【十八，封装shader】

在以往的学习中简单列举了下需要封装的shade功能，趁着重构代码，将封装后的shader类添加到项目工程里。

• 头文件

#ifndef shader_hpp
#define shader_hpp

#include <stdio.h>
#include <string>

namespace LEARN_OPEN_GL {
    class Shader {
    public:
        unsigned int ID;
        Shader(const char *vertexPath, const char *fragmentPath);
        void use();
        void setBool(const std::string &name, bool value) const;
        void setInt(const std::string &name, bool value) const;
        void setFloat(const std::string &name, float value) const;
    private:
        void checkCompileErrors(unsigned int shader, std::string type);
    };
}

#endif /* shader_hpp */

头文件定义了构造函数、检查错误函数、使用函数和修改uniform值得函数，其中构造函数需要传入顶点着色器和片段着色器的文件路径。

• 实现如下

#include "shader.h"
#include <glad/glad.h>
#include <fstream>
#include <sstream>
#include <iostream>
#include "const.h"

using namespace LEARN_OPEN_GL;

Shader::Shader(const char *vertexPath, const char *fragmentPath) {
    std::string vertexCode;
    std::string fragmentCode;
    std::ifstream vShaderFile;
    std::ifstream fShaderFile;
    vShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);
    fShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);
    try{
        vShaderFile.open(vertexPath);
        fShaderFile.open(fragmentPath);
        std::stringstream vShaderStream, fShaderStream;
        vShaderStream<<vShaderFile.rdbuf();
        fShaderStream<<fShaderFile.rdbuf();
        vShaderFile.close();
        fShaderFile.close();
        
        vertexCode = vShaderStream.str();
        fragmentCode = fShaderStream.str();
    }
    catch(std::ifstream::failure e) {
        std::cout<<"error shader file not successfully read "<<std::endl;
    }
    
    const char *vShaderCode = vertexCode.c_str();
    const char *fShaderCode = fragmentCode.c_str();
    
    unsigned int vertex, fragment;
    
    vertex = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertex, 1, &vShaderCode, NULL);
    glCompileShader(vertex);
    checkCompileErrors(vertex, "VERTEX");
    
    fragment = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragment, 1, &fShaderCode, NULL);
    glCompileShader(fragment);
    checkCompileErrors(fragment, "FRAGMENT");
    
    ID = glCreateProgram();
    glAttachShader(ID, vertex);
    glAttachShader(ID, fragment);
    glLinkProgram(ID);
    checkCompileErrors(ID, "PROGRAM");
    
    glDeleteShader(vertex);
    glDeleteShader(fragment);
}

void Shader::use()
{
    glUseProgram(ID);
}

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

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

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

void Shader::checkCompileErrors(unsigned int shader, std::string type)
{
    int success;
    char infoLog[LOG_INFO_LEN];
    GLenum pName = GL_COMPILE_STATUS;
    
    if (type != "PROGRAM") {
        glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
        if (!success) {
            glGetShaderInfoLog(shader, LOG_INFO_LEN, NULL, infoLog);
            std::cout<<"Check compile error : "<<type<<" , info:"<<infoLog<<std::endl;
        }
    } else {
        glGetProgramiv(shader, GL_LINK_STATUS, &success);
        if (!success) {
            glGetProgramInfoLog(shader, LOG_INFO_LEN, NULL, infoLog);
            std::cout<<"Check compile error : "<<type<<" , info:"<<infoLog<<std::endl;
        }
    }
    
}

• 着色器重构
  现在我们可以把着色器的代码放入到文件中了，如下图：

1. 顶点着色器以.vs为后缀；
2. 片段着色器以.fs为后缀；
3. 0_common. 是绘制普通三角形的着色器；1_withColor. 是绘制顶点带颜色的三角形的

• 代码的重构

1. 删除const.h中关于着色器的字符串;
2. 封装的render类中去除关于着色器的编译代码；
3. 使用Shader类的对象进行着色器相关的处理。

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封装shader后的代码