b2RopeJoint连接的物体摆动幅度夸张的解决办法——设置线性阻尼

本文链接：https://blog.youkuaiyun.com/yang3wei/article/details/7375037

本文详细介绍了如何在游戏场景中创建动态乌鸦模型，包括物理属性设置、碰撞形状定义、动力学行为模拟以及视觉表现实现。

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/**
 * added by Bruce Yang on 2012.03.09.15.41~
 * 创建乌鸦~
 */
-(b2Body*) createCrow:(BYObject*)object {
    b2Vec2 po = object.position;
    b2BodyDef bodyDef;
    bodyDef.type = b2_dynamicBody;
    bodyDef.position.Set(po.x, po.y);
    b2Body *body = _single.gameSceneWorld->CreateBody(&bodyDef);
    body->SetFixedRotation(true);
    /**
     * https://love2d.org/wiki/Body:getLinearDamping
     * Body:getLinearDamping
     * Gets the linear damping(线性阻尼) of the Body.
     * The linear damping is the rate of decrease of the linear velocity over time. 
     * A moving body with no damping and no external forces will continue moving indefinitely, 
     * as is the case in space. A moving body with damping will gradually stop moving.
     * 
     * Damping is not the same as friction - they can be modelled together. 
     * However, only damping is provided by Box2D (and LOVE).
     */
    /**
     * 2012.03.15.11.20, added by Bruce Yang, adviced by Eric Zhu~
     * 相当的有效啊，乌鸦不再烦人的摆来荡去了~
     */
    body->SetLinearDamping(0.8f);
    body->m_isCuttable = false;
    
    b2PolygonShape shape;
    shape.SetAsBox(0.4f, 0.1f);
    
    b2FixtureDef fixtDef;
    fixtDef.shape = &shape;
    fixtDef.density = CROW_DENSITY;
    fixtDef.friction = CROW_FRICTION;
    fixtDef.restitution = CROW_RESTITUTION;
    body->CreateFixture(&fixtDef);
    
    BYSpriteCrow *sprite = [BYSpriteCrow spriteWithSpriteFrameName:@"animCrow0.png"];
    [sprite setupSchedule];
    sprite.position = ccp(po.x * PTM_RATIO, po.y * PTM_RATIO);
    sprite.tag = TAG_SPRITE_CROW;
    sprite.scale = 1.5f;
    [[BYSingle getInstance] spriteRunRepeatAction:sprite animName:ANIMATION_CACHE_CROW_FLY];
    [_single.gameLayer addChild:sprite z:-1];
    body->SetUserData(sprite);
    return body;
}

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