 'pitch yaw 0' as opposed to 'x y z'
    missile.velocity = missile.velocity + self.punchangle; // Add the punchangle to the direction the rocket's going.
    makevectors(missile.velocity); // Convert back to a set of vectors. The function sets global variables v_forward,
   v_right and v_up to point forward, right and up (Each has length 1).
    missile.velocity = v_forward;
   

   Hopefully the comments explain what's happening. Save and recompile to make this weapon a bit harder to use!

10. Another extension - punchangle_y. Just like punchangle_x, you can set the yaw. Simply insert the line:

     self.punchangle_y = 4 * crandom();
    

    underneath the punchangle_x line. You could also set punchangle_z (Roll, although few QC functions work with it).

11. Yet another extension. Like the last, this is simple. Change the

    4 * crandom()
    

    bits to

    2 * skill * crandom()
    

    for skill dependent inaccuracy! Skill 0 gives no inaccuracy, and skill 3 gives up to 6 degrees!
    Fiddle around with this bit as much as you want

12. No extensions this time. Now you've got to think up a few problems you're having, and ask me to write another of these handy file thingies for it!