【COCOS2DX-BOX2D游戏开发之三】 读取tiledmap的tmx阻挡(转）

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@H_301_1@http://www.jb51.cc/article/p-mpzqadut-xy.html
做一款像素游戏项目，需要读取TMX文件中的阻挡区域，生成Box2d的fixture，来做阻挡 使用cocos2dx版本: 2.2.2

@H_301_1@1.在tmx文件中创建一个”Physics”的层，用来存放编辑器中生成的各种阻挡块
编辑器中主要有polygone,polyline，Box和circle4种，其实Box也属于polygone

@H_301_1@2.我的tiled map 版本Version 0.9.1
查看tmx文件,增加的层属于是不会被渲染的，所以添加多个层对效率也没有什么影响,我们此处叫”Physics”
上图的4个图形，分别对应下图XML的4个

polyline读取一个初始点x,y,然后读取一些列相对于初始点的偏移值
Box读取x,width,height
circle读取起始点x,y，外加直径width(height)足以，因为无法构造椭圆的b2Shape，所以我们构造圆
polygon读取起始点x,y，然后读取一些列相对于初始点的偏移值，类似于polyline

@H_301_1@3.cocos2dx中解析此文件的时CCTMXXMLParser.cpp 大概在623行，但是代码中只解析了polygon,polyline和circle处解析代码为空,我们在此处添加完全

@H_301_1@[cpp] view plain copy 在CODE上查看代码片派生到我的代码片

else if (elementName == "polygon")   
    {  
        // find parent object's dict and add polygon-points to it 
        ObjectGroup* objectGroup = (ObjectGroup*)m_pObjectGroups->lastObject();  
        CCDictionary* dict = (CCDictionary*)objectGroup->getObjects()->lastObject();  

        // get points value string 
        const char* value = valueForKey("points",attributeDict);  
        if(value)  
        {  
            CCArray* pPointsArray = new CCArray;  

            // parse points string into a space-separated set of points 
            stringstream pointsStream(value);  
            string pointPair;  
            while(std::getline(pointsStream,pointPair,' '))  
            {  
                // parse each point combo into a comma-separated x,y point 
                stringstream pointStream(pointPair);  
                string xStr,yStr;  
                char buffer[32] = {0};  

                CCDictionary* pPointDict = new CCDictionary;  

                // set x 
                if(std::getline(pointStream,xStr,','))  
                {  
                    int x = atoi(xStr.c_str()) + (int)objectGroup->getPositionOffset().x;  
                    sprintf(buffer,"%d",x);  
                    CCString* pStr = new CCString(buffer);  
                    pStr->autorelease();  
                    pPointDict->setObject(pStr,"x");  
                }  

                // set y 
                if(std::getline(pointStream,yStr,'))  
                {  
                    int y = atoi(yStr.c_str()) + (int)objectGroup->getPositionOffset().y;  
                    sprintf(buffer,y);  
                    CCString* pStr = new CCString(buffer);  
                    pStr->autorelease();  
                    pPointDict->setObject(pStr,"y");  
                }  

                // add to points array 
                pPointsArray->addObject(pPointDict);  
                pPointDict->release();  
            }  

            dict->setObject(pPointsArray,"points");  
            pPointsArray->release();  

            dict->setObject(dict->objectForKey("points"),"polygonPoints");  
        }  
    }   
    else if (elementName == "polyline")  
    {  
        // find parent object's dict and add polyline-points to it 
        // ObjectGroup* objectGroup = (ObjectGroup*)m_pObjectGroups->lastObject(); 
        // CCDictionary* dict = (CCDictionary*)objectGroup->getObjects()->lastObject(); 
        // TODO: dict->setObject:[attributeDict objectForKey:@"points"] forKey:@"polylinePoints"]; 

        // ------Added by Teng.start 
        // find parent object's dict and add polygon-points to it 
        ObjectGroup* objectGroup = (ObjectGroup*)m_pObjectGroups->lastObject();  
        CCDictionary* dict = (CCDictionary*)objectGroup->getObjects()->lastObject();  

        // get points value string 
        const char* value = valueForKey("points","polylinePoints");  
        }  

        // ------Added by Teng.end 
    }  
    else if (elementName == "ellipse")  
    {  
        // ------Added by Teng.start 
        // Do nothing... 
        ObjectGroup* objectGroup = (ObjectGroup*)m_pObjectGroups->lastObject();  
        CCDictionary* dict = (CCDictionary*)objectGroup->getObjects()->lastObject();  

