CCVertexIndexData 主要用于保存实际持有vbo的VertexBuffer 类和 VertexStreanAtrribute 结构体的文件。 #1 VertexData 实际使用的对象

class CC_DLL VertexData : public Ref
{
public:/**Create function, used to create a instance of VertexData.*/static VertexData* create();/**Get the number of streams in the VertexData.*/size_t getVertexStreamCount() const;/**Set a stream to VertexData,given that stream is identified by semantic, so if the semantic is notspecified before, it will add a stream, or it will override the old one.@param buffer The binding buffer of the stream.@param stream The binding vertex attribute, its member semantic will be used as the identifier.*/bool setStream(VertexBuffer* buffer, const VertexStreamAttribute& stream);/**Remove the given streams.@param semantic The semantic of the stream.*/void removeStream(int semantic);/**Get the attribute of stream, const version.@param semantic The semantic of the stream.*/const VertexStreamAttribute* getStreamAttribute(int semantic) const;/**Get the attribute of stream.@param semantic The semantic of the stream.*/VertexStreamAttribute* getStreamAttribute(int semantic);/**Get the binded buffer of the stream.@param semantic The semantic of the stream.*/VertexBuffer* getStreamBuffer(int semantic) const;/**Called for rendering, it will bind the state of vertex data to current rendering pipeline.*/void use();
//.......
protected:/**Simple struct to bundle buffer and attribute.*/struct BufferAttribute{VertexBuffer* _buffer;VertexStreamAttribute _stream;};/**Streams in the VertexData.*/std::map<int, BufferAttribute> _vertexStreams;
};
复制代码

其中除了一系列设置属性获取属性的方法外最重要的就是 _vertexStreams 和 use（）方法 _vertexStreams 保存了持有gl层使用 的顶点缓存对像即vbo的vertexBuffer 和用于glVertexAttributePointer*（）方法的 VertexStreamAttribute 结构体， 实际的使用方法都在use方法内

void VertexData::use()
{uint32_t flags(0);for(auto& element : _vertexStreams){flags = flags | (1 << element.second._stream._semantic);}GL::enableVertexAttribs(flags);int lastVBO = -1;for(auto& element : _vertexStreams){//glEnableVertexAttribArray((GLint)element.second._stream._semantic);auto vertexStreamAttrib = element.second._stream;auto vertexBuffer = element.second._buffer;// don't call glBindBuffer() if not needed. Expensive operation.int vbo = vertexBuffer->getVBO();if (vbo != lastVBO) {glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer->getVBO());lastVBO = vbo;}glVertexAttribPointer(GLint(vertexStreamAttrib._semantic),vertexStreamAttrib._size,vertexStreamAttrib._type,vertexStreamAttrib._normalize,vertexBuffer->getSizePerVertex(),(GLvoid*)((long)vertexStreamAttrib._offset));}
}
复制代码

glVertexAttribPointer方法各参数的意义在之前的日记中有提到过这里就不说明了，会与 对应的vertexStreamAttribute各参数的一同说明

#VertexStreamAttribute 保存了顶点着色器的顶点属性的绑定参数

struct CC_DLL VertexStreamAttribute
{/**Constructor.*/VertexStreamAttribute(): _normalize(false),_offset(0),_semantic(0),_type(0),_size(0){}/**Constructor@param offset The offset of the attribute.@param semantic The semantic (Position, Texcoord, Color etc) of attribute.@param type The type of attribute, could be GL_FLOAT, GL_UNSIGNED_BYTE etc.@param size Describe how many elements of type in the attribute.*/VertexStreamAttribute(int offset, int semantic, int type, int size): _normalize(false),_offset(offset),_semantic(semantic),_type(type),_size(size){}/**Constructor@param offset The offset of the attribute.@param semantic The semantic (Position, Texcoord, Color etc) of attribute.@param type The type of attribute, could be GL_FLOAT, GL_UNSIGNED_BYTE etc.@param size Describe how many elements of type in the attribute.@param normalize If true, the data will be normalized by dividing 255.*/VertexStreamAttribute(int offset, int semantic, int type, int size, bool normalize): _normalize(normalize),_offset(offset),_semantic(semantic),_type(type),_size(size){}/**Whether the attribute should be normalized or not.*/bool _normalize;/**The offset of the attribute in the buffer.*/int _offset;/**Describe that the attribute usage, could be Position, Color etc.这里应该对应的是之前GLProgram里声明的顶点属性名称 枚举里的值*/int _semantic;/**Describe the type of attribute, could be GL_FLOAT, GL_UNSIGNED_BYTE etc.*/int _type;/**Describe how many elements of type in the attribute.*/int _size;
};
复制代码

感觉这个应该放在上面的VertexData的use方法上面说明，应该更合适些 这里估计一种顶点属性就会有一个对应的VertexStreamAttribute 所以如果你需要往顶点shader里传递Position TexCoord 等多个绑定顶点属性时就需要创建多个VertexStreamAttribute， 这些都是在引擎底层实现的使用者基本上不需要去管理

