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

概述http://www.voidcn.com/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 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b

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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

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

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

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

[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     }

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;

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;

5.传个效果图：

总结

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