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

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<Objectgroup>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<object></object>

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,y,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

 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, "%d", 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", 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, "%d", 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"), "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

 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

 /**
     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

 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：