Not so much a scripting problem - Just need smart peoples' help.

Question

In designing a sort of flight combat game, I am needing to fire (Instantiate prefab, and move/target with separate script on prefab) a shot, which in the first frame, does a "Lookat Target" and moves forward after that..... I am getting the velocity.magnitude of the enemy ships rigidbody, and the distance between the player and the enemy, to calculate for how far ahead of the enemy ships' transform to set as the target, as in, "compensating for the fact that both the enemy and projectile are in motion".

What I have, is doing what I want - It's a formula that gives a smaller output ,targeting closer to the enemies' position, the closer the player is to the enemy when firing - and a larger output, targeting further ahead of the enemy position, the higher that ships' rigidbody.velocity.magnitude is.

Here is the code:

     using UnityEngine;
     using System.Collections;
     
     public class shotmover : MonoBehaviour {
         public float speed;
         public bool hasTarget;
         public Transform target;
         public Player player;
     
         public Vector3 targetahead;
     
     
         // Use this for initialization
         void Start () {
             player = GameObject.FindWithTag ("Player").GetComponent <Player> ();
             Destroyshot ();
 //Find out of the player has a target
             hasTarget = player.seesTarget;
 //If they do,
             if (hasTarget) {
     //Store that object
                 target = player.locktarget;
 /*add to targetahead, forward from the enemy, higher the further you are from the target, divided by 100 because i am just dumb, and higher based on the velocity of the enemy ship.*/
                 targetahead += target.position + target.forward * (((Vector3.Distance(transform.position, target.position)) / 100) * (1+player.locktarget.gameObject.GetComponent<Rigidbody> ().velocity.magnitude));
                 transform.LookAt (targetahead);
                 Debug.Log ("target velocity:" + player.locktarget.gameObject.GetComponent<Rigidbody> ().velocity.magnitude.ToString ());
     
     
             }
         }
     
         void Update () {
             gameObject.transform.Translate (Vector3.forward * speed);
             if (hasTarget) {
                 Debug.DrawLine (gameObject.transform.position, targetahead);
                 Debug.DrawLine (target.transform.position, targetahead);
             }
     
         }
     
     
         void Destroyshot(){
             Destroy (gameObject, 2f);
         }
     }

In my little formula there, I am diving by 100 because the player will only target things about 100 units away. And I knew that the velocity output would average out around 1.So I was just kind of spitballing from debug logs!

Here is an image of how that is working:

http://i.imgur.com/khWH49D.png

The help that I need is this: What would be the most accurate way, or even a more accurate way, of calculating targetahead? I drew a little triangle at the bottom of that image, to represent the situation, and the Pythagorean theorem popped into my head. But I can't quite put anything together that cohesively grabs the right values for something like that. Any ideas, Pythagorean or otherwise?

Answer 1

Answer by elenzil · Jan 13, 2017 at 12:40 AM

here's the math,

here's an implementation of the math,

here's a demo of the implementation.

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Thomas-Hawk · Jan 13, 2017 at 03:54 AM 0

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THANK YOU SO MUCH. Going to play with it now.

Thomas-Hawk · Jan 13, 2017 at 05:36 AM 0

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How might I ring this effect up in a 3d worldspace?

Or does it not matter, since we're only dealing with one plane of calculations either way?

Thomas-Hawk · Jan 13, 2017 at 03:41 PM 0

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I understand the last part would be written roughly like this,

Projectile velocity = [Target position - Projectile position + Target velocity * time of collision] / collision time

Or, shot.rb.velocity = [ target.position - shot.position + target.rb.velocity * time of collision....

The time part, I do not get. I understand the importance of the variable but Please tell me, How would "time of collision" be implemented in the actual code ?

Thomas-Hawk Thomas-Hawk · Jan 13, 2017 at 04:07 PM 0

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Furthermore, I see what you seem to be solving for is ultimately what I need to set the speed of the projectile to? I need a position vector to plug in, my projectile, and every projectile I fire, will have the same speed / velocity, every time.

elenzil Thomas-Hawk · Jan 13, 2017 at 06:16 PM 0

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speed and velocity are not the same thing.

velocity is a vector, which has both length and direction. speed is just a scalar, ie a single value.

the code i provided takes these inputs:

the position of the target
the velocity (vector) of the target
the position of the projectile at the beginning (or you could think of this as the position of the cannon)
the speed of the projectile

and it outputs: * whether or not it's possible for the projectile to hit the target

if it is possible, the velocity (vector) the projectile should use in order to hit the target. the length of this vector will be equal to the projectile's speed.

elenzil Thomas-Hawk · Jan 13, 2017 at 06:19 PM 0

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the routine i wrote takes care of the time variable internally.

re 3d vs 2d, the code is 3d. if your situation is 2d, that's fine too, the 3d code will work.

Thomas-Hawk · Jan 13, 2017 at 03:58 PM 0

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also, your demo is missing a lot of things, and is not playable.

elenzil Thomas-Hawk · Jan 13, 2017 at 06:12 PM 0

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hm, that doesn't sound right. can you be specific ?

elenzil Thomas-Hawk · Jan 13, 2017 at 06:30 PM 0

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exported to HTML: https://elenzil.github.io/unityUtils

Thomas-Hawk elenzil · Jan 14, 2017 at 08:46 AM 0

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that is so friggin awesome sir. i am going to try very hard to implement this into my game, even though i still only half understand the script / math.

if i sent you a project with the stuff im trying to apply it to, could you help me?

Thomas-Hawk · Jan 14, 2017 at 07:18 AM 0

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Thank you a bunch. I can't seem to figure out how to turn the calculations considering the canvas scale etc into the ones I need (distance during start frame etc)....and the target as gameobjects targetable by my player etc....Help me out?

Answer 2

here is what I am ending up using

  showme2 = (Vector3.Distance (transform.position, target.position));
                 //targetahead += target.position + target.forward * (((Vector3.Distance(transform.position, target.position)) / 100) * (player.locktarget.gameObject.GetComponent<Rigidbody> ().velocity.magnitude));
                 targetahead += target.position +  (target.GetComponent<Rigidbody>().velocity) + player.locktarget.gameObject.GetComponent<Rigidbody> ().velocity/showme2*(Mathf.Sqrt((Mathf.Sqrt(showme2)/speed) * (Mathf.Pow(Mathf.Sqrt(player.locktarget.gameObject.GetComponent<Rigidbody> ().velocity.magnitude), rb.velocity.magnitude)+Mathf.Pow(showme2, Mathf.Sqrt(showme))-Mathf.Sqrt(showme)+Mathf.Sqrt(player.locktarget.GetComponent<Rigidbody>().velocity.magnitude))));
                 //targetahead += target.position - player.locktarget.gameObject.GetComponent<Rigidbody> ().velocity * (Mathf.Sqrt((Mathf.Sqrt(showme2)) * (Mathf.Pow(player.locktarget.gameObject.GetComponent<Rigidbody> ().velocity.magnitude, rb.velocity.magnitude)+Mathf.Pow(showme2, Mathf.Sqrt(showme))+Mathf.Sqrt(showme)+Mathf.Sqrt(player.locktarget.GetComponent<Rigidbody>().velocity.sqrMagnitude))));
                 transform.LookAt (targetahead);
                 Debug.Log ("Target velocity:" + player.locktarget.gameObject.GetComponent<Rigidbody> ().velocity.magnitude.ToString ());
                 showme = (Vector3.Distance(targetahead, target.position));

Here is a playable demo of that in action. http://tomahawkhomepage.x10host.com/newdemo/

WASD R SPACE

Not so much a scripting problem - Just need smart peoples' help.

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