Detecting collision of two bodies, each one has different shape - iphone

Question

I want to detect collision between two bodies, one body has circle shape and another one has convex body (by using vertexes and number of vertexes), and I use contact listener class to detect collision between bodies. I tried detect collision between two circle shapes and it succeeded, but when I tried to detect collision between two bodies (one has convex shape and another one has circle shape) and it failed! even I use tags to identify these bodies.
How can I detect two bodies which have two different shapes (circle and convex)?
ContactListener.h code:
#import "Box2D.h"
class ContactListener : public b2ContactListener
{
private:
void BeginContact(b2Contact* contact);
void EndContact(b2Contact* contact);
};
ContactListener.mm code:
#import "ContactListener.h"
#import "SimpleAudioEngine.h"
#import "cocos2d.h"
void ContactListener::BeginContact(b2Contact* contact) {
b2Body* bodyA = contact->GetFixtureA()->GetBody();
b2Body* bodyB = contact->GetFixtureB()->GetBody();
CCSprite* spriteA = (CCSprite*)bodyA->GetUserData();
CCSprite* spriteB = (CCSprite*)bodyB->GetUserData();
if (spriteA != NULL && spriteB != NULL) {
if (spriteA.tag == 1 && spriteB.tag == 50) { // this is work (two shapes are circles
[[SimpleAudioEngine sharedEngine] playEffect:#"Pin.wav"];
NSLog(#"Contact With Pin is Beginning");
}
if (spriteA.tag == 1 && spriteB.tag == 51) { // this is not work (one is circle shape and another one is convex shape)
[[SimpleAudioEngine sharedEngine] playEffect:#"Jump.wav"];
NSLog(#"Contact With Barrier is Beginning");
}
}
}
void ContactListener::EndContact(b2Contact* contact) {
b2Body* bodyA = contact->GetFixtureA()->GetBody();
b2Body* bodyB = contact->GetFixtureB()->GetBody();
CCSprite* spriteA = (CCSprite*)bodyA->GetUserData();
CCSprite* spriteB = (CCSprite*)bodyB->GetUserData();
if (spriteA != NULL && spriteB != NULL) {
}
}
Tags on above code:
tag of ball (main sprite of game) shape is 1
tag of circle shape is 50
tag of convex shape is 51
Edit:
This is code of object's bodies creation:
#define pinSpriteTag 50
#define barrierSpriteTag 51
#define ballSpriteTag 1
// Creating ball of game (has b2CircleShape)
-(void) createBallOfGameWithPositionX:(int)x yPosition:(int)y radius:(float)radius {
// Put ball on screen
ballOfGameSprite = [CCSprite spriteWithFile:#"GameBall-1-ipad.png"];
ballOfGameSprite.position = ccp(x, y);
[self addChild:ballOfGameSprite z:1 tag: ballSpriteTag];
// Create body of ball
b2BodyDef ballOfGameBodyDef;
ballOfGameBodyDef.type = b2_staticBody;
ballOfGameBodyDef.position.Set(ballOfGameSprite.position.x/PTM_RATIO, ballOfGameSprite.position.y/PTM_RATIO);
ballOfGameBodyDef.userData = ballOfGameSprite;
ballOfGameBody = world->CreateBody(&ballOfGameBodyDef);
// Create Physics properties of ball
b2CircleShape ballOfGameShape;
ballOfGameShape.m_radius = radius/PTM_RATIO;
// Create fixture of ball
b2FixtureDef ballOfGameFixtureDef;
ballOfGameFixtureDef.shape = &ballOfGameShape;
ballOfGameFixtureDef.density = 0.9f;
ballOfGameFixtureDef.friction = 1.0f;
ballOfGameFixtureDef.restitution = 0.9f;
ballOfGameBody->CreateFixture(&ballOfGameFixtureDef);
}
// Creating pin of game (has b2CircleShape)
-(void) createNormalPinOnScreenWithPositionX:(int)x yPosition:(int)y radius:(float)radius {
// Put ball on screen
CCSprite *pin = [CCSprite spriteWithFile:#"GamePinNormal-ipad.png"];
pin.position = ccp(x, y);
[self addChild:pin z:2 tag:pinSpriteTag];
// Create body of ball
b2BodyDef pinBodyDef;
pinBodyDef.type = b2_staticBody;
pinBodyDef.position.Set(pin.position.x/PTM_RATIO, pin.position.y/PTM_RATIO);
pinBodyDef.userData = pin;
b2Body *pinBody = world->CreateBody(&pinBodyDef);
// Create Physics properties of ball
b2CircleShape pinShape;
pinShape.m_radius = radius/PTM_RATIO;
// Create fixture of ball
b2FixtureDef pinFixtureDef;
pinFixtureDef.shape = &pinShape;
pinFixtureDef.density = 0.9f;
pinFixtureDef.friction = 1.0f;
pinFixtureDef.restitution = 0.85f;
pinBody->CreateFixture(&pinFixtureDef);
}
// Creating Barrier of game (has b2PolygonShape)
-(void) createBarrierOnScreenPositionX:(int)x yPosition:(int)y imageName:(NSString *)imageName verts:(b2Vec2*)verts verNum:(int)verNum {
CCSprite *BarrierOfGameSprite = [CCSprite spriteWithFile:imageName];
BarrierOfGameSprite.position = ccp(x, y);
[self addChild:BarrierOfGameSprite z:1 tag:barrierSpriteTag];
b2BodyDef BarrierOfGameBodyDef;
BarrierOfGameBodyDef.type = b2_staticBody;
BarrierOfGameBodyDef.position.Set(BarrierOfGameSprite.position.x/PTM_RATIO, BarrierOfGameSprite.position.y/PTM_RATIO);
BarrierOfGameBodyDef.userData = BarrierOfGameSprite;
b2Body *BarrierOfGameBody = world->CreateBody(&BarrierOfGameBodyDef);
b2PolygonShape BarrierOfGameShape;
BarrierOfGameShape.Set(verts, verNum);
b2FixtureDef BarrierOfGameFixtureDef;
BarrierOfGameFixtureDef.shape = &BarrierOfGameShape;
BarrierOfGameFixtureDef.density = 0.9f;
BarrierOfGameFixtureDef.friction = 1.0f;
BarrierOfGameFixtureDef.restitution = 0.0f;
BarrierOfGameBody->CreateFixture(&BarrierOfGameFixtureDef);
}

Answer 1

Do not detect the collision between two shape.
The best way is to set the object as the userData of the body.
#implemention RigidBody
-(id)init{
...
self.body->userData = self;
}
And then compare the class and address
void beginContact(b2contact contact){
RigidBody *A = (RigidBody*)contact->GetFixtureA()->GetBody()->GetUserData();
if([A isKindOfClass:[RigidBody class]]){
}
// Or
if(self == A){
}
I hope it 's helpful for you.