04 Managing shader

版本二：将着色器代码抽到文件当中

老师习惯把着色器文件存在res/shaders/目录下

老师习惯把顶点着色器、片元着色器放在一个文本文件*.shader*当中进行管理

• 因为它们一般成对出现，分成两个文件存，很不直观

例如上一个例子

1. 将顶点着色器、片元着色器放在一个文件当中res/shaders/Basic.shader

#shader vertex
#version 330 core

layout(location = 0) in vec4 position;

void main()
{
    gl_Position = position;
}

#shader fragment
#version 330 core

layout(location = 0) out vec4 color;

void main()
{
    color = vec4(1.0, 0.0, 0.0, 1.0);
}

1. C++代码

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

#define GLEW_STATIC
#include "GL/glew.h"
#include "GLFW/glfw3.h"

struct ShaderProgramSource
{
    std::string VertexSource;
    std::string FragmentSource;
};

static ShaderProgramSource ParseShader(const std::string& filepath)
{
    std::ifstream stream(filepath);

    enum class ShaderType
    {
        NONE = -1, VERTEX = 0, FRAGMENT = 1
    };

    std::string line;
    std::stringstream ss[2];
    ShaderType type = ShaderType::NONE;
    while(getline(stream, line))
    {
        if(line.find("#shader") != std::string::npos)
        {
            if(line.find("vertex") != std::string::npos)
            {
                type = ShaderType::VERTEX;
            }
            else if(line.find("fragment") != std::string::npos)
            {
                type = ShaderType::FRAGMENT;
            }
        }
        else
        {
            ss[(int)type] << line << '\n';
        }
    }

    return {
        ss[0].str(),
        ss[1].str()
    };
}

//...

int main()
{
    //...
    ShaderProgramSource source = ParseShader("res/shaders/Basic.shader");
    //相对路径，在 项目属性>调试>工作目录，设置
    std::cout << source.VertexSource << std::endl;
    std::cout << source.FragmentSource << std::endl;

    unsigned int shader = CreateShader(source.VertexSource, source.FragmentSource);
    glUseProgram(shader);

    while(!glfwWindowShouldClose(window)) {
        //...
    }

    //...

    glDeleteProgram(shader); //删除着色器程序
    return 0;
}