前言: 这个系列是我自己在看cocos2dx源码时记录的一些比较重要的数据结构跟方法中间可能穿插些opengl的知识. 每个介绍的类之间没有固定引用顺序,仅作为个人的记录,可能会有点乱(其实主要是为了怕记不住,这次看源码的目的是搞清楚 cocos的MVPMatrix的使用)

#1 CCGLProgram CCGLProgram 是 管理opengl 管线中 GLProgram 和其相关的 着色器, 顶点属性, 统一变量等等的类, 以下是其中几个比较关键的结构体

##1.1 VertextAttrib

VertexAtttrib结构体在数据存储上于 glGetActiveAttrib获取的结构时一致的 index : 指的是vertexShader顶点着色器中 attribute 属性 , 在shader中 可以用(layout=?)指定index size:属性对应类型存储的数量 例如color = {1.0, 1.0, 1.0}, size 为 3, type 为GL_FLOAT type: 指的是属性对应的存储类型 name: 在顶点着色器中属性的名字

/**VertexAttrib is a structure to encapsulate data got from glGetActiveAttrib.*/struct VertexAttrib
{/**Index of attribute, start from 0.*/GLuint index;/**Number of Data type in the attribute, could range from 0-4.*/GLint size;/**Data type of the attribute, could be GL_FLOAT, GL_UNSIGNED_BYTE etc.*/GLenum type;/**The string name in vertex shader.*/std::string name;
};
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这个结构体主要被应用于一下opengl函数的设置

void glVertexAttribPointer( GLuint index, GLint size, GLenum type, GLboolean normalized, GLsizei stride,const GLvoid * pointer);
//GLboolean normalized 属性主要用于标识传入的属性的各个分量是否需要归一化, stride是相同属性的两个数据间的偏移, pointer代表的是属性的首个在buffer里的偏移
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##1.2 Uniform Uniform 主要用于存储 glGetActiveUnifom 和glGetUniformLocation 的数据

/**Uniform is a structure to encapsulate data got from glGetActiveUniform and glGetUniformLocation.*/
struct Uniform
{/**The place where the uniform placed, starts from 0.*/GLint location;/**Number of data type in attribute.*/GLint size;/**Data type of the attribute.*/GLenum type;/**String of the uniform name.*/std::string name;
};
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uniform 统一变量是在一个glprogram 通用的 统一变量空间可以被顶点着色器个片段着色器同时引用 location : 统一变量在glprogram里的位置 ,这个可用的统一变量数是有上限的 size: 相应统一变量的分量数量 type:相应统一变量的数据类型 name:相应统一变量的名字 结构体内容可被用于一下opengl函数

void glUniform*(GLint location,  GLsizei count,  const GLfloat *value)
//count:指明要更改的元素个数。如果目标uniform变量不是一个数组，那么这个值应该设为1；如果是数组，则应该设置为>=1。
//value:指定一个具有count个数值的数组指针，用来更新指定的uniform变量。
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##1.3 VertexIndex 预定义的顶点属性的对应的index, 占坑

/**Enum the preallocated vertex attribute. */enum{/**Index 0 will be used as Position.*/VERTEX_ATTRIB_POSITION,/**Index 1 will be used as Color.*/VERTEX_ATTRIB_COLOR,/**Index 2 will be used as Tex coord unit 0.*/VERTEX_ATTRIB_TEX_COORD,/**Index 3 will be used as Tex coord unit 1.*/VERTEX_ATTRIB_TEX_COORD1,/**Index 4 will be used as Tex coord unit 2.*/VERTEX_ATTRIB_TEX_COORD2,/**Index 5 will be used as Tex coord unit 3.*/VERTEX_ATTRIB_TEX_COORD3,/**Index 6 will be used as Normal.*/VERTEX_ATTRIB_NORMAL,/**Index 7 will be used as Blend weight for hardware skin.*/VERTEX_ATTRIB_BLEND_WEIGHT,/**Index 8 will be used as Blend index.*/VERTEX_ATTRIB_BLEND_INDEX,/**Index 9 will be used as tangent.*/VERTEX_ATTRIB_TANGENT,/**Index 10 will be used as Binormal.*/VERTEX_ATTRIB_BINORMAL,VERTEX_ATTRIB_MAX,// backward compatibilityVERTEX_ATTRIB_TEX_COORDS = VERTEX_ATTRIB_TEX_COORD,};
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##1.4 UniformIndex 预定义的统一变量的对应的index, 占坑. 这里代码用到的枚举名字大家如果有学过opengl的话应该会非常熟悉

