OSG:幼兒園篇 第一章 節點類

一.簡介

 

二.osg::Node 節點類

#include <osg/Node>

 

typedef std::vector<Node*> NodePath;
typedef std::vector<NodePath> NodePathList;
typedef std::vector<Matrix> MatrixList;

class OSG_EXPORT Node : public Object{

public:
  
  Node();
  Node(const Node&, const CopyOp& copyop = CopyOp::SHALLOW_COPY);

  virtual Object* cloneType() const {return new Node();}

  virtual Object* clone(const CopyOp& copyop) const {return new Node(*this, copyop);}

  virtual bool isSamKindAs(const Object* obj) const {return dynamic_cast<const Node*>(obj) != NULL;}

  virtual const char* libraryName() const {return "osg";}

  virtual const char* className() const {return "Node";}

  virtual Node* asNode() {return this;}

  virtual const Node* asNode() const {return this;}

  virtual Drawable* asDrawable() {return 0;}

  virtual const Drawable* asDrawable() const {return 0;}

  virtual Geometry* asGeometry() {return 0;}

  virtual const Geometry* asGeometry() const {return 0;}

  virtual Group* asGroup() {return 0;}

  virtual const Group* asGroup() const {return 0;}

  virtual Transform* asTransform() {return 0;}

  virtual const Transform* asTransform() const {return 0;}

  virtual Camera* asCamera() {return 0;}

  virtual const Camera* asCamera() const {return 0;}

  virtual Switch* asSwitch() {return 0;}

  virtual cosnt Switch* asSwitch() const {return 0;}

  virtual Geode* asGeode() {return 0;}

  virtual const Geode* asGeode() const {return 0;}

  virtual osgTerrain::Terrain* asTerrain() {return 0;}

  virtual void accept(NodeVisitor& nv);
  
  virtual void ascend(NodeVisitor& nv);

  virtual void traverse(NodeVisitor& /*nv*/){}

  typedef std::vector<Group*> ParentList;

  inline const ParentList& getParents() const {return _parents;}

  inline ParentList getParents() {return _parents;}

  inline Group* getParent(unsigned int i) {return _parents[i];}

  inline const Group* getParent(unsigned int i) const {return _parents[i];}

  inline unsigned int getNumParents() const {return static_cast<unsigned int> (_parents.size());}

  NodePathList getParentalNodePaths(osg::Node* haltTraversalAtNode = 0) const;

  Matrixlist getWorldMatrices(const osg::Node* haltTraversalAtNode = 0) const;

  void setUpdateCallback(Callback* nc);

  inline Callback* getUpdateCallback() {return _updateCallback.get();}

  inline const Callback* getUpdateCallback() const {return _updateCallback.get();}

  inline void addUpdateCallback(Callback* nc){
    if(nc != NULL){
      if(_updateCallback.valid())
        _updateCallback->addNestedCallback(nc);
      ele
        setUpdateCallback(nc);
    }
  }

  inline void removeUpdateCallback(Callback* nc){
    if(nc != NULL && _updateCallback.valid()){
      if(_updateCallback == nc)
      {
        ref_ptr<osg::Callback> new_nested_callback = nc->getNestedCallback();
        nc->setNestedCallback(0);
        setUpdateCallback(new_nested_callback.get());
      }
      else
        _updateCallback->remvoeNestedCallback(nc);
    }
  }
 
  inline unsigned int getNumChildrenRequiringUpdateTraversal() const {return _numChildrenRequiringUpdateTraversal;}

  void setEvent

   typedef std::vector<Group*> ParentList;

  // 返回父節點的列表
  const ParentList& getParents() const;

  // 返回指定索引處父節點的指針 
  Group* getParent(unsigned int I);

  // 返回父節點的數目
  unsigned int getNumParents() const;  
};

 

 

三.osg::Group 組節點類

 

osg::Group 組節點類能夠向下繼承有多個 osg::Group 子節點 ，也能夠有多個 osg::Geode 子節點

#include <osg/Group>

 

class OSG_EXPORT Group : public Node{

public:

  Group();
  Group(const Group&, const CopyOp& copyop = CopyOp::SHALLOW_COPY)

  META_Node(osg, Group);

  virtual Group* asGroup()
  virtual const Group* asGroup() consst
 
  virtual void traverse(NodeVisitor& nv)
  
  // 添加一個子節點
  bool addChild(Node* child);

  //向指定索引位置插入一個子節點
  virtual bool insertChild(unsigned int index, Node* child)

  // 刪除一個子節點
  virtual bool removeChild(Node* child);

  //從指定索引位置開始刪除指定數目子節點
  inline bool removeChild(unsigned int pos, unsigned int numChildrenToRemove = 1)

  virtual bool removeChildren(unsigned int pos, unsigned int numChildrenToRemove)

