PROJECT BREAKDOWN #1

AI FOR THE "BOTS"

The AI of the agents in this project, to which I will refer as "soldiers", responds to the standard design of enemy AI in modern shooter games, excluding some details such as tossing grenades, which could nevertheless be easily implemented with the current system.

This behavior is intended to mimic that of a human player.

The AI soldiers are programmed to:

• When no enemies are in sight, go to points of interest in the map, which are by default the spawn points throughout it, but can also be placed manually, like "capture points" usually are in FPS games

• After reaching their destination, move around, crouch, and stand up to avoid enemy fire

• Shoot enemies on sight, as well as approach them up to a set distance while firing to maximize accuracy

Additionally, I explored​ Unity's animation (including inverse kinematics) and particle systems, so there will be some references to those in the code.

The code for the AI is fairly simple and little is noteworthy. It is formed by a number of nested if-statements and sometimes for-loops, triggered by conditions related to seeing the enemy and distance to it or their goals. The movement is done with Unity's pathfinding system; and the sighting of enemies, with raycasting.

I'll share a few examples here, but you can download the whole Soldier.cs file below.

Here, for instance, is a loop that tries to find visible enemies while the soldier walks between points of interest before making contact:

//See enemies
            foreach (var item in FindObjectsOfType<Soldier>())
            {
                if (item.team != this.team)
                {
                    RaycastHit hit;
                    shotPoint.LookAt(item.targetTransform.position);
                    if (Physics.Raycast(shotPoint.position, shotPoint.forward, out hit))
                    {
                        if (hit.transform.root.GetComponent<Soldier>() && hit.transform.root.GetComponent<Soldier>().team != team && hit.transform.root.GetComponent<Soldier>() == item)
                        {
                            currenTarget = item.transform.root.transform;
                            targetPos = currenTarget.position;
                            lastPos = targetPos;

                            if (!GetComponent<AudioSource>().isPlaying)
                            {
                                GetComponent<AudioSource>().clip = sightClips[Random.Range(0, sightClips.Length)];
                                GetComponent<AudioSource>().Play();
                            }
                        }
                    }
                }
            }

It also plays a voice recording to indicate contact, following the style of recent FPS titles. While this loop being performed every frame might seem unoptimized, it did not reduce performance in my lowest-tier laptop, so I decided not to give it an every-second timer or anything of the sort.

Here is part of the function that enables shooting, which is done by physics as opposed to raycasting. Some variation of it is fairly common in most FPS titles, so I thought it might be interesting to show how I have done it:

if (ammoLeft > 0)
        {
            //Shoot if ammo available
            var _muzzleFlash = Instantiate(muzzleVFX, shotPoint.position, shotPoint.rotation);
            _muzzleFlash.GetComponent<AudioSource>().clip = weapons[selWeaponIndex].clip;
            _muzzleFlash.GetComponent<AudioSource>().Play();
           

            shotPoint.Rotate(Random.insideUnitSphere * spread);
            GameObject bullet = Instantiate(bulletPrefab, shotPoint.position, shotPoint.rotation);
            bullet.GetComponent<Rigidbody>().AddForce(shotPoint.forward * bulletSpeed);

            animator.SetTrigger("shoot");
            ammoLeft--;
            shootDelayLeft = maxShootDelay + Random.Range(-.01f, .01f);
        }

The laser projectile (here called "bullet" because I named it before designing the asset), on enemy impact, calls a function of the hit soldier that reduces its health. When that reaches zero, the soldier dies and respawns after a short while.