Autoaim

From Doom Wiki

[edit] Vertical autoaim

[edit] Horizontal autoaim

The player's projectile weapons have a limited ability to adjust their direction if the nearest target is not exactly straight ahead. From P_SpawnPlayerMissile in p_mobj.c:

   // see which target is to be aimed at
   an = source->angle;
   slope = P_AimLineAttack (source, an, 16*64*FRACUNIT);
   
   if (!linetarget)
   {
       an += 1<<26;
       slope = P_AimLineAttack (source, an, 16*64*FRACUNIT);
   
       if (!linetarget)
       {
           an -= 2<<26;
           slope = P_AimLineAttack (source, an, 16*64*FRACUNIT);
       }
   
       if (!linetarget)
       {
           an = source->angle;
           slope = 0;
       }
   }

An angle in the Doom engine is 32 bits, so that 1<<26 = 360° × (2²⁶ ÷ 2³²) ≈ 5.6°.