OGRE 材質腳本解析的分析

material 08-Default
{
	technique
	{
		pass
		{
			ambient 0.588235 0.588235 0.588235 1
			diffuse 0.588235 0.588235 0.588235 1
			specular 0 0 0 1 10

			texture_unit
			{
				texture liuxing1.bmp
			}
		}

	}

}           
            
 
上述材質腳本，OGRE 解析是在如下函數中 
        
bool ScriptCompiler::compile(const String &str, const String &source, const String &group)
	{
		ScriptLexer lexer;
		ScriptParser parser;
		ConcreteNodeListPtr nodes = parser.parse(lexer.tokenize(str, source));
		return compile(nodes, group);
	}           
        
 
輸入的 str 就是最上邊的材質腳本，已經處理為一個字元串。整個解析分3步。
 
1、lexer.tokenize(str, source))。進行詞法分析，輸出為一個詞數組。結構為：
        
/** This struct represents a token, which is an ID'd lexeme from the
		parsing input stream.
	*/
	struct ScriptToken
	{
		/// This is the lexeme for this token
		String lexeme, file;
		/// This is the id associated with the lexeme, which comes from a lexeme-token id mapping
		uint32 type;
		/// This holds the line number of the input stream where the token was found.
		uint32 line;
	};
	typedef SharedPtr<ScriptToken> ScriptTokenPtr;
	typedef vector<ScriptTokenPtr>::type ScriptTokenList;
	typedef SharedPtr<ScriptTokenList> ScriptTokenListPtr;           
        
 

 處理的字元數組剔除了空格，保留了換行符（10）。處理的字元數組剔除了空格，保留了換行符（10）。處理的字元數組剔除了空格，保留了換行符（10）。
 
2、parser.parse（）。進行類似CST(Concrete Syntax Tree) 分析，輸出為一個文法節點，結構如下：
        
/** The ConcreteNode is the struct that holds an un-conditioned sub-tree of parsed input */
	struct ConcreteNode;
	typedef SharedPtr<ConcreteNode> ConcreteNodePtr;
	typedef list<ConcreteNodePtr>::type ConcreteNodeList;
	typedef SharedPtr<ConcreteNodeList> ConcreteNodeListPtr;
	struct ConcreteNode : public ScriptCompilerAlloc
	{
		String token, file;
		unsigned int line;
		ConcreteNodeType type;
		ConcreteNodeList children;
		ConcreteNode *parent;
	};           
        
 
該文法樹已經剔除了換行符，輸出節點執行個體如下：
 
 
        
material
 
--- 08-Default
 
---{   父節點A
 
---}
 
     父節點A
 
    technique
 
    --- {  父節點B
 
    --- }
 
          父節點B
 
          pass
 
          --- {  父節點C
 
          --- }
 
                 父節點C
 
                 --- ambient 

                      --- 0.588235
 
                      --- 0.588235 

                      --- 0.588235
 
                      --- 1
 
                --- diffuse 

                     --- 0.588235 

                     --- 0.588235  

                     --- 0.588235
 
                     --- 1
 
                --- specular 

                     ---  0
 
                     ---  0
 
                     ---  0
 
                     ---  1
 
                     --- 10
 
                 --- texture_unit
 
                      --- { 父節點D
 
                      --- }
 
                             父節點D 

                              texture
 
                              --- liuxing1.bmp           
        
 

  3、return compile(nodes, group)。實際包含兩步：進行類似AST(Abstract  Syntax Tree) 分析; 之後把AST資訊轉化為Material。
 
 3.1 AST。所用的結構為：
        
class _OgreExport AbstractNode : public AbstractNodeAlloc
	{
	public:
		String file;
		unsigned int line;
		AbstractNodeType type;
		AbstractNode *parent;
		Any context; // A holder for translation context data
	public:
		AbstractNode(AbstractNode *ptr);
		virtual ~AbstractNode(){}
		/// Returns a new AbstractNode which is a replica of this one.
		virtual AbstractNode *clone() const = 0;
		/// Returns a string value depending on the type of the AbstractNode.
		virtual String getValue() const = 0;
	};           
        
 
context 為 Any 類型， 在3.2步根據具體的類型進行相應的轉換。
 它有衆多子類，列舉幾個： 
        
/** This specific abstract node represents a script object */
	class _OgreExport ObjectAbstractNode : public AbstractNode
	{
	private:
		map<String,String>::type mEnv;
	public:
		String name, cls;
		std::vector<String> bases;
		uint32 id;
		bool abstract;
		AbstractNodeList children;
		AbstractNodeList values;
		AbstractNodeList overrides; // For use when processing object inheritance and overriding
	public:
		ObjectAbstractNode(AbstractNode *ptr);
		AbstractNode *clone() const;
		String getValue() const;

		void addVariable(const String &name);
		void setVariable(const String &name, const String &value);
		std::pair<bool,String> getVariable(const String &name) const;
		const map<String,String>::type &getVariables() const;
	};           
        
 
其中 name = "08-Default", cls  即類名 material, id 為該類的标志ID。
        
/** This abstract node represents a script property */
	class _OgreExport PropertyAbstractNode : public AbstractNode
	{
	public:
		String name;
		uint32 id;
		AbstractNodeList values;
	public:
		PropertyAbstractNode(AbstractNode *ptr);
		AbstractNode *clone() const;
		String getValue() const;
	};           
        
 
以及
        
/** This is an abstract node which cannot be broken down further */
	class _OgreExport AtomAbstractNode : public AbstractNode
	{
	public:
		String value;
		uint32 id;
	public:
		AtomAbstractNode(AbstractNode *ptr);
		AbstractNode *clone() const;
		String getValue() const;
	private:
		void parseNumber() const;
	};           
        
 

   
 
經過   AbstractNodeListPtr ast = convertToAST(nodes); 處理後，材質腳本執行個體為
 
  1>  ObjectAbstractNode .
 
          name = "08-Default",  cls="material", id = 3. child 指向下一級, 有1個子節點。
 
  2> ObjectAbstractNode .
 
          name = "",  cls="technique", id = 7. child 指向下一級, 有1個子節點。
 
  3>  ObjectAbstractNode .
 
          name = "",  cls="pass", id = 8. child 指向下一級, 有4個子節點。
 
  4>  PropertyAbstractNode. 有3個，分别為 ambient, diffuse, specular
 
          name = "ambient",   id = 37. values 有4個值，指向下一級。
 
ObjectAbstractNode . 有一個，即紋理
 
name = "", cls="texture_unit", id = 9. child 指向下一級, 有1個子節點, 為PropertyAbstractNode，不再列舉了。
 
5> AtomAbstractNode 
 
value = "0.588235", id = 0.
 
3.2 做了2件事。
 
A 獲得AbstractNode對應的ScriptTranslator：
 
ScriptTranslator *translator = ScriptCompilerManager::getSingleton().getTranslator(*i);
 
B 根據ScriptTranslator 生成 material。注意：生成的material各相關量儲存在AbstractNode的Any類型的變量context中。
 
 
 
CSDN 真垃圾，編輯器現在又亂了，代碼和普通文字已經區分不開。