Box2D與UIKit - 身體物理

Question

我跟着本教程如何將Box2D添加到我現有的ViewBased應用程序。 http://www.cocoanetics.com/2010/05/physics-101-uikit-app-with-box2d-for-gravity/

現在當我的身體/ UIButton在我的屏幕上方一半時，它向上飛行。當它向下一半時，向下飛行。物理學看起來也不是很現實。我在本教程中構建了我的世界，它的構建方式與本教程中的內容相同（有幾次修改使其與Xcode 4.0兼容）。計時器和機構創建也一樣。任何人都知道什麼是錯的？ （讓我知道如果你需要更多的細節）

這裏是我的身體創建代碼：

// Define the dynamic body. 

b2BodyDef bodyDef; 
bodyDef.type = b2_dynamicBody; 

CGPoint p = physicalView.center; 
CGPoint boxDimensions = CGPointMake(physicalView.bounds.size.width/PTM_RATIO/2.0,physicalView.bounds.size.height/PTM_RATIO/2.0); 

bodyDef.position.Set(p.x/PTM_RATIO, (self.stage.frame.size.height - p.y)/PTM_RATIO); 
bodyDef.userData = (__bridge void *)physicalView; 

// Tell the physics world to create the body 
b2Body *body = world->CreateBody(&bodyDef); 

// Define another box shape for our dynamic body. 
b2PolygonShape dynamicBox; 

dynamicBox.SetAsBox(boxDimensions.x, boxDimensions.y); 

// Define the dynamic body fixture. 
b2FixtureDef fixtureDef; 
fixtureDef.shape = &dynamicBox; 
fixtureDef.density = 3.0f; // 0 is a ball, and 1 is a rock 
fixtureDef.friction = 0.3f; // 0 is a lubercated ball, 1 is rough as sand paper 
fixtureDef.restitution = 0.5f; // 0 is a lead ball, 1 is a super bouncy ball 
body->CreateFixture(&fixtureDef); 

這裏是我設置了世界代碼：

CGSize screenSize = self.stage.bounds.size; 

screenSize.width = 368; 
// Define the gravity vector. 
b2Vec2 gravity; 
gravity.Set(0.0f, -9.81f); 

// Do we want to let bodies sleep? 
// This will speed up the physics simulation 
bool doSleep = false; 

// Construct a world object, which will hold and simulate the rigid bodies. 
world = new b2World(gravity); 
world->SetAllowSleeping(doSleep); 

world->SetContinuousPhysics(true); 

// Define the ground body. 
b2BodyDef groundBodyDef; 
groundBodyDef.position.Set(0, 0); // bottom-left corner 

// Call the body factory which allocates memory for the ground body 
// from a pool and creates the ground box shape (also from a pool). 
// The body is also added to the world. 
b2Body* groundBody = world->CreateBody(&groundBodyDef); 

// Define the ground box shape. 
b2EdgeShape groundBox; 

// bottom 
groundBox.Set(b2Vec2(0,0), b2Vec2(screenSize.width/PTM_RATIO,0)); 
groundBody->CreateFixture(&groundBox, 0); 

// top 
groundBox.Set(b2Vec2(0,screenSize.height/PTM_RATIO), b2Vec2(screenSize.width/PTM_RATIO,screenSize.height/PTM_RATIO)); 
groundBody->CreateFixture(&groundBox, 0); 

// left 
groundBox.Set(b2Vec2(0,screenSize.height/PTM_RATIO), b2Vec2(0,0)); 
groundBody->CreateFixture(&groundBox, 0); 

// right 
groundBox.Set(b2Vec2(screenSize.width/PTM_RATIO,screenSize.height/PTM_RATIO), b2Vec2(screenSize.width/PTM_RATIO,0)); 
groundBody->CreateFixture(&groundBox, 0); 

// a dynamic body reacts to forces right away 
body->SetType(b2_dynamicBody); 

// we abuse the tag property as pointer to the physical body 
physicalView.tag = (int)body; 

Answer 1

問題是我有一個看不見的UIView，它編程地彈出視圖並開始與其他對象碰撞。