objective-c - Box2d Cocos2d 圆与地面接触时崩溃

Question

这是我在这里的第一个问题，很抱歉，如果我做错了什么或者这太长了。我一直在阅读this tutorial作者 Ray Wenderlich，我对其进行了修改，使其更平坦并逐渐下坡。基本上我有一个球从颠簸的山上滚下来，但目前球只从上方大约 100 像素下降。当触摸应用程序崩溃时(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);

这很好用。这是地形代码，这也可以正常工作:

-(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);
}

}

但是，当两者发生碰撞时，应用程序就会崩溃。崩溃错误是:

Thread 6 CVDisplayLink: Program received signal: "SIGABRT"

错误发生在 b2ContactSolver.cpp 的第 96 行:

b2Assert(kNormal > b2_epsilon);

错误日志是:

Assertion failed: (kNormal > 1.19209290e-7F), function b2ContactSolver, file /Users/coooli01/Documents/Xcode Projects/Cocos2d/Hill Slide/Hill Slide/libs/Box2D/Dynamics/Contacts/b2ContactSolver.cpp, line 96.

对不起，如果我漫无目的地说得太久了，我已经被困在这个问题上很多年了。

Answer 1

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]

除此之外，它对我来说还可以(只是猜测这里没有给出的一些值)。