  // 用新的子節點替換一個子節點
  virtual bool replaceChild(Node* origChild, Node* newChild)

  // 返回子節點的數目
  virtual unsigned int getNumChildren() const

  virtual bool setChild(unsigned int i, Node* node)

  //獲取一個指定位置的子節點
  inline Node* getChild(unsigned int i)
  inline const Node* getChild(unsigned int i) const

  // 若是指定節點是一個子節點，返回true
  inline bool containsNode(const Node* node) const

  //獲取一個子節點索引位置
  inline unsigned int getChildIndex(const Node* node) const

  virtual void setThreadSafeRefUnref(bool threadSafe)

  virtual void resizeGLObjectBuffers(unsigned int maxSize)

  virtual void releaseGLObjects(osg::State* = 0) const
  virtual BoundingSphere computeBound() const

protected:

  virtual ~Group()

  virtual void childRemoved(unsigne int /*pos*/, unsigne int /*numChildrenToRemove*/)
  virtual void childInserted(unsigned int /*pos*/)

  NodeList _children; 
    

};

 

 

三.osg::Geode 葉節點類

 osg::Geode 葉節點類用於保存幾何信息以便渲染

osg::Geode 葉節點沒法向下繼承子節點，只能向上繼承 osg::Group 父節點

#include <osg/Geode>

 

class OSG_EXPORT Geode : public Group
{
public:

  //構造函數
  Geode();
  Geode(const Geode&, const CopyOp& copyop = CopyOp::SHALLOW_COPY);


  virtual Geode* asGeode()
  virtual const Geode* asGeode() const

  //從葉節點追加一個可繪製體對象
  virtual bool addDrawable(Drawable* drawable);

  //從葉節點刪除一個可繪製體對象
  virtual bool removeDrawable(Drawable* drawable);
  virtual bool removeDrawables(unsigned int i, unsigned int numDrawablesToRemove = 1)

  //將當前節點中包含的一個可繪製體替換爲新的可繪製體
  virtual bool replaceDrawable(Drawable* origDraw, Drawable* newDraw);

  virtual bool setDrawable(unsigned int i, Drawable* drawable);

  //獲取可繪製體的數目
  inline unsigned int getNumDrawables() const

  //獲取一個指定位置的可繪製體
  inline Drawable* getDrawable(unsigned int i)
  inline const Drawable* getDrawable(unsigned int i) const

  inline bool constainsDrawable(const Drawable* drawable) const

  //獲取一個可繪製體在葉節點的索引位置
  inline unsigned int getDrawableIndex(const Drawable* drawable) const

  void compileDrawables(RenderInfo& renderInfo)
  inline const BoundingBox& getBoundingBox() const
  virtual BoundingSphere computeBound() const;

protected:
  virtual ~Geode();
  mutable osg::BoundingBox _bbox;

};

 

 

四.osg::Geometry 繪圖基元類

在osg中，一般有三種生成幾何體的方法：1.用封裝的OpenGL繪圖基元osg::Geometry，2.是用OSG中預約義的基本幾何體，3.是從文件中導入場景模型

osg::Geometry 幾何體類能夠經過指定頂點 顏色和法線的方式，繪製簡單的線段 三角形 多邊形並將繪圖的結果添加到場景的葉節點Geode中

 

osg::Group* root = new osg::Group();            //組節點
osg::Geode* geode = new osg::Geode();           //葉節點
osg::Geometry* geometry = new osg::Geometry();  //幾何圖元

root->addChild(geode);
geode->addDrawable(geometry);

 

 

五.osg::LOD 細節層次節點類

 osg::LOD節點能夠實現不一樣細節層次下物體的渲染。經過指定各個子節點的有效範圍，該範圍包含了最大和最小值。當子節點與觀察者的距離在這個節點的有效範圍以內時，LOD將顯示這個節點。

基本實現方法：在不影響渲染外觀的前提下，根據場景對象與觀察者的距離，從多個預置方案中選擇一種更爲簡單的方法來表達要渲染的物體，減輕系統繪製場景的負擔，模型越靠近觀察者時越精細。

 

LOD()
bool addChild(Node* child, float min, float max)    //添加一個子節點，並設置對應的觀察距離

//設置指定位置的子節點對應的觀察範圍，或者獲取某個子節點對應的觀察最小值/最大值
void setRange(unsigned int childNo, float min, float max)
float getMinRange(unsigned int childNo) const
float getMaxRange(unsigned int childNo) const

const RangeList& getRangeList() const    //獲取全部子節點觀察範圍的列表

 

 

 

六.osg::Switch 開關節點類

osg::Switch開關節點類能夠渲染或者跳過指定的子節點。根據當前渲染的負荷有選擇地渲染子圖形以實現渲染性能的均衡，或者在界面和層級進行有選擇地切換