Is it Possible to Stop a Child Object Moving and Rotating like the Parent Object Does?

Hi

This is my problem. I have an asteroid in my top down shooter which rotates randomly and moves randomly on the X and Z axis. Everything must stay at 0 on the Y axis. When my asteroid is destroyed, it spawns 4 more where it is destroyed. To achieve this I had to attach 4 empty game objects to spawn my other asteroids which I placed above, below, left and right of it (looking down onto the asteroid from above that is) (See screenshot).

At the moment when the asteroid rotates, the spawn points follow its rotation so when they do spawn they can be spawning off of 0 on the Y axis lets say something like -2 to 2.

How can I make the child objects (spawn points) follow the asteroids position X and Z position without moving on the Y.

I don't think I'm explaining it very well so bear with me. I have a screen shot to sort of explain the set up. I may be approaching this all wrong.

Thanks for reading and I hope someone knows what I'm getting at. Cheers


EDIT: The Spawn prefab with the game object placed at position 0, 0, 0

 

Easiest approach is to reset the y position each frame (e.g. in Update() ).

 

just make another prefab with 4 small ones and spawn it on big asteroid position,
dont need to parent anything hierarchy is not for that.

 

At the moment I have my Large Asteroid prefabbed with the 4 spawn positions attached to it and a small Asteroid prefab. Do you mean if I was to create an empty game object at 0, 0, 0 and have the 4 small asteroids placed on that, prefab it as 'Spawn' and then instantiate Spawn prefab when Large Asteroid gets destroyed? @pointcache

 

Or even better, one small stone is a prefab, and big one instantiates it 4 times offsetting direction vector to random value,
then destroying himself.

 

Also small stone prefab can use random stone models when instantiating.

 

Ahhhh, I like that idea.

This is my instantiation code on the large Asteroid that is run when it detects a collision and I already have a small asteroid prefab. So to achieve that I would only need to change a few lines? Would you mind showing me an example of the sort of code you would us for that please. @pointcache

Code (CSharp):

1.  
2.         Destroy (other.gameObject);
3.         Destroy (gameObject);
4.  
5.         Instantiate(mAsteroid1, spawnUpper.position, transform.rotation);
6.         Instantiate(mAsteroid1, spawnLower.position, transform.rotation);
7.         Instantiate(mAsteroid1, spawnLeft.position, transform.rotation);
8.         Instantiate(mAsteroid1, spawnRight.position, transform.rotation);
9.  

 

Code (CSharp):

1.    
2.     void RektAsteroid(int HowManySmallToProduce, bool isRandom)
3.     {
4.         if (isRandom)
5.         {
6.             for (int i = 0; i < HowManySmallToProduce; i++)
7.             {
8.                 Vector3 dir = Random.insideUnitSphere;
9.                 dir.y = 0;
10.                 GameObject currentAsteroid = Instantiate(SmallAsteroid, BigAsteroid.transfor.postion, Quaternion.identity);
11.                 currentAsteroid.transform.rotation = Quaternion.Euler(dir);
12.                 //apply impulse here
13.  
14.             }
15.         }
16.  
17.         else
18.         {
19.             //use your predefined values , say:
20.             Vector3 up = Vector3.up; //and then kill the y
21.             up.y = 0;
22.         }
23.     }

i would do something like this

i probably made a lot of mistakes there esp with euler/quternion but im showin the idea.
I like this approach, when you are able to customize the outcome of whats going on, and substitute elements. Once written this "explosion spawner" method you can reuse it feeding
him say scrap metal from ship explosions, etc etc.

 

Crikey! I can just about keep up with that but I can see how efficient it is. I don't know if i'll be able to make that work but I will give it a go. Might take a while. Thanks for making that up for us.

However, I did try the other idea about making a spawn prefab with asteroids in it (all at 0 on the Y). Took a screen shot of it (In the main description now) and the code that I am instantiating it with.

Code (CSharp):

1. Instantiate(mAsteroid1, other.transform.position, transform.rotation);

(mAsteroid1 - holds my Spawn prefab)

now to me that should work perfectly, but I get the same result. They are still being instated all over the Y axis and I don’t see how they can be. @pointcache

 

instead of directly using other object transform, put it into variable first, kill the y axis in it, and then use it for instantiation.
by killing i mean = 0

 

I would kill the Y by doing something like this right?

Code (CSharp):

1. currentPosition = transform.position;
2. currentPosition = transform.position.y = 0.0f;

 

Code (CSharp):

1. Vector3 store_position = transform.position;
2. store_position.y = 0;
3. instantiate(bla-bla, store_position)
4.  

 

Couldn't you just make your asteroid object the child of an empty object... have the asteroid do its tumbling and such but the actual movement across the screen is done on the parent.... have your spawners children of that parent as well.

 

Big Bang Theory moment! You must be looking at us like Penny does here. lol

Cheers thats a simple way of doing it.

 

heh I wasn't looking at you guys like that... just figured I'd throw up a solution I'd use since I didn't see it mentioned.

 

Well, I've made a parent object for the asteroid and the spawn points. I've ended up having to put all the scripts onto the main parenting object which works so far. The only snag is my RandomRotator script to make the asteroid tumble I have to put it on the asteroid child object. I'm starting to get the impression that scripts on child objects don't tend to work at all? @novashot

 

Tell a lie. Rigidbody would help.

Now thats rotating, the asteroid doesn't want to move with the parenting game object. The spawn points are running off and leaving the tumbling asteroid behind. One thing after another. No idea. @novashot

No it makes no difference whether the asteroid is rotating or not.

Answer = Cant have two rigidbodies spread over parenting and child objects.

 

This way will work, I can't have two rigid bodies spread over parenting and chid objects. Is there a clever solution to this @pointcache. Sorry I keep discovering problems.

 

What is the intended behavior... do your shots alter its trajectory? alter rotation?

it's true you can have multiple rigid bodies put down, but they will be combined in the parent/child relationship... if the shots only alter the trajectory, have the rigid on the parent and just script a simple rotational effect for the asteroid object... if the shots are supposed to affect trajectory and rotation of the asteroid... it will get a bit trickier.

 

The shots from the player are designed just to destroy. My RandomRotation script was on the main parenting object for spawn points and asteroid but that caused the spawn points to rotate with the asteroid. So I tried to put the RandomMover script on the main parenting object whilst the rotator script was on the child asteroid object. Both scripts use velocity and require the ridbody. Which doesn't work very well as either the astoroid will rotate and the spawn points will move off without the asteroid or the spawn points will move off and asteroid won't follow properly and just jerk around in the same spot. They don't combine very well. @novashot