 enum{/**Ambient color.*/UNIFORM_AMBIENT_COLOR,/**Projection matrix.*/UNIFORM_P_MATRIX,/**Model view matrix.*/UNIFORM_MV_MATRIX,/**Model view projection matrix.*/UNIFORM_MVP_MATRIX,/**Normal matrix.*/UNIFORM_NORMAL_MATRIX,/**Time.*/UNIFORM_TIME,/**sin(Time).*/UNIFORM_SIN_TIME,/**cos(Time).*/UNIFORM_COS_TIME,/**Random number.*/UNIFORM_RANDOM01,/** @{* Sampler 0-3, used for texture.*/UNIFORM_SAMPLER0,UNIFORM_SAMPLER1,UNIFORM_SAMPLER2,UNIFORM_SAMPLER3,/**@}*/UNIFORM_MAX,};
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##1.4built in shader 内建的shader 字符串

  /**@name Built Shader types@{*//** ETC1 ALPHA supports for 2d */static const char* SHADER_NAME_ETC1AS_POSITION_TEXTURE_COLOR;static const char* SHADER_NAME_ETC1AS_POSITION_TEXTURE_COLOR_NO_MVP;static const char* SHADER_NAME_ETC1AS_POSITION_TEXTURE_GRAY;static const char* SHADER_NAME_ETC1AS_POSITION_TEXTURE_GRAY_NO_MVP;/**Built in shader for 2d. Support Position, Texture and Color vertex attribute.*/static const char* SHADER_NAME_POSITION_TEXTURE_COLOR;/**Built in shader for 2d. Support Position, Texture and Color vertex attribute, but without multiply vertex by MVP matrix.*/static const char* SHADER_NAME_POSITION_TEXTURE_COLOR_NO_MVP;/**Built in shader for 2d. Support Position, Texture vertex attribute, but include alpha test.*///省略一大堆/**Built in shader for camera clear*/static const char* SHADER_CAMERA_CLEAR;/**end of built shader types.@}*/
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##1.5 built in uniform 内建的 uniform 默认名

  /**@name Built uniform names@{*//**Ambient Color uniform.*/static const char* UNIFORM_NAME_AMBIENT_COLOR;/**Projection Matrix uniform.*/static const char* UNIFORM_NAME_P_MATRIX;/**Model view matrix uniform.*/static const char* UNIFORM_NAME_MV_MATRIX;/**Model view projection uniform.*/static const char* UNIFORM_NAME_MVP_MATRIX;/**Normal matrix uniform.*/static const char* UNIFORM_NAME_NORMAL_MATRIX;/**Time uniform.*/static const char* UNIFORM_NAME_TIME;/**Sin time uniform.*/static const char* UNIFORM_NAME_SIN_TIME;/**Cos time uniform.*/static const char* UNIFORM_NAME_COS_TIME;/**Random number uniform.*/static const char* UNIFORM_NAME_RANDOM01;/**@{ Sampler uniform 0-3, used for textures.*/static const char* UNIFORM_NAME_SAMPLER0;static const char* UNIFORM_NAME_SAMPLER1;static const char* UNIFORM_NAME_SAMPLER2;static const char* UNIFORM_NAME_SAMPLER3;/**@}*//**Alpha test value uniform.*/static const char* UNIFORM_NAME_ALPHA_TEST_VALUE;/**end of Built uniform names@}*/
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1.6 built in attribute names

默认的内建属性名字

/**@name Built Attribute names@{*//**Attribute color.*/static const char* ATTRIBUTE_NAME_COLOR;/**Attribute position.*/static const char* ATTRIBUTE_NAME_POSITION;/**@{ Attribute Texcoord 0-3.*/static const char* ATTRIBUTE_NAME_TEX_COORD;static const char* ATTRIBUTE_NAME_TEX_COORD1;static const char* ATTRIBUTE_NAME_TEX_COORD2;static const char* ATTRIBUTE_NAME_TEX_COORD3;/**@}*//**Attribute normal.*/static const char* ATTRIBUTE_NAME_NORMAL;/**Attribute blend weight.*/static const char* ATTRIBUTE_NAME_BLEND_WEIGHT;/**Attribute blend index.*/static const char* ATTRIBUTE_NAME_BLEND_INDEX;/**Attribute blend tangent.*/static const char* ATTRIBUTE_NAME_TANGENT;/**Attribute blend binormal.*/static const char* ATTRIBUTE_NAME_BINORMAL;/**end of Built Attribute names@}*/
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1.7 一些渲染流程管线方法的包装函数