        CCObject *obj = new CCObject;  
        dict->setObject(obj,"ellipse");  
        obj->release();  
        // ------Added by Teng.end 
    }
@H_301_1@4.剩下的就是我们在程序中获取出这些阻挡区域了
[cpp] view plain copy 在CODE上查看代码片派生到我的代码片

bool Map::createPhysical(b2World *world)  
{  
    b2BodyDef body_def;  
    body_def.type = b2_staticBody;  
    body_def.position.SetZero();  
    mBody = world->CreateBody(&body_def);  

    // 找出阻挡区域所在的层 
    ObjectGroup* group = mTiledMap->objectGroupNamed("Physics");  

    CCArray* array = group->getObjects();  
    CCDictionary* dict;  
    CCObject* pObj = NULL;  
    CCARRAY_FOREACH(array,pObj)  
    {  
        dict = (CCDictionary*)pObj;  
        if (!dict)  
            continue;  

        b2FixtureDef fixture_def;  

        StaticBlockObject *sb_obj = new StaticBlockObject();  

        sb_obj->density = 1.0f;  
        sb_obj->friction = 0.2f;  
        sb_obj->restitution = 0.f;  

        // 读取所有形状的起始点 
        float x = ((CCString*)dict->objectForKey("x"))->floatValue();  
        float y = ((CCString*)dict->objectForKey("y"))->floatValue();  

        b2Shape* shape = NULL;  

        //多边形 
        CCObject *polygon = dict->objectForKey("polygonPoints");  
        if (polygon) {  
            CCArray *polygon_points = (CCArray*)polygon;  

            std::vector<b2Vec2> points;  

            // 必须将所有读取的定点逆向，因为翻转y之后，三角形定点的顺序已经逆序了，构造b2PolygonShape会crash 
            int c =polygon_points->count();  
            points.resize(c);  
            c--;  

            CCDictionary* pt_dict;  
            CCObject* obj = NULL;  
            CCARRAY_FOREACH(polygon_points,obj)  
            {  
                pt_dict = (CCDictionary*)obj;  

                if (!pt_dict) {  
                    continue;  
                }  

                // 相对于起始点的偏移 
                float offx = ((CCString*)pt_dict->objectForKey("x"))->floatValue();  
                float offy = ((CCString*)pt_dict->objectForKey("y"))->floatValue();  

                points[c--] = (b2Vec2((x + offx) / PTM_RATIO,(y-offy) / PTM_RATIO));  
            }  

            b2PolygonShape *ps = new b2PolygonShape();  
            ps->Set(&points[0],points.size());  
            fixture_def.shape = ps;  

            shape = ps;  

            sb_obj->shape = StaticBlockObject::ST_POLYGON;  
        } else if (polygon = dict->objectForKey("polylinePoints")){  
            CCArray *polyline_points = (CCArray*)polygon;  

            std::vector<b2Vec2> points;  

            CCDictionary* pt_dict;  
            CCObject* obj = NULL;  
            CCARRAY_FOREACH(polyline_points,obj)  
            {  
                pt_dict = (CCDictionary*)obj;  

                if (!pt_dict) {  
                    continue;  
                }  

                float offx = ((CCString*)pt_dict->objectForKey("x"))->floatValue();  
                float offy = ((CCString*)pt_dict->objectForKey("y"))->floatValue();  
                points.push_back(b2Vec2((x + offx) / PTM_RATIO,(y-offy) / PTM_RATIO));  
            }  

            b2ChainShape *ps = new b2ChainShape();  
            ps->CreateChain(&points[0],points.size());  
            fixture_def.shape = ps;  

            shape = ps;  

            sb_obj->shape = StaticBlockObject::ST_POLYGON;  
        } else if (dict->objectForKey("ellipse")) {  
            float width = ((CCString*)dict->objectForKey("width"))->floatValue();  
            float height = ((CCString*)dict->objectForKey("height"))->floatValue();  

            b2CircleShape *ps = new b2CircleShape;  
            ps->m_p.Set((x+width/2) / PTM_RATIO,((y+height/2)) / PTM_RATIO);  
            ps->m_radius = width/2/PTM_RATIO;  
            fixture_def.shape = ps;  

            shape = ps;  

            sb_obj->shape = StaticBlockObject::ST_CIRCLE;  
        } else {  
            float width = ((CCString*)dict->objectForKey("width"))->floatValue();  
            float height = ((CCString*)dict->objectForKey("height"))->floatValue();  

            b2PolygonShape *ps = new b2PolygonShape;  
            ps->SetAsBox(width/2/PTM_RATIO,height/2/PTM_RATIO,b2Vec2((x+width/2)/PTM_RATIO,(y+height/2)/PTM_RATIO),0);  
            fixture_def.shape = ps;  

            shape = ps;  

            sb_obj->shape = StaticBlockObject::ST_POLYGON;  

