1 封装的意义

在之前的demo测试案例中我们可以看到 着色器的代码都是使用字符串来实现的（使用文件会更方便，一般会把顶点和片段着色器储存为两个叫做XXX.vs和XXX.frag的文件），同时编写、编译和管理着色器的步骤较为繁琐。在这里 我们将这些复杂的步骤整合成一个头文件，便于后面更好的操作。该类主要是可以从硬盘读取着色器，然后编译并链接它们，并对它们进行错误检测，这就变得很好用了。

2 封装后的头文件

从文件中 读取shader源码 以及 shader相关编译链接 操作，整合为一个头文件，相关代码后如下所示：

#ifndef SHADER_H
#define SHADER_H

#include <glad/glad.h>

#include <string>
#include <fstream>
#include <sstream>
#include <iostream>

class Shader
{
public:
    unsigned int ID;
    // constructor generates the shader on the fly
    Shader(const char* vertexPath, const char* fragmentPath)
    {
        // 1. retrieve the vertex/fragment source code from filePath
        std::string vertexCode;
        std::string fragmentCode;
        std::ifstream vShaderFile;
        std::ifstream fShaderFile;
        // ensure ifstream objects can throw exceptions:
        vShaderFile.exceptions (std::ifstream::failbit | std::ifstream::badbit);
        fShaderFile.exceptions (std::ifstream::failbit | std::ifstream::badbit);
        try 
        {
            // open files
            vShaderFile.open(vertexPath);
            fShaderFile.open(fragmentPath);
            std::stringstream vShaderStream, fShaderStream;
            // read file's buffer contents into streams
            vShaderStream << vShaderFile.rdbuf();
            fShaderStream << fShaderFile.rdbuf();
            // close file handlers
            vShaderFile.close();
            fShaderFile.close();
            // convert stream into string
            vertexCode   = vShaderStream.str();
            fragmentCode = fShaderStream.str();
        }
        catch (std::ifstream::failure e)
        {
            std::cout << "ERROR::SHADER::FILE_NOT_SUCCESFULLY_READ" << std::endl;
        }
        const char* vShaderCode = vertexCode.c_str();
        const char * fShaderCode = fragmentCode.c_str();
        // 2. compile shaders
        unsigned int vertex, fragment;
        int success;
        char infoLog[512];
        // vertex shader
        vertex = glCreateShader(GL_VERTEX_SHADER);
        glShaderSource(vertex, 1, &vShaderCode, NULL);
        glCompileShader(vertex);
        checkCompileErrors(vertex, "VERTEX");
        // fragment Shader
        fragment = glCreateShader(GL_FRAGMENT_SHADER);
        glShaderSource(fragment, 1, &fShaderCode, NULL);
        glCompileShader(fragment);
        checkCompileErrors(fragment, "FRAGMENT");
        // shader Program
        ID = glCreateProgram();
        glAttachShader(ID, vertex);
        glAttachShader(ID, fragment);
        glLinkProgram(ID);
        checkCompileErrors(ID, "PROGRAM");
        // delete the shaders as they're linked into our program now and no longer necessary
        glDeleteShader(vertex);
        glDeleteShader(fragment);
    }

    // activate the shader
    void use() 
    { 
        glUseProgram(ID); 
    }

    // utility uniform functions
    void setBool(const std::string &name, bool value) const
    {         
        glUniform1i(glGetUniformLocation(ID, name.c_str()), (int)value); 
    }

    void setInt(const std::string &name, int value) const
    { 
        glUniform1i(glGetUniformLocation(ID, name.c_str()), value); 
    }

    void setFloat(const std::string &name, float value) const
    { 
        glUniform1f(glGetUniformLocation(ID, name.c_str()), value); 
    }

private:
    // utility function for checking shader compilation/linking errors.
    void checkCompileErrors(unsigned int shader, std::string type)
    {
        int success;
        char infoLog[1024];
        if (type != "PROGRAM")
        {
            glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
            if (!success)
            {
                glGetShaderInfoLog(shader, 1024, NULL, infoLog);
                std::cout << "ERROR::SHADER_COMPILATION_ERROR of type: " << type << "\n" << infoLog << "\n -- -- " << std::endl;
            }
        }
        else
        {
            glGetProgramiv(shader, GL_LINK_STATUS, &success);
            if (!success)
            {
                glGetProgramInfoLog(shader, 1024, NULL, infoLog);
                std::cout << "ERROR::PROGRAM_LINKING_ERROR of type: " << type << "\n" << infoLog << "\n -- -- " << std::endl;
            }
        }
    }
};
#endif

该系列文章主要参考openGL官网 和学习 learnopenGL官网 进行知识体系的梳理和重构，重在形成自己对openGL知识的理解和知识体系。

• 参考相关链接总站：LearnOpenGL-CN
• 参考OpenGL官网：About The Khronos Group - The Khronos Group Inc
• 同时也参考了网上其他内容知识 进而 进行整合。