ios - 在 Sprite Cocos2d 上添加 box2d Body

Question

我有一个桶，我想在其中添加 box2d body 。不是在整个桶上，而是在左边、右边和底部，这样我就可以把球扔进桶里。这是我的桶。我在桶的左侧和右侧添加了 box2d 主体。像这样

它对我来说工作正常但是当我在底部添加 body 时我的游戏崩溃了。

这是我在 bucket 上添加 2 个 body 以及评论 bottom body 的代码。

-(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

您的顶点是顺时针排列的，而它们应该是逆时针排列的。

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.

此外，为了创建一个 4 边形的多边形(这似乎是您正在尝试的)，您只需要 4 个顶点。尝试这样的事情。-

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);

请注意，您还可以删除侧体的第五个顶点。