c++ - 如何使用 Box2D 分配器？

Question

这里有两个问题。首先，如果我需要在 Clone 之前创建 b2BlockAllocator 然后在克隆之后删除(在哪里？)？ Xcode 分析工具未显示 C++ 泄漏...

b2FixtureDef fixd = fix->fixture;
const b2Shape *shape = fixd.shape;
if(shape->GetType()== b2Shape::e_polygon && flip)
{
    b2PolygonShape* ps = (b2PolygonShape*)shape->Clone(new b2BlockAllocator());
    for(int i=0;i<ps->m_vertexCount;i++)
    {
        ps->m_vertices[i].x *= -1;
        ps->m_vertices[i].y *= -1;
    }

    ps->Set(&ps->m_vertices[0], ps->m_vertexCount);
    body->CreateFixture(ps, 1.0f);
...

在这段代码中，我获取缓存的形状对象，克隆它，修改顶点，设置计算法线并将它的对象分配给 body 。问题 - 这合法吗？

更新:

-(void) addFixturesToBody:(b2Body*)body forShapeName:(NSString*)shapeName flip:(BOOL)flip
{
    BodyDef *so = [shapeObjects_ objectForKey:shapeName];
    assert(so);

    FixtureDef *fix = so->fixtures;
    while(fix)
    {
        b2FixtureDef fixd = fix->fixture;
        const b2Shape *shape = fixd.shape;
        if(shape->GetType()== b2Shape::e_polygon && flip)
        {
            b2BlockAllocator allocator;
            b2PolygonShape* ps = (b2PolygonShape*)shape->Clone(&allocator);
            for(int i=0;i<ps->m_vertexCount;i++)
            {
                ps->m_vertices[i].x *= -1;
                ps->m_vertices[i].y *= -1;
            }

            ps->Set(&ps->m_vertices[0], ps->m_vertexCount);
            body->CreateFixture(ps, 1.0f);
        }
        else
        {
            NSLog(@"noflip...%@", shapeName);
            body->CreateFixture(&fix->fixture);
        }
        fix = fix->next;
    }
}

Answer 1

我在试图找到类似答案时晚了 4 年才回复。似乎很少有人在 Box2D 上付出更多努力。

因此，您肯定在泄漏，因为 new b2BlockAllocator 不会在任何地方被删除，无论是您还是 Clone 函数。

只需创建一个本地 b2BlockAllocator，以便在超出范围时将其销毁。就是这样。

    b2BlockAllocator cloneHelper;
    b2PolygonShape* ps = (b2PolygonShape*)shape->Clone(&cloneHelper);