Rigid Body collision problem

Questions & Answers
1

Hi, I’ve run into a weird problem. I’ve asked something similar, but I feel I have now distilled the problem more clearly.

My goal is to have an object, object “A”, consisting of 2 objects, called for convenience Front and Back, which have the following demands:

-Front and Back are initially attached to each other and move together by player input

-Front and Back have different colliders and are supposed to receive different collider data. (So they need individual rigidbodies)

-Front and Back are both able to collide in every way with everything in the scene, including duplicates of object A. (So Front can’t be kinematic)

-Front has to be able to collide but must be unaffected by gravity. (So Joints didn’t work either)

The thing is, I’ve tried all sorts of setups, but I can’t get it to work properly. Its meant for a simple bumperkart game, where the front grill can at some point break off, but I’m absolutely dumbfounded by this particular problem. Any help would be appreciated.

2

“My main problem is, I need to differentiate between two colliders on one object”

fortunately it couldn’t be easier dude …

let’s look at the manual :slight_smile:

links to …

what do we have here …

et voila !

11923-collide.png
11923-collide.png981×342 88 KB 

function OnCollisionEnter(cc:Collision)
	{
	Debug.Log("I got hit ... ny name is ... " + gameObject.name);
	Debug.Log("but even better, here's the specific collider on this side ... " +
	    	cc.contacts[0].thisCollider.name );
	}

remember only ONE object has the RIGIDBODY – the HIGHEST LEVEL object.

put EACH OLLIDER on SEPARATE holder objects UNDER that object.

put my EXAMPLE script on the HIGHEST object (the one WITH the RIGIDBODY)

Hope it helps!!

Hey Broken - on these problems, it is REALLY MUCH EASIER if you just include an image and explain what you are trying to do. But I think I understand your problem.

I believe the likely solution to your problem is very simple:

“where the front grill can at some point break off…”

this is very common in games.

just have ONE COLLIDER for the overall car

the collider image is a CHILD of the overall car

have a collider on the bumper BUT TURN IT OFF

To make the bumper fall off:

(A) TURN ON the collider for the bumper

(B) … explained below …

(C) then make the bumper NOT a child of the car. in other words, on the bumper say transform.parent=null;

that’s it.

What is “point B” ? It should work fine with the above, but if you can be bothered, do this.

You can see that your car needs two different colliders. So, when you include the bumper, the car is a little longer right? When you have no bumper it is shorter. So simply, set up two different colliders for the car and swap between them. Or very simply - just change the length/centerpoint of the collider on there.

(Aside – as a matter of fact, on a simple game you can just even set the length of the collider automatically to match the bounds of the renderer.)

In general it’s important to understand this principle: when you have vehicles (or any thing in the game) that breaks apart or something “comes off”. You’re going to have really different objects before and after. Very commonly, say someone gets blown up and is dead – in fact you just swap to another totally different prefab or model after wards. (You make all the, say, arms, colors etc match and then swap from one to the other. the player thinks you have “altered the model” - say by the bumper falling off - but in fact you’ve trickily swapped to another totally different set of models. So this is precisely an example of that.

So it’s that simple I hope it helps!

By the way … “Its meant for a simple bumperkart game” … bumper kart games are extremely complicated! Vehicle games are much harder than shooters, etc.