【COCOS2DX-BOX2D遊戲開發之三】 讀取tiledmap的tmx阻擋
阿新 • • 發佈：2019-01-29
做一款畫素遊戲專案，需要讀取TMX檔案中的阻擋區域，生成box2d的fixture，來做阻擋 使用cocos2dx版本: 2.2.2
1.在tmx檔案中建立一個"Physics"的層，用來存放編輯器中生成的各種阻擋塊
編輯器中主要有polygone, polyline，box和circle4種，其實box也屬於polygone
2.我的tiled map 版本Version 0.9.1
檢視tmx檔案,增加的層屬於<Objectgroup>是不會被渲染的，所以新增多個層對效率也沒有什麼影響, 我們此處叫"Physics"
上圖的4個圖形，分別對應下圖XML的4個<object></object>
polyline讀取一個初始點x,y,然後讀取一些列相對於初始點的偏移值
box讀取x,y,width,height
circle讀取起始點x,y，外加直徑width(height)足以，因為無法構造橢圓的b2Shape，所以我們構造圓
polygon讀取起始點x,y，然後讀取一些列相對於初始點的偏移值，類似於polyline
3.cocos2dx中解析此檔案的時CCTMXXMLParser.cpp 大概在623行，但是程式碼中只解析了polygon,polyline和circle處解析程式碼為空,我們在此處新增完全
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.剩下的就是我們在程式中獲取出這些阻擋區域了
bool Map::createPhysical(b2World *world) { b2BodyDef body_def; body_def.type = b2_staticBody; body_def.position.SetZero(); mBody = world->CreateBody(&body_def); // 找出阻擋區域所在的層 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; // 讀取所有形狀的起始點 float x = ((CCString*)dict->objectForKey("x"))->floatValue(); float y = ((CCString*)dict->objectForKey("y"))->floatValue(); b2Shape* shape = NULL; //多邊形 CCObject *polygon = dict->objectForKey("polygonPoints"); if (polygon) { CCArray *polygon_points = (CCArray*)polygon; std::vector<b2Vec2> points; // 必須將所有讀取的定點逆向，因為翻轉y之後，三角形定點的順序已經逆序了，構造b2PolygonShape會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; } // 相對於起始點的偏移 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; }
附帶上StaticBlockObject程式碼，這個主要用來記錄阻擋的型別、屬性，以後用來做阻擋判斷
/**
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;因為是從程式碼中直接複製的，但無非實現了下面幾個功能：
1.在map中找到"Physics"層
2.遍歷讀取所有圖形的起始點，並分析是何種圖形，並讀取相應的屬性
3.用讀取的每個圖形來構造b2Shape，用地圖的body來構造b2Fixture
其中有幾個地方需要注意：
1.因為Box2d和遊戲中使用的單位不同,分別是米和畫素，所以要用PTM_RATIO巨集來轉換
2.polygon讀取的所有點來構造b2PolygonShape,這個序列必須是讀取的所有點的反向列表，否則會報一個計算center斷言錯誤
產生這個的原因是因為：tmx中的頂點座標系是地圖左上角，遊戲中是左下角，CCTMXXMLParser.cpp中解析起始點的時候，自動幫我們轉為遊戲中的座標
於是tmx中的1，2，3，4的頂點序列，構成的區域是凸多邊形的內部，轉換後就成為了4，3，2，1，構成的是凸多邊形的外部
polyline因為不是閉合的，無所謂逆向一說
std::vector<b2Vec2> points;
// 必須將所有讀取的定點逆向，因為翻轉y之後，三角形定點的順序已經逆序了，構造b2PolygonShape會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;
}
// 相對於起始點的偏移
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.傳個效果圖：
