CODEWITHSUNDEEP
objective-cioscocoa-touchphysicsbox2d
sumderungHAY
sumderungHAY

Reputation: 1337

Box2D dynamic body falling off screen

I basically have a rectangular object (like a spear) and I have a ground body. The problem is, when the spear hits the ground, it doesn't bounce back, it falls though and off the screen. Here my physics setup: (Ignore the ball reference, it suppose to be called spear (rectangular))

-(id) init {

    if( (self=[super init])) {

        CGSize winSize = [CCDirector sharedDirector].winSize;

        self.isAccelerometerEnabled = YES;
        self.isTouchEnabled = YES;

        // Create sprite and add it to the layer
        _ball = [CCSprite spriteWithFile:@"SPEAR.png" rect:CGRectMake(0, 0, 100, 10)];
        _ball.position = ccp(100, 100);
        [self addChild:_ball];

        // Create a world
        b2Vec2 gravity = b2Vec2(0.0f, -20.0f);
        bool doSleep = true;
        _world = new b2World(gravity, doSleep);

        // Create edges around the entire screen
        b2BodyDef groundBodyDef;
        groundBodyDef.position.Set(0,0);
        b2Body *groundBody = _world->CreateBody(&groundBodyDef);
        b2PolygonShape groundBox;
        b2FixtureDef boxShapeDef;
        boxShapeDef.shape = &groundBox;
        groundBox.SetAsEdge(b2Vec2(0,0), b2Vec2(winSize.width/PTM_RATIO, 0));
        groundBody->CreateFixture(&boxShapeDef);
        groundBox.SetAsEdge(b2Vec2(0,0), b2Vec2(0, winSize.height/PTM_RATIO));
        groundBody->CreateFixture(&boxShapeDef);
        groundBox.SetAsEdge(b2Vec2(0, winSize.height/PTM_RATIO), b2Vec2(winSize.width/PTM_RATIO, winSize.height/PTM_RATIO));
        groundBody->CreateFixture(&boxShapeDef);
        groundBox.SetAsEdge(b2Vec2(winSize.width/PTM_RATIO, winSize.height/PTM_RATIO), b2Vec2(winSize.width/PTM_RATIO, 0));
        groundBody->CreateFixture(&boxShapeDef);

        // Create ball body and shape
        b2BodyDef ballBodyDef;
        ballBodyDef.type = b2_dynamicBody;
        ballBodyDef.position.Set(100/PTM_RATIO, 100/PTM_RATIO);
        ballBodyDef.userData = _ball;
        b2Body *_body = _world->CreateBody(&ballBodyDef);


        b2PolygonShape spearShape;
        spearShape.SetAsBox(100/PTM_RATIO, 10/PTM_RATIO);
        b2FixtureDef ballShapeDef;
        ballShapeDef.shape = &spearShape;


        ballShapeDef.density = 1.0f;
        ballShapeDef.friction = 0.9f;
        ballShapeDef.restitution = 0.89f;

        b2Vec2 force;
        force.Set(_body->GetLinearVelocity().x+5.0f, _body->GetLinearVelocity().y+10.0f);
        _body->SetLinearVelocity(force);

        [self schedule:@selector(tick:)];
    }
    return self;
}

- (void)tick:(ccTime) dt {

    _world->Step(dt, 10, 10);
    for(b2Body *b = _world->GetBodyList(); b; b=b->GetNext()) {    
        if (b->GetUserData() != NULL) {
            CCSprite *ballData = (CCSprite *)b->GetUserData();
            ballData.position = ccp(b->GetPosition().x * PTM_RATIO,
                                    b->GetPosition().y * PTM_RATIO);
            ballData.rotation = -1 * CC_RADIANS_TO_DEGREES(b->GetAngle());
        }        
    }
}

Upvotes: 2

Views: 1067

Answers (4)

The Windwaker
The Windwaker

Reputation: 1054

I think only the fixtures are colliding in box2d. But your spear has no fixture. You only create the fixture def but not the fixture itself.

after setting restitution to you fixtureDef, add this line: 

_body->CreateFixture(&ballShapeDef);

Everything should then be fine !

A bit late I know..

Upvotes: 1

Andrew
Andrew

Reputation: 24846

I don't see anywhere in your code attaching the shapes to ball and to spear. If the body does not have a shape - it will not collide.

Upvotes: 1

iforce2d
iforce2d

Reputation: 8262

Edge fixtures do not collide with each other in Box2D. Make either the ground or the spear a polygon.

Upvotes: 0

Oscar Gomez
Oscar Gomez

Reputation: 18488

I haven't used cocos2d in a while, but I remember you needed to create an space an add the objects to it, so they were aware of each other.

Upvotes: 0

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