Automatic cannon aiming

Question

Hello,

I am making cannon in 2D, which is aiming at the target automatically by calculating angle of shoot... I used range of projectile equation, it worked, but it was more like a howitzer, so I upgrade it to cannon style aiming by Quaternion.inverse. Problem appeared, when there was a difference between Y positions of cannon barrel and the target. Problem is because, when it is in normal form (without Quaternion changes) it needed only a little additional angle to shoot at upper or lower object. Now, when cannon aiming from 0 - 45 degrees (before changes it was 90-45) angle adjust only a little, like before my upgrades, so it need more additional angle. I actually tried lot of ways in hope to fix it, but no one seems to work. Guys, can you help me, please? :)

Before: alt text

After: alt text

     void Update()
         {
             x = (Target.transform.position.x - BarrelEnd.transform.position.x) * XMultiply;
             v = AmmoSpeed - Plusser;
             v2 = v * v;
             g = Mathf.Abs(Physics.gravity.y);
             y = (Target.transform.position.y - BarrelEnd.transform.position.y);
     
             Angle = Mathf.Atan((v2 + Mathf.Sqrt(v2*v2 - g*(g*x*x + 2*y*v2))) / (g*x));
     
             transform.rotation = Quaternion.Inverse(Quaternion.Euler(0,0, Mathf.Rad2Deg*Angle -               90));
         }

Answer 1

Answer by nebikhero · Apr 12, 2016 at 08:08 PM

@Vokyczech I created this piece of code 3 years ago, but i think it`s still working.

var Target: Transform; var grenadePrefab: Transform; var fireRate = 10; var attackRange = 20.0; var Damping = 6.0; private var Distance : float; private var nextFireTime = 0.0; function Start () { Target = PlayerTransform.playerTransform; } function Update(){ Distance = Vector3.Distance(Target.position, transform.position); if (Distance < attackRange) { Fire (); } } function BallisticVel(Target: Transform, angle: float): Vector3 { var dir = Target.position - transform.position; // get target direction var h = dir.y; // get height difference dir.y = 0; // retain only the horizontal direction var dist = dir.magnitude ; // get horizontal distance var a = angle * Mathf.Deg2Rad; // convert angle to radians dir.y = dist * Mathf.Tan(a); // set dir to the elevation angle dist += h / Mathf.Tan(a); // correct for small height differences // calculate the velocity magnitude var vel = Mathf.Sqrt(dist * Physics.gravity.magnitude / Mathf.Sin(2 * a)); return vel * dir.normalized; } function ElevationAngle(Target: Transform): float { // find the cannon->target vector: var dir = Target.position - transform.position; // create a horizontal version of it: var dirH = Vector3(dir.x, 0, dir.y); // measure the unsigned angle between them: var ang = Vector3.Angle(dir, dirH); // add the signal (negative is below the cannon): return ang; } function Fire () { if (Time.time > fireRate + nextFireTime){ nextFireTime = Time.time; FireOneShot(); } } function FireOneShot () { var ang = ElevationAngle(Target); var shootAng = ang +15; //shootAng = Mathf.Clamp(shootAng, 0, 360); transform.eulerAngles.z = -shootAng - 15; var grenade: Transform = Instantiate(grenadePrefab, transform.position, transform.rotation); var shoot = BallisticVel(Target, shootAng); shoot = Vector3(Random.Range((shoot.x - 20),(shoot.x + 5)), shoot.y, shoot.z); grenade.GetComponent.<Rigidbody>().velocity = shoot; //BallisticVel(Target, shootAng); // pass the angle and the target transform }

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Voky · Apr 16, 2016 at 07:11 PM 0

