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.fragment2.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：

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); }