openGL Shader

//! add shader to shader program
static void AddShader(GLuint ShaderProgram, const char* pShaderText, GLenum ShaderType)
{
    GLuint ShaderObj = glCreateShader(ShaderType);                                         //! 1. glCreateShader 创建shader

    if (ShaderObj == 0) {
        fprintf(stderr, "Error creating shader type %d\n", ShaderType);
        exit(0);
    }

    const GLchar* p[1];
    p[0] = pShaderText;
    GLint Lengths[1];
    Lengths[0]= strlen(pShaderText);
    glShaderSource(ShaderObj, 1, p, Lengths);                                               //! 2. glShaderSource  装载shader内容
    glCompileShader(ShaderObj);                                                             //! 3. glCompileShader 编译shader

    GLint success;
    glGetShaderiv(ShaderObj, GL_COMPILE_STATUS, &success);
    if (!success) {
        GLchar InfoLog[1024];
        glGetShaderInfoLog(ShaderObj, 1024, NULL, InfoLog);
        fprintf(stderr, "Error compiling shader type %d: '%s'\n", ShaderType, InfoLog);
        exit(1);
    }

    glAttachShader(ShaderProgram, ShaderObj);                                               //! 4. glAttachShader  附加shader到program
}

static void CompileShaders()
{
    GLuint ShaderProgram = glCreateProgram();                                               //! glCreateProgram 创建shaderProgram

    if (ShaderProgram == 0) {
        fprintf(stderr, "Error creating shader program\n");
        exit(1);
    }
    
    string vs, fs;

    if (!ReadFile(pVSFileName, vs)) {                 
        exit(1);
    };

    if (!ReadFile(pFSFileName, fs)) {
        exit(1);
    };

    AddShader(ShaderProgram, vs.c_str(), GL_VERTEX_SHADER);                                 //! add vertex shader to program
    AddShader(ShaderProgram, fs.c_str(), GL_FRAGMENT_SHADER);                               //! add fragment shader to program

    GLint Success = 0;
    GLchar ErrorLog[1024] = { 0 };

    glLinkProgram(ShaderProgram);                                                           //! glLinkProgram 链接 program
    glGetProgramiv(ShaderProgram, GL_LINK_STATUS, &Success);             
    if (Success == 0) {
        glGetProgramInfoLog(ShaderProgram, sizeof(ErrorLog), NULL, ErrorLog);
        fprintf(stderr, "Error linking shader program: '%s'\n", ErrorLog);
        exit(1);
    }

    glValidateProgram(ShaderProgram);                                                       //! check Validate
    glGetProgramiv(ShaderProgram, GL_VALIDATE_STATUS, &Success);
    if (!Success) {
        glGetProgramInfoLog(ShaderProgram, sizeof(ErrorLog), NULL, ErrorLog);
        fprintf(stderr, "Invalid shader program: '%s'\n", ErrorLog);
        exit(1);
    }

    glUseProgram(ShaderProgram);                                                             //! 使用该 program
}

渲染管线过程：