VertexBuffer

实际持有opengl 提供的vbo索引的cocos对象

lass CC_DLL VertexBuffer : public Ref
{
public:/**Create an instance of VertexBuffer.@param sizePerVertex Size in bytes of one vertex.@param vertexNumber The number of vertex.@param usage A hint to indicate whether the vertexBuffer are updated frequently or not to let GL optimise it.*/static VertexBuffer* create(int sizePerVertex, int vertexNumber, GLenum usage = GL_STATIC_DRAW);/**Get the size in bytes of one vertex.*/int getSizePerVertex() const;/**Get the number of vertices.*/int getVertexNumber() const;/**Update all or part of vertices data, if the range specified exceeds the vertex buffer, it will be clipped.@param verts The pointer of the vertex data.@param count The number of vertices to update.@param begin The first vertex to update.*/bool updateVertices(const void* verts, int count, int begin);/**Get the size of the vertex array in bytes, equals getSizePerVertex() * getVertexNumber().*/int getSize() const;/**Get the internal openGL handle.*/GLuint getVBO() const;protected:/**Constructor.*/VertexBuffer();/**Destructor.*/virtual ~VertexBuffer();/**Init the storage of vertex buffer.@param sizePerVertex Size in bytes of one vertex.@param vertexNumber The number of vertex.@param usage A hint to indicate whether the vertexBuffer are updated frequently or not to let GL optimise it.*/bool init(int sizePerVertex, int vertexNumber, GLenum usage = GL_STATIC_DRAW);
protected:/**Event handler for foreground.*/void recreateVBO() const;/**Event listener for foreground.*/EventListenerCustom* _recreateVBOEventListener;
protected:/**Internal handle for openGL.*/mutable GLuint _vbo;/**Size in bytes for one vertex.*/int _sizePerVertex;/**Number of vertices.*/int _vertexNumber;/**Buffer used for shadow copy.*/std::vector<unsigned char> _shadowCopy;/**Hint for optimisation in GL.*/GLenum _usage;
protected:/**Static member to indicate that use _shadowCopy or not. */static bool _enableShadowCopy;
public:/**Static getter for shadowCopy.*/static bool isShadowCopyEnabled() { return _enableShadowCopy; }/**Static setter for shadowCopy.*/static void enableShadowCopy(bool enabled) { _enableShadowCopy = enabled; }
};
复制代码

如果有opengl基础的同学估计看到这些方法的时候就知道这个类是干什么的了

bool VertexBuffer::init(int sizePerVertex, int vertexNumber, GLenum usage/* = GL_STATIC_DRAW*/)
{if(0 == sizePerVertex || 0 == vertexNumber)return false;_sizePerVertex = sizePerVertex;_vertexNumber = vertexNumber;_usage = usage;if(isShadowCopyEnabled()){_shadowCopy.resize(sizePerVertex * _vertexNumber);}glGenBuffers(1, &_vbo);glBindBuffer(GL_ARRAY_BUFFER, _vbo);glBufferData(GL_ARRAY_BUFFER, getSize(), nullptr, _usage);glBindBuffer(GL_ARRAY_BUFFER, 0);return true;
}
复制代码

看到上面init函数的实现后是不是一下子就看懂了，这就是个用来管理对应VBO的管理对象（Cocos中使用了大量这种对象， 基本上使用到的opengl里的handler都有对应的管理对象，就像CCGLProgram）

bool VertexBuffer::updateVertices(const void* verts, int count, int begin)
{if(count <= 0 || nullptr == verts) return false;if(begin < 0){CCLOGERROR("Update vertices with begin = %d, will set begin to 0", begin);begin = 0;}if(count + begin > _vertexNumber){CCLOGERROR("updated vertices exceed the max size of vertex buffer, will set count to _vertexNumber-begin");count = _vertexNumber - begin;}if(isShadowCopyEnabled()){memcpy(&_shadowCopy[begin * _sizePerVertex], verts, count * _sizePerVertex);}glBindBuffer(GL_ARRAY_BUFFER, _vbo);glBufferSubData(GL_ARRAY_BUFFER, begin * _sizePerVertex, count * _sizePerVertex, verts); glBindBuffer(GL_ARRAY_BUFFER, 0);return true;
}
复制代码

上面是VertexBuffer的刷新方法， 绑定对应VBO 使用glsubData类型方法修改VBO缓存中对应区域的数据

#IndexBuffer IndexBuffer 和VertexBuffer实际上功能差不多，但是是用于保存顶点索引缓存的主要用于Mesh等有指定渲染顺序的功能的，它绑定的VBO单独用于保存顶点索引 GL_ELEMENT_ARRAY_BUFFER （并没有在CCVertexIndexData文件中发现IndexData这个类， 可能跟它并不需要使用VertexStreamAttribute类似的结构体的关系吧，虽然这个索引的正确性决定了你最终的渲染结果，可能跟数据量和复杂度有关）