挑选几个可以展示流程的 1.创建glprogram 省略了代码里如何使用内建shader名创建byteArray的过程

bool GLProgram::initWithByteArrays(const GLchar* vShaderByteArray, const GLchar* fShaderByteArray, const std::string& compileTimeDefines)
{_program = glCreateProgram();CHECK_GL_ERROR_DEBUG();// convert defines here. If we do it in "compileShader" we will do it twice.// a cache for the defines could be useful, but seems like overkill at this pointstd::string replacedDefines = "";replaceDefines(compileTimeDefines, replacedDefines);_vertShader = _fragShader = 0;if (vShaderByteArray){if (!compileShader(&_vertShader, GL_VERTEX_SHADER, vShaderByteArray, replacedDefines)){CCLOG("cocos2d: ERROR: Failed to compile vertex shader");return false;}}// Create and compile fragment shaderif (fShaderByteArray){if (!compileShader(&_fragShader, GL_FRAGMENT_SHADER, fShaderByteArray, replacedDefines)){CCLOG("cocos2d: ERROR: Failed to compile fragment shader");return false;}}if (_vertShader){glAttachShader(_program, _vertShader);}CHECK_GL_ERROR_DEBUG();if (_fragShader){glAttachShader(_program, _fragShader);}_hashForUniforms.clear();CHECK_GL_ERROR_DEBUG();return true;
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2.链接

void GLProgram::link()// 内部调用了
//void GLProgram::bindPredefinedVertexAttribs()
//绑定默认的顶点属性
//关键还是这个gl函数
//glBindAttribLocation(_program, attribute_locations[i].location, attribute_locations[i].attributeName);
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3.使用

void GLProgram::use();
//内部实际调用 glUseProgram()
//很奇怪为什么没有dettachshader, 其实链接完就可以释放点shader在cpu端的内存了
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4.更新 这里只找到对uniform统一变量的, MVPMatrix主要就是用uniform传入渲染管线的 网上的说法是cocos管理了一个变换矩阵的堆栈,用于管理和保存需要使用的矩阵数据

void GLProgram::updateUniforms()
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5.其他类似删除释放glprogram , shader内存的包装方法都在源码中很容易找到

#3GLProgramCache 管理所有的GLProgram生死存亡的类

class CC_DLL GLProgramCache : public Ref
{
public:/**Constructor.* @js ctor*/GLProgramCache();/**Destructor.* @js NA* @lua NA*/~GLProgramCache();/** returns the shared instance *//** 怀念的OC风格,现在都没人写OC了吗, 就想知道swift以后会直接兼容C++吗*/static GLProgramCache* getInstance();/** purges the cache. It releases the retained instance. */static void destroyInstance();/** @deprecated Use getInstance() instead */CC_DEPRECATED_ATTRIBUTE static GLProgramCache* sharedShaderCache();/** @deprecated Use destroyInstance() instead */CC_DEPRECATED_ATTRIBUTE static void purgeSharedShaderCache();/** loads the default shaders */void loadDefaultGLPrograms();CC_DEPRECATED_ATTRIBUTE void loadDefaultShaders() { loadDefaultGLPrograms(); }/** reload the default shaders */void reloadDefaultGLPrograms();CC_DEPRECATED_ATTRIBUTE void reloadDefaultShaders() { reloadDefaultGLPrograms(); }/** returns a GL program for a given key *//*使用 对应的char* 变量作为索引 *///例子:GLProgram *p = getGLProgram(GLProgram::SHADER_NAME_POSITION_TEXTURE_COLOR);GLProgram * getGLProgram(const std::string &key);CC_DEPRECATED_ATTRIBUTE GLProgram * getProgram(const std::string &key) { return getGLProgram(key); }CC_DEPRECATED_ATTRIBUTE GLProgram * programForKey(const std::string &key){ return getGLProgram(key); }/** adds a GLProgram to the cache for a given name */void addGLProgram(GLProgram* program, const std::string &key);CC_DEPRECATED_ATTRIBUTE void addProgram(GLProgram* program, const std::string &key) { addGLProgram(program, key); }/** reload default programs these are relative to light */void reloadDefaultGLProgramsRelativeToLights();private:/**@{Init and load predefined shaders.*/bool init();void loadDefaultGLProgram(GLProgram *program, int type);/**@}*//**Get macro define for lights in current openGL driver.*//*获取宏定义的light GLSL方法*/std::string getShaderMacrosForLight() const;/**Predefined shaders.*/std::unordered_map<std::string, GLProgram*> _programs;
};
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PS:第一次写可能像是直接贴代码, 实际也的确如此, 对渲染管线的流程也只是只言片语,不成逻辑,是在抱歉....如果对opengl有兴趣的话可以点击https://learnopengl.com/这里有全套的教程,简单易学.ios 开发可以github上搜索GPUImage项目作为学习opengles2.0的参考