Rigidbody Velocity Not Added Properly

Question

I have a problem with adding velocity via JavaScript. This is that an object which is instantiated with the correct rotation and position is only given velocity as if the character were facing straight(level with ground).

I am doing this for a class in video game developement, and this assignment is already late, so it is 'imperative' for me to get it finished soon.

My Coding:

 function Shoot(){
     if(CanBeShot==true&&Reloading==false){
         //Insantiate a bullet at the tip of the gun
         var firedBullet:Rigidbody=Instantiate(Bullet,gunPos.position,gunPos.rotation);
         //Gun position(gunPos) is set to the tip of the gun, which has no collider
         firedBullet.velocity=transform.TransformDirection(Vector3(0,0,BulletSpeed));
         //Instantiate a flash effect
         Instantiate(MuzzleFlash,gunPos.position,gunPos.rotation);
         Physics.IgnoreCollision(firedBullet.collider,transform.root.collider);
         //Subtract from remaining ammo
         AmmoRemaining--;
         //Irrelevant to the problem:
         CanBeShot=false;
         yield WaitForSeconds(0.5);
         CockingSound.audio.Play();
         yield WaitForSeconds(0.5);
         CanBeShot=true;
     }
 }

Code in tutorial:

 var instantiatedProjectile:Rigidbody=Instantiate(projectile,transform.position,Vector3(0,-1,0),transform.rotation);
 instantiatedProjectile.velocity = transform.TransformDirection(Vector3(0,0,speed));
 Physics.IgnoreCollision(instantiatedProjectile.collider,transform.root.collider);

Answer 1

Answer by Kiwasi · Oct 22, 2014 at 02:36 AM

Why are you using two different transforms to set the rotation and velocity? Currently there is no relationship in your script between the bullet rotation and the bullet velocity.

You need to either set the velocity based on the firedBullet.transfrom.forward or gunPos.forward. Change line 6 to the following.

 firedBullet.velocity = firedBullet.transform.forward * BulletSpeed;

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roboaedin · Oct 22, 2014 at 05:53 AM 0

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First, I fixed it-- I was sure I had it on the camera, but the script was actually on the player. Second, is there any way to revoke a question asked? Third, I hadn't uploaded the whole script. That was just a snipped which I added comments to-- the part relevant to the former problem.

Answer 2

Answer by Owen-Reynolds · Oct 20, 2014 at 05:25 PM

Which direction is +Z on the gun? (the blue arrow, when the translate tool is set to local.) Is this script on the gun, or some other object?

o The line transform.TransformDirection(Vector3(0,0,BulletSpeed)); says to push the bullet along local +Z. Because standard Unity assumes that +Z is always forwards. Lots of people have models that aim +y or -z, ... . Several well-known ways to fix that.

This is so common, that transform.forward is a shortcut for tran.transDir(V3(0,0,1));. Both mean "my local forward." So most people would just write: velocity=transform.forward*bulletSpeed;.

o In transform.transDir... the transform refers to you -- the thing with the script on it. So if this script is on the player, it will fire the bullet whichever way the player is facing. It looks like the player "knows about" the gun through gunPos. So use gunPos.transDir... or just gunPos.forward.

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roboaedin · Oct 20, 2014 at 05:40 PM 0

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Wouldn't gunPos.forward move the gun tip forward A bit more info: Z is the correct axis. It is moving along that axis properly. The problem is that the bullet is ONLY being moved on that axis, with the exception of gravity. Despite the local Z axis of the bullet being pointed upward, it will only move on the local(to the character) Z axis. The actual rotation of the bullet is normal, right at the tip of the gun model I'm using. I can make a video as an example if necessary.

roboaedin · Oct 20, 2014 at 05:45 PM 0

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The gun and script are attached to the player's camera.

Owen-Reynolds · Oct 21, 2014 at 12:05 AM 0

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Wait. If the bullet has +Z facing up, and you say in your Q that the bullet has the correct rotation, that means the gun is facing up?

Is it a first person camera, so the gun always faces the way the camera does? So the camera is also facing up? Because the current code uses the camera's blue arrow as the firing direction.

One trick is just to simplfy. Fixed overhead camera. Try to fire a bullet from a "cannon" stuck to the ground. $$anonymous$$ake sure the cannon is spun and tilted, to be sure the direction is working. Can split screen Scene mode to look from any angle.

roboaedin · Oct 22, 2014 at 02:12 AM 0

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Yes, the gun is facing up. Yes, it's a first person camera. It shoots forward-- ONLY forward. If I aim upwards, it will still only go in that one direction. It is instantiated properly, with the right rotation, but the velocity does not seem to take that into account. This needs to be first-person.

I can get a video of the project uploaded if you need more information.

Rigidbody Velocity Not Added Properly

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