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I tried, but cannon didn´t move, even the variables are null... So, it isn´t working, but I don´t know, maybe it is caused by my JS skills... :D (btw thx for help)

using UnityEngine; using System.Collections;

 public class CannonUpgrade : $$anonymous$$onoBehaviour {
 
     public Transform Target;
     public Transform grenadePrefab;
     public float fireRate;
     public float attackRange = 20.0f; 
     public float Damping;
     private float Distance; 
     private float nextFireTime = 0.0f;
     public Vector3 shoot;
 
     private Vector3 dirH;
     
     // Update is called once per frame
     void Update () {
         Distance = Vector3.Distance(Target.position, transform.position);
         if (Distance < attackRange) 
         { 
             Fire (); 
         }
     }
     public Vector3 BallisticVel(Transform Target, float angle)
     {
         Vector3 dir = Target.position - transform.position;
         float h = dir.y;
         dir.y = 0;
         float dist = dir.magnitude;
         float a = angle * $$anonymous$$athf.Deg2Rad;
         dir.y = dist * $$anonymous$$athf.Tan (a);
         dist += h / $$anonymous$$athf.Tan (a);
         float vel = $$anonymous$$athf.Sqrt (dist * Physics.gravity.magnitude / $$anonymous$$athf.Sin (2 * a));
         return vel * dir.normalized;
     }
     public float ElevationAngle(Transform Target)
     {
         Vector3 dir = Target.position - transform.position;
         dirH.Set(dir.x, 0f, dir.y);
         float ang = Vector3.Angle (dir, dirH);
         return ang;
     }
     public void Fire()
     {
         if (Time.time > fireRate + nextFireTime)
         { 
             nextFireTime = Time.time; 
             FireOneShot(); 
         }
     }
     public void FireOneShot()
     {
         float ang = ElevationAngle (Target);
         float shootAng = ang + 15;
         shootAng = $$anonymous$$athf.Clamp (shootAng, 0, 360);
         transform.position = new Vector3(transform.position.x,transform.position.y,-shootAng - 15); 
 
         GameObject Grenade = Instantiate (grenadePrefab, transform.position, transform.rotation) as GameObject;
 
         Vector3 shoot1 = BallisticVel(Target, shootAng); 
         shoot.Set(Random.Range((shoot1.x - 20),(shoot1.x + 5)), shoot1.y, shoot1.z);
 
         Grenade.GetComponent<Rigidbody2D> ().velocity = shoot;
 
         BallisticVel (Target, shootAng);
     }
 }

nebikhero Voky · Apr 16, 2016 at 10:05 PM 1

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I tried JS version and its working in Unity 5.3.4. I'm not quite sure what`s wrong with C# version. $$anonymous$$y C# skill isn`t good enough. $$anonymous$$aybe you didn`t enter Target, grenadePrefab, fireRate manually in Editor?

I remember I had a similar problem, i manually added greater angle. float shootAng = ang + 15; // you can add any angle After ElevationAngle function calculates $$anonymous$$imum (like on your second picture) angle required to hit target

 function ElevationAngle(Target: Transform): float {
   // find the cannon->target vector:
   var dir = Target.position - transform.position;
   // create a horizontal version of it:
   var dirH = Vector3(dir.x, 0, dir.y);
   // measure the unsigned angle between them:
   var ang = Vector3.Angle(dir, dirH);
   // add the signal (negative is below the cannon):
   return ang;
 }

And after that. BallisticVel function calculates required velocity for the grenade with my desire angle (shootAng).

 function BallisticVel(Target: Transform, angle: float): Vector3 {
     var dir = Target.position - transform.position;  // get target direction
     var h = dir.y;  // get height difference
     dir.y = 0;  // retain only the horizontal direction
     var dist = dir.magnitude ;  // get horizontal distance
     var a = angle * $$anonymous$$athf.Deg2Rad;  // convert angle to radians
     dir.y = dist * $$anonymous$$athf.Tan(a);  // set dir to the elevation angle
     dist += h / $$anonymous$$athf.Tan(a);  // correct for small height differences
     // calculate the velocity magnitude
     var vel = $$anonymous$$athf.Sqrt(dist * Physics.gravity.magnitude / $$anonymous$$athf.Sin(2 * a));
     return vel * dir.normalized;
 }

$$anonymous$$aybe this small explanation with help you with your code.

