Box2d and Cocos2d on iOS issues with sprites and positioning - ios

Question

I am creating new sprites/bodies when touching the screen:
-(void) addNewSpriteAtPosition:(CGPoint)pos
{
b2BodyDef bodyDef;
bodyDef.type = b2_dynamicBody;
bodyDef.position=[Helper toMeters:pos];
b2Body* body = world->CreateBody(&bodyDef);
b2CircleShape circle;
circle.m_radius = 30/PTM_RATIO;
// Define the dynamic body fixture.
b2FixtureDef fixtureDef;
fixtureDef.shape=&circle;
fixtureDef.density=0.7f;
fixtureDef.friction=0.3f;
fixtureDef.restitution = 0.5;
body-> CreateFixture(&fixtureDef);
PhysicsSprite* sprite = [PhysicsSprite spriteWithFile:#"circle.png"];
[self addChild:sprite];
[sprite setPhysicsBody:body];
body->SetUserData((__bridge void*)sprite);
}
Here is my positioning helper:
+(b2Vec2) toMeters:(CGPoint)point
{
return b2Vec2(point.x / PTM_RATIO, point.y / PTM_RATIO);
}
PhysicsSprite is the typical one used with Box2D, but I'll include the relevant method:
-(CGAffineTransform) nodeToParentTransform
{
b2Vec2 pos = physicsBody->GetPosition();
float x = pos.x * PTM_RATIO;
float y = pos.y * PTM_RATIO;
if (ignoreAnchorPointForPosition_)
{
x += anchorPointInPoints_.x;
y += anchorPointInPoints_.y;
}
float radians = physicsBody->GetAngle();
float c = cosf(radians);
float s = sinf(radians);
if (!CGPointEqualToPoint(anchorPointInPoints_, CGPointZero))
{
x += c * -anchorPointInPoints_.x + -s * -anchorPointInPoints_.y;
y += s * -anchorPointInPoints_.x + c * -anchorPointInPoints_.y;
}
self.position = CGPointMake(x, y);
// Rot, Translate Matrix
transform_ = CGAffineTransformMake(c, s, -s, c, x, y);
return transform_;
}
Now, I have two issues illustrated by the following two images, which show the debug draw with the sprites. Retina and non-retina versions:
Issue #1 - As you can see in both images, the further away from (0,0) the objects are, the sprite becomes further offset from the physics body.
Issue #2 - The red circle image files are 60x60 (retina), and the white circles are 30x30 (non-retina). Why are they sized differently on screen? Cocos2d should use points, not pixels, so shouldn't they be the same size on screen?

Answer 1

Instead of hardcoded size, use contentSize.
circle.m_radius = sprite.contentSize.width*0.5f/PTM_RATIO;
This works in all SD and Retina mode.
You can use this style to sync between box2d and cocos2d positions:
body->SetTransform([self toB2Meters:sprite.position], 0.0f); //box2d<---cocos2d
//OR
sprite.position = ccp(body->GetPosition().x * PTM_RATIO,
body->GetPosition().y * PTM_RATIO); //box2d--->cocos2d