Objective c Box2d Cocos2d转盘与地面接触时发生碰撞

这是我在这里的第一个问题，如果我做错了什么，或者这太长了，很抱歉。我一直在阅读Ray Wenderlich的作品，我对其进行了修改，使其更加平缓，并逐渐走下坡路。基本上我有一个球从崎岖不平的小山上滚下来，但现在球只从上面大约100像素处落下。触摸时，应用程序崩溃（该应用程序是Mac Cocos2d Box2d应用程序）。球码是这样的：

CGSize winSize = [CCDirector sharedDirector].winSize;
self.oeva = [CCSprite spriteWithTexture:[[CCTextureCache sharedTextureCache] addImage:@"Ball.png"]rect:CGRectMake(0, 0, 64, 64)]; 
_oeva.position = CGPointMake(68, winSize.height/2);
[self addChild:_oeva z:1];
b2BodyDef oevaBodyDef;
oevaBodyDef.type = b2_dynamicBody;
oevaBodyDef.position.Set(68/PTM_RATIO, (winSize.height/2)/PTM_RATIO);
// oevaBodyDef.userData = _oeva;
_oevaBody = world->CreateBody(&oevaBodyDef);
b2BodyDef bodyDef;
bodyDef.type = b2_dynamicBody;

bodyDef.position.Set(60/PTM_RATIO, 400/PTM_RATIO);
bodyDef.userData = _oeva;
b2Body *body = world->CreateBody(&bodyDef);

// Define another box shape for our dynamic body.
b2CircleShape dynamicBox;
dynamicBox.m_radius = 70/PTM_RATIO;//These are mid points for our 1m box

// Define the dynamic body fixture.
b2FixtureDef fixtureDef;
fixtureDef.shape = &dynamicBox; 
fixtureDef.density = 1.0f;
fixtureDef.friction = 0.3f;
body->CreateFixture(&fixtureDef);

那很好。这是地形代码，也可以正常工作：

-(void)generateTerrainWithWorld: (b2World *) inputWorld: (int) hillSize;{
b2BodyDef bd;
bd.position.Set(0, 0);

body = inputWorld->CreateBody(&bd);

b2PolygonShape shape;
b2FixtureDef fixtureDef;
currentSlope = 0;

CGSize winSize = [CCDirector sharedDirector].winSize;    
float xf = 0;
float yf = (arc4random() % 10)+winSize.height/3;
int x = 200;
for(int i = 0; i < maxHillPoints; ++i) {
    hillPoints[i] = CGPointMake(xf, yf);
    xf = xf+ (arc4random() % x/2)+x/2;
    yf = ((arc4random() % 30)+winSize.height/3)-currentSlope;
    currentSlope +=10;
}

int hSegments;

for (int i=0; i<maxHillPoints-1; i++) {
    CGPoint p0 = hillPoints[i-1];
    CGPoint p1 = hillPoints[i];
    hSegments = floorf((p1.x-p0.x)/cosineSegmentWidth);
    float dx = (p1.x - p0.x) / hSegments;
    float da = M_PI / hSegments;
    float ymid = (p0.y + p1.y) / 2;
    float ampl = (p0.y - p1.y) / 2;

    CGPoint pt0, pt1;
    pt0 = p0;
    for (int j = 0; j < hSegments+1; ++j) {

        pt1.x = p0.x + j*dx;
        pt1.y = ymid + ampl * cosf(da*j);

        fullHillPoints[fullHillPointsCount++] = pt1;

        pt0 = pt1;
    }        

}

b2Vec2 p1v, p2v;
for (int i=0; i<fullHillPointsCount-1; i++) {
    p1v = b2Vec2(fullHillPoints[i].x/PTM_RATIO,fullHillPoints[i].y/PTM_RATIO);
    p2v = b2Vec2(fullHillPoints[i+1].x/PTM_RATIO,fullHillPoints[i+1].y/PTM_RATIO);
    shape.SetAsEdge(p1v, p2v);
    body->CreateFixture(&shape, 0);
}

错误日志为：

断言失败：（kNormal>1.19209290e-7F），函数b2ContactSolver，文件/Users/coooli01/Documents/Xcode Projects/cococs2d/Hill Slide/Hill Slide/libs/Box2D/Dynamics/Contacts/b2ContactSolver.cpp，第96行

对不起，如果我说得太久了，我已经被困在这个问题上很久了

这种碰撞通常发生在两个物体质量均为零的情况下

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你的地面不需要有质量，因为它是由边缘组成的，但是你的身体应该有质量（通过设置密度）。我看到您正在设置密度，但请确保在碰撞时未更改密度。

这看起来不健康：

for (int i=0; i<maxHillPoints-1; i++) {
    CGPoint p0 = hillPoints[i-1];//first iteration accesses hillPoints[-1]

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for（int i=0；iThanks我现在来看看。非常感谢！我不敢相信导致这次崩溃的唯一原因就是1个数字！如果可以的话我会投赞成票，但我需要更多的声誉。一个掉一个肯定是计算机科学中最常见的错误。
for (int i=0; i<maxHillPoints-1; i++) {
    CGPoint p0 = hillPoints[i-1];//first iteration accesses hillPoints[-1]