Adding box2d Body on Sprite Cocos2d - ios

Question

I have a bucket in which i want to add box2d body . not on whole bucket but on left, right and bottom so i can throw my ball inside bucket.
Here is my Bucket. I have added box2d body on left and right side of my bucket. like this
It is working fine for me But when i add body on bottom than my game is crashing.
Here is my code for adding 2 body on bucket with comment bottom body as well.
-(b2Body *) createBucket
{
CCSprite* bucket = [CCSprite spriteWithFile:#"simple-bucket-md.png"];
[self addChild:bucket z:3];
b2Body* b_bucket;
//set this to avoid updating this object in the tick schedule
bucket.userData = (void *)YES;
b2BodyDef bodyDef;
bodyDef.type = b2_staticBody;
CGPoint startPos = ccp(400,150);
bodyDef.position = [self toMeters:startPos];
bodyDef.userData = bucket;
bodyDef.gravityScale = 0;
b2PolygonShape dynamicBox;
//----------------------------------
// THis IS body for Left Side
//----------------------------------
int num = 5;
b2Vec2 verts[] = {
b2Vec2(-29.1f / PTM_RATIO, 25.0f / PTM_RATIO),
b2Vec2(-25.4f / PTM_RATIO, -14.9f / PTM_RATIO),
b2Vec2(-18.7f / PTM_RATIO, -14.9f / PTM_RATIO),
b2Vec2(-21.8f / PTM_RATIO, 26.7f / PTM_RATIO),
b2Vec2(-28.9f / PTM_RATIO, 25.1f / PTM_RATIO)
};
dynamicBox.Set(verts, num);
b2FixtureDef fixtureDef;
fixtureDef.shape = &dynamicBox;
fixtureDef.friction = 0.7;
fixtureDef.density = 10.0f;
fixtureDef.restitution = 0.7;
b_bucket = world->CreateBody(&bodyDef);
b_bucket->CreateFixture(&fixtureDef);
//----------------------------------
// THis IS body for Right Side
//----------------------------------
int num1 = 5;
b2Vec2 verts1[] = {
b2Vec2(16.8f / PTM_RATIO, 27.0f / PTM_RATIO),
b2Vec2(15.9f / PTM_RATIO, -11.5f / PTM_RATIO),
b2Vec2(22.1f / PTM_RATIO, -10.7f / PTM_RATIO),
b2Vec2(24.6f / PTM_RATIO, 26.9f / PTM_RATIO),
b2Vec2(16.9f / PTM_RATIO, 26.7f / PTM_RATIO)
};
dynamicBox.Set(verts1, num1);
fixtureDef.shape = &dynamicBox;
b_bucket-> CreateFixture(&fixtureDef);
//----------------------------------
// THis IS body for Bottom
//----------------------------------
/*
int num2 = 5;
b2Vec2 verts2[] = {
b2Vec2(-23.0f / PTM_RATIO, -21.6f / PTM_RATIO),
b2Vec2(18.9f / PTM_RATIO, -21.0f / PTM_RATIO),
b2Vec2(18.2f / PTM_RATIO, -26.1f / PTM_RATIO),
b2Vec2(-22.8f / PTM_RATIO, -25.9f / PTM_RATIO),
b2Vec2(-23.0f / PTM_RATIO, -21.7f / PTM_RATIO)
};
dynamicBox.Set(verts2, num2);
fixtureDef.shape = &dynamicBox;
b_bucket-> CreateFixture(&fixtureDef);
*/
return b_bucket;
}

Answer 1

Your vertices are clockwise ordered, while they should be counter-clockwise.
You must create polygons with a counter clockwise winding (CCW). We must be careful because the notion of CCW is with respect to a right-handed coordinate system with the z-axis pointing out of the plane. This might turn out to be clockwise on your screen, depending on your coordinate system conventions.
Also, in order to create a 4 sides polygon (which it seems what you're trying), you just need 4 vertices. Try something like this.-
int num2 = 4;
b2Vec2 verts2[] = {
b2Vec2(-22.8f / PTM_RATIO, -25.9f / PTM_RATIO),
b2Vec2(18.2f / PTM_RATIO, -26.1f / PTM_RATIO),
b2Vec2(18.9f / PTM_RATIO, -21.0f / PTM_RATIO),
b2Vec2(-23.0f / PTM_RATIO, -21.6f / PTM_RATIO)
};
dynamicBox.Set(verts2, num2);
fixtureDef.shape = &dynamicBox;
b_bucket-> CreateFixture(&fixtureDef);
Notice that you can also remove the fifth vertex of your lateral bodies.