        }  

        fixture_def.density = sb_obj->density;  
        fixture_def.friction = sb_obj->friction;  
        fixture_def.restitution = sb_obj->restitution;  

        b2Fixture *fixture = mBody->CreateFixture(&fixture_def);  
        sb_obj->fixture = fixture;  

        if (shape) {  
            delete shape;  
            shape = NULL;  
        }  

        // Storage the Static block object. 
        mStaticBlockList.push_back(sb_obj);  
    }  

    return true;  
}  

附带上StaticBlockObject代码，这个主要用来记录阻挡的类型、属性，以后用来做阻挡判断
[cpp] view plain copy 在CODE上查看代码片派生到我的代码片
/** Storage fixture user data. use for b2Fixture user data. */  
class iFixtureUserData  
{  
public:  
    typedef uint BodyType;  
    typedef uint FixtureType;  

    static const BodyType   BT_Avata = 0x000;  // no any use... 
    static const FixtureType FT_None = 0x000;  

    static const BodyType BT_Map  = 0x1000;  
    static const FixtureType FT_STATIC_OBJ = 0x1F01;  
    static const FixtureType FT_DYNAMIC_OBJ = 0x1F02;  

    // 
    static const BodyType BT_Role = 0x2000;  
    static const BodyType BT_Bullet = 0x2100;  

    static const FixtureType FT_BODY = 0x2F01;  
    static const FixtureType FT_FOOT = 0x2F02;  


public:  
    iFixtureUserData(BodyType body_type,FixtureType fixture_type):  
        mBodyType(body_type),mFixtureType(fixture_type){  
    }  

    virtual ~iFixtureUserData() {  

    }  

    inline BodyType getBodyType() { return mBodyType; }  
    inline FixtureType getFixtureType() { return mFixtureType; }  

protected:  
    BodyType mBodyType;  
    FixtureType mFixtureType;  
};  

/** Block object. specify a block area in physics engine. */  
class StaticBlockObject : public iFixtureUserData {  
public:  
    StaticBlockObject():  
    iFixtureUserData(BT_Map,FT_STATIC_OBJ),fixture(NULL),half_block(false)  
    {  

    }  
    enum ShapeType {  
        ST_POLYGON = 0,ST_CIRCLE = 1,ST_EDGE = 2  
    };  

    ShapeType shape;        // The shape type. 

    float density;  
    float friction;  
    float restitution;  

    b2Fixture *fixture;  

    bool half_block;  
};  

typedef std::vector<StaticBlockObject *> StaticBlockList;
@H_301_1@因为是从代码中直接复制的，但无非实现了下面几个功能：
1.在map中找到”Physics”层
2.遍历读取所有图形的起始点，并分析是何种图形，并读取相应的属性
3.用读取的每个图形来构造b2Shape，用地图的body来构造b2Fixture
其中有几个地方需要注意：
1.因为Box2d和游戏中使用的单位不同,分别是米和像素，所以要用PTM_RATIO宏来转换
2.polygon读取的所有点来构造b2PolygonShape,这个序列必须是读取的所有点的反向列表，否则会报一个计算center断言错误
产生这个的原因是因为：tmx中的顶点坐标系是地图左上角，游戏中是左下角，CCTMXXMLParser.cpp中解析起始点的时候，自动帮我们转为游戏中的坐标
于是tmx中的1，2，3，4的顶点序列，构成的区域是凸多边形的内部，转换后就成为了4，3，2，1，构成的是凸多边形的外部
polyline因为不是闭合的，无所谓逆向一说
[cpp] view plain copy 在CODE上查看代码片派生到我的代码片

std::vector<b2Vec2> points;  

          // 必须将所有读取的定点逆向，因为翻转y之后，三角形定点的顺序已经逆序了，构造b2PolygonShape会crash 
          int c =polygon_points->count();  
          points.resize(c);  
          c--;  

          CCDictionary* pt_dict;  
          CCObject* obj = NULL;  
          CCARRAY_FOREACH(polygon_points,obj)  
          {  
              pt_dict = (CCDictionary*)obj;  

              if (!pt_dict) {  
                  continue;  
              }  

              // 相对于起始点的偏移 
              float offx = ((CCString*)pt_dict->objectForKey("x"))->floatValue();  
              float offy = ((CCString*)pt_dict->objectForKey("y"))->floatValue();  

              points[c--] = (b2Vec2((x + offx) / PTM_RATIO,(y-offy) / PTM_RATIO));  
          }  

          b2PolygonShape *ps = new b2PolygonShape();  
          ps->Set(&points[0],points.size());  
          fixture_def.shape = ps;
@H_301_1@5.传个效果图：

原文链接：https://www.f2er.com/cocos2dx/339216.html

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