opengl 几何着色器

绘制4条线段

 #define GLEW_STATIC
 #include <GL/glew.h>
 #include <GLFW/glfw3.h>

 #include "Shader.h"
 #include <fstream>
 #include <iostream>
 using namespace std;

 void framebuffer_size_callback(GLFWwindow* window, int width, int height);
 void processInput(GLFWwindow *window);

 // settings
 const unsigned int SCR_WIDTH = ;
 const unsigned int SCR_HEIGHT = ;

 // timing
 float deltaTime = 0.0f;
 float lastFrame = 0.0f;

 int main()
 {
     // glfw: initialize and configure
     // ------------------------------
     glfwInit();
     glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, );
     glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, );
     glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

 #ifdef __APPLE__
     glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // uncomment this statement to fix compilation on OS X
 #endif

                                                          // glfw window creation
                                                          // --------------------
     GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
     if (window == NULL)
     {
         std::cout << "Failed to create GLFW window" << std::endl;
         glfwTerminate();
         return -;
     }
     glfwMakeContextCurrent(window);
     glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

     glewExperimental = GL_TRUE;
     if (glewInit() != GLEW_OK)
     {
         cout << "Failed to initialize GLEW!" << endl;
         return -;
     }
     // configure global opengl state
     // -----------------------------

     Shader shader("E:\\C++\\High_level_GLSL\\2.1ver1.txt", "E:\\C++\\High_level_GLSL\\2.1frag1.txt",
         "E:\\C++\\High_level_GLSL\\2.1geo1.txt");

     float points[] = {
         -0.5f, 0.5f,
         0.5f, 0.5f,
         0.5f, -0.5f,
         -0.5f, -0.5f
     };

     /*float points[] = {
         -0.5f, 0.5f, 1.0f, 0.0f, 0.0f,
         0.5f, 0.5f, 0.0f, 1.0f, 0.0f,
         0.5f, -0.5f, 0.0f, 0.0f, 1.0f,
         -0.5f, -0.5f, 1.0f, 1.0f, 0.0f
     };*/

     unsigned int VAO, VBO;
     glGenVertexArrays(, &VAO);
     glGenBuffers(, &VBO);
     glBindVertexArray(VAO);
     glBindBuffer(GL_ARRAY_BUFFER, VBO);
     glBufferData(GL_ARRAY_BUFFER, sizeof(points), &points, GL_STATIC_DRAW);
     glEnableVertexAttribArray();
     glVertexAttribPointer(, , GL_FLOAT, GL_FALSE,  * sizeof(float), (void*));
     //glEnableVertexAttribArray(1);
     //glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(2 * sizeof(float)));
     glBindVertexArray();

     while (!glfwWindowShouldClose(window))
     {
         processInput(window);

         glClearColor(0.1f, 0.1f, 0.1f, 1.0f);
         glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

         shader.use();
         glBindVertexArray(VAO);
         glDrawArrays(GL_POINTS, , );

         glfwSwapBuffers(window);
         glfwPollEvents();
     }

     glDeleteVertexArrays(, &VAO);
     glDeleteBuffers(, &VBO);

 }

     void processInput(GLFWwindow *window)
     {
         if (glfwGetKey(window, GLFW_KEY_ENTER) == GLFW_PRESS)
             glfwSetWindowShouldClose(window, true);
     }

     // glfw: whenever the window size changed (by OS or user resize) this callback function executes
     // ---------------------------------------------------------------------------------------------
     void framebuffer_size_callback(GLFWwindow* window, int width, int height)
     {
         // make sure the viewport matches the new window dimensions; note that width and
         // height will be significantly larger than specified on retina displays.
         glViewport(, , width, height);
     }

E:\\C++\\High_level_GLSL\\2.1ver1.txt

 #version  core
 layout (location = ) in vec2 aPos;

 void main()
 {
     gl_Position = vec4(aPos, 0.0f, 1.0f);
 }

E:\\C++\\High_level_GLSL\\2.1frag1.txt

 #version  core
 out vec4 FragColor;
 void main()
 {
     FragColor = vec4(0.0f, 1.0f, 0.0f, 1.0f);
 }

E:\\C++\\High_level_GLSL\\2.1geo1.txt

 #version  core
 layout (points) in;
 layout (line_strip, max_vertices = ) out;

 void main()
 {
     gl_Position = gl_in[].gl_Position + vec4(-0.1f, 0.0f, 0.0f, 0.0f);
     EmitVertex();
     gl_Position = gl_in[].gl_Position + vec4(0.1f, 0.0f, 0.0f, 0.0f);
     EmitVertex();

     EndPrimitive();
 }

Shader.h头文件，只需将链接里的#include <glad/glad.h>换成　　

#define GLEW_STATIC
#include <GL/glew.h>

就行