计算机图形学——OpenGL渲染基础架构二之着色器的使用

水深无声 2022-06-17 02:15 169阅读 0赞

# 计算机图形学——OpenGL渲染基础架构二之着色器的使用 #

## 1、使用步骤 ##

>  *  1.把着色器写到文本文件中，以便在程序中读取调用shader.vert;shader.fragment
>  *  2.用读文件的方式把两个着色器中的代码读到字符串中
>  *  3.新建shader对象，判断创建是否成功glCreateShader()
>  *  4.将着色器字符串关联到shader对象glShaderSource()
>  *  5.编译着色器对象，判断编译是否成功，如果不成功，输出错误日志glCompileShader()
>  *  6.创建着色器程序，判断是否创建成功glCreateProgram()
>  *  7.关联着色器对象和着色器程序glAttachShader()
>  *  8.链接着色器程序，判断链接是否成功glLinkProgram()
>  *  9.使用着色器程序 即让着色器在主程序运行过程中发挥作用glUseProgram()

## 2、使用实例： ##

![20170414121111985][]

Shade.h写成通用的使用的时候直接导入头文件就行

#include <iostream>
    #include <fstream>
    #include <cmath>
    #include <vector>
    #include <string>
    #include <glew.h>
    GLuint loadShaders(const GLchar *vertex_shader_file, const GLchar *fragment_shader_file) {
    
        GLuint vertexShaderID = glCreateShader(GL_VERTEX_SHADER);
        GLuint fragmentShaderID = glCreateShader(GL_FRAGMENT_SHADER);
    
        std::string vertexShaderCode;
        std::ifstream vertexShaderStream(vertex_shader_file, std::ios::in);
        if (vertexShaderStream.is_open()) {
            std::string line = "";
            while (getline(vertexShaderStream, line))
                vertexShaderCode += "\n" + line;
            vertexShaderStream.close();
        } else {
            std::cerr << "Failed to open vertex shader source file." << vertex_shader_file << std::endl;
            return 0;
        }
    
        std::string fragmentShaderCode;
        std::ifstream fragmentShaderStream(fragment_shader_file, std::ios::in);
        if (fragmentShaderStream.is_open()) {
            std::string line = "";
            while (getline(fragmentShaderStream, line))
                fragmentShaderCode += "\n" + line;
            fragmentShaderStream.close();
        } else {
            std::cerr << "Failed to open fragment shader source file." << std::endl;
            return 0;
        }
    
        GLint result = GL_FALSE;
        GLint infoLogLength;
    
        const GLchar *vertexSource = vertexShaderCode.c_str();
        glShaderSource(vertexShaderID, 1, &vertexSource, nullptr);
        glCompileShader(vertexShaderID);
    
        glGetShaderiv(vertexShaderID, GL_COMPILE_STATUS, &result);
        glGetShaderiv(vertexShaderID, GL_INFO_LOG_LENGTH, &infoLogLength);
        if (infoLogLength > 0) {
            std::cout << "VertexShader Error Message:" << std::endl;
            GLchar *vertexShaderErrorMessage = new GLchar[infoLogLength + 1];
            glGetShaderInfoLog(vertexShaderID, infoLogLength, nullptr, vertexShaderErrorMessage);
            std::cout << vertexShaderErrorMessage << std::endl;
            delete [] vertexShaderErrorMessage;
        }
    
        if (!result) {
            std::cerr << "Failed to compile vertex shader." << std::endl;
            return 0;
        }
    
        const GLchar *fragmentSource = fragmentShaderCode.c_str();
        glShaderSource(fragmentShaderID, 1, &fragmentSource, nullptr);
        glCompileShader(fragmentShaderID);
    
        glGetShaderiv(fragmentShaderID, GL_COMPILE_STATUS, &result);
        glGetShaderiv(fragmentShaderID, GL_INFO_LOG_LENGTH, &infoLogLength);
        if (infoLogLength > 0) {
            std::cout << "FragmentShader Error Message:" << std::endl;
            GLchar *fragmentShaderErrorMessage = new GLchar[infoLogLength + 1];
            glGetShaderInfoLog(fragmentShaderID, infoLogLength, nullptr, fragmentShaderErrorMessage);
            std::cout << fragmentShaderErrorMessage << std::endl;
            delete [] fragmentShaderErrorMessage;
        }
    
        if (!result) {
            std::cerr << "Failed to compile fragment shader." << std::endl;
            return 0;
        }
    
