box2d：为什么球可以'；你不会在缓坡上反弹吗？

我创建了一个摩擦为0.f，恢复为1.0的球，如下所示：

// Create shape definition and add to body
    b2FixtureDef ballShapeDef;
    ballShapeDef.shape = &circle;
    ballShapeDef.density = 1.f;
    ballShapeDef.friction = 0.f;
    ballShapeDef.restitution = 1.0f;
    //ballBodyDef.bullet = YES;
    _ballFixture = ballBody->CreateFixture(&ballShapeDef);
    // Give shape initial impulse...
    b2Vec2 force = b2Vec2(0, 1.2f);
    ballBody->ApplyLinearImpulse(force, ballBodyDef.position);

碰撞发生时，球很好地弹离墙壁。但是当它与一个逐渐倾斜的斜坡碰撞时，它会像在冰上一样滑动，就像这样：

// Create shape definition and add to body
    b2FixtureDef ballShapeDef;
    ballShapeDef.shape = &circle;
    ballShapeDef.density = 1.f;
    ballShapeDef.friction = 0.f;
    ballShapeDef.restitution = 1.0f;
    //ballBodyDef.bullet = YES;
    _ballFixture = ballBody->CreateFixture(&ballShapeDef);
    // Give shape initial impulse...
    b2Vec2 force = b2Vec2(0, 1.2f);
    ballBody->ApplyLinearImpulse(force, ballBodyDef.position);

斜坡的物理特性是： 密度：1 摩擦力：0 归还：1

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如何使球反弹离开斜坡？

如果两个表面都没有摩擦力，则当球以一定角度撞击时，没有理由“反弹”。试着让两个表面都有一点摩擦。

试着让球或斜坡恢复原状