Voky nebikhero · Apr 17, 2016 at 07:02 AM 0

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Thx, i will try that... :)

Voky Voky · Apr 17, 2016 at 08:58 AM 0

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 var Target: Transform;
     var grenadePrefab: Transform;
     var fireRate = 10;
     var attackRange = 20.0; 
     var Damping = 6.0; 
     private var Distance : float; 
     private var nextFireTime = 0.0; 
 
     function Start () 
     { 
            Target = PlayerTransform.playerTransform; 
        } 
        function Update()
        { 
            Distance = Vector3.Distance(Target.position, transform.position);
            if (Distance < attackRange) 
            { 
                Fire (); 
            } 
        } 
        function BallisticVel(Target: Transform, angle: float): Vector3 {
         var dir = Target.position - transform.position;  // get target direction
          var h = dir.y;  // get height difference
          dir.y = 0;  // retain only the horizontal direction
         var dist = dir.magnitude ;  // get horizontal distance
          var a = angle * $$anonymous$$athf.Deg2Rad;  // convert angle to radians
          dir.y = dist * $$anonymous$$athf.Tan(a);  // set dir to the elevation angle
          dist += h / $$anonymous$$athf.Tan(a);  // correct for small height differences
          // calculate the velocity magnitude
          var vel = $$anonymous$$athf.Sqrt(dist * Physics.gravity.magnitude / $$anonymous$$athf.Sin(2 * a));
          return vel * dir.normalized;
      }
        function ElevationAngle(Target: Transform): float {
            // find the cannon->target vector:
            var dir = Target.position - transform.position;
            // create a horizontal version of it:
            var dirH = Vector3(dir.x, 0, dir.y);
            // measure the unsigned angle between them:
           var ang = Vector3.Angle(dir, dirH);
            // add the signal (negative is below the cannon):
            return ang;
      } 
 
        function Fire () 
        { 
            if (Time.time > fireRate + nextFireTime)
            { 
                nextFireTime = Time.time; 
                FireOneShot(); 
            }
        } 
 
        function FireOneShot ()
        { 
            var ang = ElevationAngle(Target);
            var shootAng = ang +15; //
            shootAng = $$anonymous$$athf.Clamp(shootAng, 0, 360); 
            transform.eulerAngles.z = -shootAng - 15; 
            var grenade: Transform = Instantiate(grenadePrefab, transform.position, transform.rotation); 
            var shoot = BallisticVel(Target, shootAng); 
            shoot = Vector3(Random.Range((shoot.x - 20),(shoot.x + 5)), shoot.y, shoot.z); grenade.GetComponent.<Rigidbody2D>().velocity = shoot; //
            BallisticVel(Target, shootAng); // pass the angle and the target transform 
        }

+++

alt text

And still nothing :/

project.png (9.0 kB)

nebikhero Voky · Apr 17, 2016 at 12:42 PM 1

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I copy-paste your JS code and its working. Try to remove

     function Start () 
          { 
                 Target = PlayerTransform.playerTransform; 
             }

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Answer 2

Answer by Voky · Apr 17, 2016 at 06:53 PM

@nebikhero Thx, it´s finally working!!!

One last question: Have you any tip how to easily invert x position of aiming? Because the cannon shoot at the wrong side :D

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nebikhero · Apr 17, 2016 at 09:56 PM 1

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@Vokyczech Tune this line of code, because now it`s rotating cannon for shooting from right to left. $$anonymous$$ake it positive with desire angle. transform.eulerAngles.z = -shootAng - 15;

Voky nebikhero · Apr 18, 2016 at 05:13 AM 0

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Fine, it´s finally done! Thx for your patience and for piece of your own script...

Automatic cannon aiming

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