Box2D Forums

b2BodyDef bodyDefShip;
        bodyDefShip.type = b2_dynamicBody;
        bodyDefShip.userData = self;
        bodyDefShip.position.Set(location.x/PTM_RATIO, location.y/PTM_RATIO);
        shipBody = world->CreateBody(&bodyDefShip);
       
        b2PolygonShape shapeShip;
        shapeShip.SetAsBox(self.contentSize.width/2/PTM_RATIO, self.contentSize.height/2/PTM_RATIO);
       
        b2FixtureDef fixtureDefShip;
        fixtureDefShip.shape = &shapeShip;
        fixtureDefShip.density = 0.0;
        fixtureDefShip.friction = 0.0;
        fixtureDefShip.restitution = 0.0;
       
        shipBody->CreateFixture(&fixtureDefShip);
         
        //for collision detection
        fixtureDefShip.filter.categoryBits = 0x1; //(default is 0x1 so this body belongs to a different category)
        fixtureDefShip.filter.maskBits = 0xFFFF; //(0xFFFF means it collides with all categories)

target = [WeakAndFastShipTarget target];
        //////////////////////////////////BOX2d/////////////////////////////////////////
       
         b2BodyDef bodyDef;
         bodyDef.type = b2_dynamicBody;
         bodyDef.userData = target;
         bodyDef.position.Set(winSize.width/PTM_RATIO, winSize.height/2/PTM_RATIO);
         cometBody = world->CreateBody(&bodyDef);
         
         b2PolygonShape shape;
         shape.SetAsBox(target.contentSize.width/2/PTM_RATIO, target.contentSize.height/2/PTM_RATIO);
         
         b2FixtureDef fixtureDef;
         fixtureDef.shape = &shape;
         fixtureDef.density = 0.0;
         fixtureDef.friction = 0.0;
         fixtureDef.restitution = 0.0;
         
         cometBody->CreateFixture(&fixtureDef);
         
        //for collision detection
        fixtureDef.filter.categoryBits = 0x4; //(default is 0x1 so this body belongs to a different category)
        fixtureDef.filter.maskBits = 0xFFFF; //(0xFFFF means it collides with all categories)

- (void)beginContact:(b2Contact *)contact {
   
    b2Fixture *fixtureA = contact->GetFixtureA();
    b2Fixture *fixtureB = contact->GetFixtureB();
    b2Body *bodyA = fixtureA->GetBody();
    b2Body *bodyB = fixtureB->GetBody();
    GameObject *spriteA = (GameObject *) bodyA->GetUserData();
    GameObject *spriteB = (GameObject *) bodyB->GetUserData();
   
    if (!spriteA.visible || !spriteB.visible) return;
   
    b2WorldManifold manifold;
    contact->GetWorldManifold(&manifold);
    b2Vec2 b2ContactPoint = manifold.points[0];
    CGPoint contactPoint = ccp(b2ContactPoint.x * PTM_RATIO, b2ContactPoint.y * PTM_RATIO);
   
    CGSize winSize = [CCDirector sharedDirector].winSize;
    //////////////////////////////////////////////////////////////////////////SHIP COLLIDES WITH ENEMYSHIP OR ENEMY
    if ((fixtureA->GetFilterData().categoryBits & kCategoryShip && fixtureB->GetFilterData().categoryBits & kCategoryEnemy) ||
        (fixtureB->GetFilterData().categoryBits & kCategoryShip && fixtureA->GetFilterData().categoryBits & kCategoryEnemy)) {
        NSLog(@"Collision happened");
        // Determine enemy ship
        GameObject *enemyShip = (GameObject*) spriteA;
        if (fixtureB->GetFilterData().categoryBits & kCategoryEnemy) {
            enemyShip = spriteB;
        }
        [[SimpleAudioEngine sharedEngine] playEffect:@"explode.caf" pitch:1.0f pan:0.0f gain:0.25f];
                   
        //TAKE A HIT
        [_player takeHit];
    }

#define kCategoryShip 0x1
#define kCategoryShipLaser 0x2
#define kCategoryEnemy 0x4

std::vector<b2Body *>toDestroy;
    std::vector<MyContact>::iterator pos;
    for(pos = _contactListener->_contacts.begin();
        pos != _contactListener->_contacts.end(); ++pos) {
        MyContact contact = *pos;
       
        b2Body *bodyA = contact.fixtureA->GetBody();
        b2Body *bodyB = contact.fixtureB->GetBody();
       
        if (bodyA->GetUserData() != NULL && bodyB->GetUserData() != NULL) {
           
            CCSprite *spriteA = (CCSprite *) bodyA->GetUserData();
            CCSprite *spriteB = (CCSprite *) bodyB->GetUserData();
           
            // If either is Comet && SHIP
            if (([spriteA isKindOfClass:[WeakAndFastShipTarget class]] && [spriteB isKindOfClass:[HopperShip class]]) ||
                ([spriteA isKindOfClass:[HopperShip class]] && [spriteB isKindOfClass:[WeakAndFastShipTarget class]]) ) {
                NSLog(@"COMET HIT SHIP");
                //Call takehit on ship && shake screen && ignore collision force between objects
                //[_player takeHit];
                //if (std::find(toDestroy.begin(), toDestroy.end(), bodyB) == toDestroy.end()) {
                //    toDestroy.push_back(bodyB);
                //}
            }
            // Laser && Comet - this is handled elsewhere
            else if ([spriteA isKindOfClass:[WeakAndFastShipTarget class]] && [spriteA isKindOfClass:[HopperShip class]]) {
                NSLog(@"LASER HIT COMET");
               
                //if (std::find(toDestroy.begin(), toDestroy.end(), bodyA) == toDestroy.end()) {
                //    toDestroy.push_back(bodyB);
                //}
            }     
        }       
    }
    // Clean up array of bodies to destroy?
    std::vector<b2Body *>::iterator pos2;
    for(pos2 = toDestroy.begin(); pos2 != toDestroy.end(); ++pos2) {
        b2Body *body = *pos2;     
        if (body->GetUserData() != NULL) {
            NSLog(@"DESTROY VECTOR");
            CCSprite *sprite = (CCSprite *) body->GetUserData();
            [sceneSpriteBatchNode removeChild:sprite cleanup:YES];
        }
        world->DestroyBody(body);
       
    }
   
    if (toDestroy.size() > 0) {
        NSLog(@"MINECART HIT");
        PLAYSOUNDEFFECT(MINECART_HIT);
    }