Projectile speed dependent of direction vector length?

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Hi everyone, I have a question regarding my bullet speed. I've made a fire method which will trigger on mouseclick.

 public void Fire()
     {
         GameObject projec = Instantiate(proj, gunpoint.transform.position, gunpoint.transform.rotation) as GameObject; //Instaniate bullet
         Ray ray = playerCamera.ScreenPointToRay(Input.mousePosition); //get point by ray
         Vector2 dir = (ray.origin - transform.position).normalized; //Get vector direction between player and mousepoint clicked
         projec.GetComponent<Rigidbody2D>().velocity = projectile.speed * dir * Time.deltaTime; //Set projectile velocitymoving in direction vector with speed from other projectile script.
     }

However, when clicking close to the player, the direction vector becomes small --> slow speed of projectiles.

If clicking with a greater distance from the player, the distance vector becomes greater and the projectiles travels faster.

Have I interpreted this correctly? How would you guys handle firing a projectile from a gunpoint rotating around the player against a mouse point?

Thank you all Jonathan

Answer 1

Best Answer

Answer by Bunny83 · Feb 22, 2018 at 05:21 PM

Are you sure that's really the code that executes (forgot to save the recent changes)? The "normalized" at the end of this line:

 Vector2 dir = (ray.origin - transform.position).normalized;

will make the vector always have a length of "1.0". So what you describe would happen when you don't have that "normalized" at the end.

ps: You should remove that Time.deltaTime from your that line:

 projec.GetComponent<Rigidbody2D>().velocity = projectile.speed * dir * Time.deltaTime;

It makes no sense. The velocity is a property / state of the rigidbody. You only need to multiply be deltaTime when you have any additive process that is executed every frame. You set the speed once and the speed should be constant.

edit

I just saw where your problem might come from. ray.origin and transform.position are Vector3 values. That means the subtraction of the two will result in a Vector3. You then normalize the vector3 and finally assign it to a vector3 variable. So the conversion from Vector3 to Vector2 happens at the very end. If your vectors have any difference in the z direction that would be accounted for as well when normalizing. However when you do the V3 --> V2 conversion this amount is no longer present.

To fix this you can do this:

 Vector2 dir = ((Vector2)ray.origin - (Vector2)transform.position).normalized;

or this:

 Vector2 dir = (ray.origin - transform.position);
 dir.Normalize(); // or dir = dir.normalized;

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meat5000 ♦ · Feb 22, 2018 at 05:27 PM 0

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Just to simplify here, normalising a vector is the key. It prevents the effects like running faster at a 30 degree angle in Half-life.

Bunny83 meat5000 ♦ · Feb 22, 2018 at 05:43 PM 1

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Half-life never had this problem as far as i remember ^^. There is / was an issue when climbing ladders sideways. However normal movement is properly clamped to max speed. See the code. However many other games (especially indy games) have this problem. The actual strafe-jump / bunnyhop glitch happens server side.

meat5000 ♦ Bunny83 · Feb 22, 2018 at 05:57 PM 0

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Yeah I used to run around at 30 degrees for this reason. Undoubtedly was patched out at some point, but I'd long stopped playing by then, probably. I mentioned half-life because in that game it was most pronounced and noticeable. At glance at the code suggests that running normally was simply slower, but I only got 30 seconds. I'll look again later. Thanks for the snippet! :P

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johajo · Feb 22, 2018 at 05:57 PM 0

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Hey,

Thank you for the answer!

I have saved it - When debugging I get the direction vector to (0.0, 0.0), when clicking on the gunpoint (where the projectile is instansiated). If I click the edge of the screen, I get sometinhg like (0.6, 0.0)..

Debug added in code by:

     public void Fire()
     {
         GameObject projec = Instantiate(proj, gunpoint.transform.position, gunpoint.transform.rotation) as GameObject; //Instaniate bullet
         Ray ray = playerCamera.ScreenPointToRay(Input.mousePosition); //get point by ray
         Vector2 dir = (ray.origin - transform.position).normalized; //Get vector direction between player and mousepoint clicked
         Debug.Log(dir);
         projec.GetComponent<Rigidbody2D>().velocity = projectile.speed * dir; //Set projectile translation moving in direction vector with speed from other projectile script.
     }

Thank you for the Time.deltaTime remark, that makes sense.

Jonathan

johajo johajo · Feb 22, 2018 at 06:06 PM 0

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And to calrify, the problem persists

Bunny83 johajo · Feb 22, 2018 at 06:16 PM 0

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Yep, i've edited my answer ^^

johajo · Feb 22, 2018 at 07:02 PM 0

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Thank you so much! This worked excellent, using

  Vector2 dir = ((Vector2)ray.origin - (Vector2)transform.position).normalized;

Thank you! Jonathan

Projectile speed dependent of direction vector length?

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