cocos2dx - Bypass body contact

Question

I am using cocos2dx and setup two Sprites with same Physics Body definitions see below

PhysicsBody *physicsBody=PhysicsBody::createBox(size,PhysicsMaterial(1.0f,0.0,0.5f),Vec2(0, size.height*0.5));
physicsBody->setGravityEnable(true);
physicsBody->setCategoryBitmask(1);
physicsBody->setCollisionBitmask(1);
physicsBody->setContactTestBitmask(true);
physicsBody->setDynamic(true);
physicsBody->setContactTestBitmask(0xFFFFFFFF);
physicsBody->setMass(5.0f);
node->setPhysicsBody(physicsBody);

I am defining a collision detection between both the physics bodies

auto contactListener=EventListenerPhysicsContactWithBodies::create(player1->getPhysicsBody(), player2->getPhysicsBody());

contactListener->onContactBegin = CC_CALLBACK_1(Game::onPlayerContact, this);

_eventDispatcher->addEventListenerWithSceneGraphPriority(contactListener, this);

I don't want these two bodies to collide with each other or, any effect of physics if they collide. I am doing

bool Game::onPlayerContact(cocos2d::PhysicsContact &contact){
    auto nodeA = contact.getShapeA()->getBody()->getNode();
    auto nodeB = contact.getShapeB()->getBody()->getNode();

    if(nodeA != NULL && nodeB != NULL){

        printf("\nPlayers collided");

    }

    return false;
}

I am not able to bypass the contact between two bodies, what else should be done to avoid collision?

Please Help.

Thanks.

sanchitgulati sanchitgulati · Accepted Answer · 2015-04-14T09:11:32

Collision filtering allows you to prevent collision between shapes. Cocos2d-x supports collision filtering using category and groups bitmasks.

Cocos2d-x supports 32 collision categories. For each shape you can specify which category it belongs to. You also specify what other categories this shape can collide with. This is done with masking bits. For example:

auto sprite1 = addSpriteAtPosition(Vec2(s_centre.x - 150,s_centre.y));
sprite1->getPhysicsBody()->setCategoryBitmask(0x02);    // 0010
sprite1->getPhysicsBody()->setCollisionBitmask(0x01);   // 0001

auto sprite3 = addSpriteAtPosition(Vec2(s_centre.x + 150,s_centre.y + 100),2);
sprite3->getPhysicsBody()->setCategoryBitmask(0x03);    // 0011
sprite3->getPhysicsBody()->setCollisionBitmask(0x03);   // 0011

then in your collision callback. Do this.

if ((shapeA->getCategoryBitmask() & shapeB->getCollisionBitmask()) == 0
   || (shapeB->getCategoryBitmask() & shapeA->getCollisionBitmask()) == 0)
{
   // shapes can't collide
   ret = false;
}

source : http://www.cocos2d-x.org/wiki/Physics

cocos2dx - Bypass body contact

2 Answers