        GLuint programID = glCreateProgram();
        glAttachShader(programID, vertexShaderID);
        glAttachShader(programID, fragmentShaderID);
        glLinkProgram(programID);
    
        glGetProgramiv(programID, GL_LINK_STATUS, &result);
        glGetProgramiv(programID, GL_INFO_LOG_LENGTH, &infoLogLength);
        if (infoLogLength > 0) {
            std::cout << "Program Error Message:" << std::endl;
            GLchar *programErrorMessage = new GLchar[infoLogLength + 1];
            glGetProgramInfoLog(programID, infoLogLength, nullptr, programErrorMessage);
            std::cout << programErrorMessage << std::endl;
            delete [] programErrorMessage;
        }
    
        if (!result) {
            std::cerr << "Failed to link program." << std::endl;
            return 0;
        }
    
        glDetachShader(programID, vertexShaderID);
        glDetachShader(programID, fragmentShaderID);
    
        glDeleteShader(vertexShaderID);
        glDeleteShader(fragmentShaderID);
    
        return programID;
    }

// 包含着色器加载库
    #include "shader.h"
    #include <GL/glut.h>
    void draw(){
    	//生成一个VAO
    	GLuint VertexArrayID;  
    	glGenVertexArrays(1,&VertexArrayID);  
    	glBindVertexArray(VertexArrayID); 
    	//顶点信息
    float positionData[]= {  
        -0.6f, -0.6f, 0.0f,  
        0.6f, -0.6f, 0.0f,  
        0.6f, 0.6f, 0.0f };  
    	GLuint vertexbuffer;  
       
    	// Generate 1 buffer,put the resulting identifier in vertexbuffer  
    	glGenBuffers(1, &vertexbuffer);  
    	// The followingcommands will talk about our 'vertexbuffer' buffer  
    	glBindBuffer(GL_ARRAY_BUFFER,vertexbuffer);  
    	// Give our verticesto OpenGL.  
    	glBufferData(GL_ARRAY_BUFFER,sizeof(positionData), positionData, GL_STATIC_DRAW); 
    	
    	//颜色信息
    	float colorData[] = {  
        1.0f, 0.0f, 0.0f,  
        0.0f, 1.0f, 0.0f,  
        0.0f, 0.0f, 1.0f };  
    	// This will identifyour vertex buffer  
    	GLuint colorbuffer;  
       
    	// Generate 1 buffer,put the resulting identifier in vertexbuffer  
    	glGenBuffers(1,&colorbuffer);  
    	// The followingcommands will talk about our 'vertexbuffer' buffer  
    	glBindBuffer(GL_ARRAY_BUFFER,colorbuffer);  
       
    	// Give our verticesto OpenGL.  
    	glBufferData(GL_ARRAY_BUFFER,sizeof(colorData), colorData, GL_STATIC_DRAW);  
    
    	glEnableVertexAttribArray(0);  
    	glBindBuffer(GL_ARRAY_BUFFER,vertexbuffer);  
    	glVertexAttribPointer(  
    	   0,                  // attribute 0. No particularreason for 0, but must match the layout in the shader.  
    	   3,                  // size  
    	   GL_FLOAT,           // type  
    	   GL_FALSE,          // normalized?  
    	   0,                  // stride  
    	   (void*)0            // array buffer offset  
    	);  
    	// 2cond attributebuffer : vertices  
    	glEnableVertexAttribArray(1);  
    	glBindBuffer(GL_ARRAY_BUFFER,colorbuffer);  
    	glVertexAttribPointer(  
    	   1,                  // attribute 1. No particularreason for 0, but must match the layout in the shader.  
    	   3,                  // size  
    	   GL_FLOAT,           // type  
    	   GL_FALSE,           // normalized?  
    	   0,                  // stride  
    	   (void*)0            // array buffer offset  
    	);  
    	glDrawArrays(GL_TRIANGLES,0, 3 );
    }
    void mydisplay(){
    	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //清空颜色和深度缓冲
    	glEnable(GL_DEPTH_TEST);
    	// 创建透视效果视图
    	glMatrixMode(GL_PROJECTION);//对投影矩阵操作
    	glLoadIdentity();//将坐标原点移到中心
    	gluPerspective(90.0f, 1.0f, 1.0f, 20.0f);//设置透视投影矩阵
    	glMatrixMode(GL_MODELVIEW);//对模型视景矩阵操作
    	glLoadIdentity();
    	gluLookAt(0.0, 5.0, -10.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);//视点转换
    	GLuint programID = loadShaders("F:\\大三下课程\\Computer Graphic\\Shader\\ColorArrays.vertexshader", "F:\\大三下课程\\Computer Graphic\\Shader\\ColorArrays.fragmentshader");
    	glUseProgram(programID);
    	draw();
    	glFlush();
    }
    int main(int argc, char *argv[])
    {
    	glewInit();
        glutInit(&argc, argv);
        glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
        glutInitWindowPosition(100, 100);
        glutInitWindowSize(600, 600);
        glutCreateWindow("HelloShader");
    	glewInit(); 
        glutDisplayFunc(&mydisplay);
        glutMainLoop();
        return 0;
    }

顶点着色器文件：

#version 400  
    layout(location = 0)in vec3 VertexPosition;  
    layout(location = 1)in vec3 VertexColor;  
    out vec3 Color;  
    void main()  
    {  
        Color = VertexColor;  
    gl_Position = vec4(VertexPosition,1.0); }

片段着色器：

#version 400  
    in vec3 Color;  
    out vec4 FragColor;  
    void main() {  
        FragColor = vec4(Color, 1.0);  
    }

[20170414121111985]: /images/20220617/5c159877c2984153894b94ff07acd4e9.png