Collision detection Fail in Box2d

Question

I want to detect collision between bodies, one body has circle shape and 30+ have convex body. Maybe problem is because of detecting collision between circle and convex? Please help, can't find the answer for 2 days... I have 3 classes: Player, ConctactListener and level1(where I create polygons).

In Player I set the type kGameObjectPlayer:

    - (id) init {
        if ((self = [super init])) {
            type = kGameObjectPlayer;
        }
        return self;
    }
-(void) createBox2dObject:(b2World*)world {


    b2BodyDef playerBodyDef;
    playerBodyDef.type = b2_dynamicBody;

    playerBodyDef.position.Set(self.position.x/PTM_RATIO, self.position.y/PTM_RATIO);
    playerBodyDef.userData = self;
    playerBodyDef.fixedRotation = true;

    body = world->CreateBody(&playerBodyDef);

    b2CircleShape circleShape;
    circleShape.m_radius = 0.7;
    b2FixtureDef fixtureDef;
    fixtureDef.shape = &circleShape;
    fixtureDef.density = 1.0f;
    fixtureDef.friction = 1.0f;
    fixtureDef.restitution =  0.0f;
    body->CreateFixture(&fixtureDef);
}

In ContactListener:

    void ContactListener::BeginContact(b2Contact *contact) {
    GameObject *o1 = (GameObject*)contact->GetFixtureA()->GetBody()->GetUserData();
    GameObject *o2 = (GameObject*)contact->GetFixtureB()->GetBody()->GetUserData();

    if (IS_PLATFORM(o1, o2) && IS_PLAYER(o1, o2)) {
        CCLOG(@"-----> Player made contact with platform!");
    }
}

void ContactListener::EndContact(b2Contact *contact) {
    GameObject *o1 = (GameObject*)contact->GetFixtureA()->GetBody()->GetUserData();
    GameObject *o2 = (GameObject*)contact->GetFixtureB()->GetBody()->GetUserData();

    if (IS_PLATFORM(o1, o2) && IS_PLAYER(o1, o2)) {
        CCLOG(@"-----> Player lost contact with platform!");
    }
}

And in level1 I create static polygones that should be a ground with which player should contact.

    - (void) drawStaticPolygons
    {
        GameObject *ground = [[GameObject alloc] init];
        [ground setType:kGameObjectGround];

        //1st polygon
        b2Vec2 vertices1[4];
        vertices1[0].Set(0, 1);
        vertices1[1].Set(0, 0);
        vertices1[2].Set(16, 0);
        vertices1[3].Set(16, 1);

        b2BodyDef myBodyDef1;
        myBodyDef1.type = b2_staticBody;
        myBodyDef1.userData = ground;

        b2PolygonShape polygonShape1;
        polygonShape1.Set(vertices1, 4); 

        b2FixtureDef myFixtureDef1;
        myFixtureDef1.shape = &polygonShape1; //change the shape of the fixture
        myBodyDef1.position.Set(0,0); 
        b2Body *staticBody1 = world->CreateBody(&myBodyDef1);
        staticBody1->CreateFixture(&myFixtureDef1); //add a fixture to the body

        //2nd polygon
        ....
        //n polygon
    }

The question is how to make the ContactListener know that my polygons are kGameObjectGround?

How you detecting collision? What is not work? Provide code and description of unexpected behavior. — Pavel
I edited the answer, in ContactListener seem to be all okay, maybe I make something in -(void) drawStaticPolygons. Nothing happens when player jumps off the static polygon and nothing if he lands. Class Player initializes with type kGameObjectPlayer, to polygons I set type kGameObjectGround by userData. — user1974123

MrFVD MrFVD · Accepted Answer · 2014-03-31T02:52:21

The problem I see, because i did not check other things, is that the polygon shape does have to be CCW and the vertices don´t look like to be following that rule. Make the vertices in counter clockwise order and should works.

Collision detection Fail in Box2d

1 Answers