[SOLVED] How to stop PhysicsSprite from bouncing off Wall?

cocos2d-x JavaScript
1

I am creating a wall like this:

// Wall
    var bottomWall = new cp.SegmentShape(this.space.staticBody,
        cp.v(0, this.bottomWallHeight),
        cp.v(MAX_INT, this.bottomWallHeight),
        wallWidth);
    bottomWall.setElasticity(0);
    bottomWall.setFriction(0);

    this.space.addStaticShape(bottomWall);

And making a physicsSprite shape like this:

 // Create and add the physics shape
    var carShape = new cp.BoxShape(this.carBody, carSize.width * scaleCarSize, carSize.height * scaleCarSize);
    carShape.setElasticity(0);
    carShape.setFriction(0);
    this.space.addShape(carShape);

And then when a button is pressed I apply this force to the phyics shape:

// Apply down impulse on player
downImpulse: function () {
    this.carBody.applyImpulse(cp.v(0, -500), cp.v(0, 0));
},

Then when the carBody hits the wall segment, it bounces back and creates a constant force the other way. How can I make it so that the car just stops from moving any lower and stays against the bottomWall?

2

@efares

Try

bottomWall.setElasticity(-0.1);
3

I just tried it now, it didn’t change anything.

4

Then try change both to

bottomWall.setElasticity(-0.1);
bottomWall.setFriction(1.0);

carShape.setElasticity(-0.1);
carShape.setFriction(1.0);

Or you can stop the car in the collision begin function

collisionBegin : function ( arbiter, space )
arbiter.a
arbiter.b
5

Setting friction and elasticity to -0.1 and 1.0 did not work.

I got collision detection working between the car and the wall but how do I set the movement to 0 exactly?
What should arbiter.a and arbiter.b do?

6

@efares

Let’s say you have set the collision type as

wallShape.setCollisionType(wall);
carShape.setCollisionType(car);

arbiter.a and arbiter.b are the shape that collided and can be wall collide car or car collide wall, so a and b would switched.

So you can check the arbiter.a and arbiter.b collision type as

if(arbiter.a.collision_type == wall)
{
   //a is wall
   //b is car
}
else
{
   //b is wall
   //a is car
}

var bodyA = arbiter.a.getBody();
var bodyB = arbiter.b.getBody();

Then you can do anything to bodyA and bodyB to stop them like bodyA.setVel(cp.v(0, 0));
and may be can change their force and impulse, can’t find document how to do that, not sure available on JS version or not.

But if you want to remove the shape, you need do it in post step call back as

var self = this;
this.space.addPostStepCallback(function()
{
    self.space.removeShape(shape);
}
7

Thanks for your help. I tried that and then the car just went right through the wall. I’m not sure if I’m doing it wrong, I might not totally understand the logic of how physics works exactly since there isn’t much documentation about it in JS.

But…
I fixed my issue by comparing the height/position of the wall and height/position of the car then applied an equal and opposite force right before colliding.