openGL使用GLFW、GLEW库绘制点

原创

妙为 2022-07-05 09:51:12 博主文章分类：openGL ©著作权

文章标签 OpenGL绘制点 GLFW GLEW 着色器 #include 文章分类 运维

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前言

openGL使用GLFW、GLEW库绘制点，下面这段代码：绘制蓝色背景，中心点是一个黄色的点，由于代码比较简单，所以我把顶点着色器和片元着色器硬编码到c++程序中。问题就在这！！！由于着色器都写在字符串中，造成着色器的错误很难排查。

#include "glew/glew.h"
#include "glfw/glfw3.h"
#include <iostream>

using namespace std;

static const unsigned int scr_width = 800;
static const unsigned int scr_height = 600;

static const int numVAOs = 1;

GLuint renderingProgram;
GLuint vao[numVAOs];

static void error_callback(int error, const char* description)
{
  fprintf_s(stderr, "Error:%s\n", description);
}

static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
  if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
  {
    glfwSetWindowShouldClose(window, GLFW_TRUE);
  }
}

GLuint createShaderProgram()
{
  const char* vShaderSource =
    "#version core 430                \n"
    "void main(void)                \n"
    "{                        \n"
    " gl_Position = vec4(0.f, 0.f, 0.f, 1.f);     \n"
    "}                        \n";

    const char* fShaderSource =
    "#version core 430                \n"
    "out vec4 fragColor;              \n"
    "void main(void)                \n"
    "{                                              \n"
    " fragColor = vec4(1.0f, 1.0f, 0.0f, 1.0f);   \n"
    "}                        \n";

    GLuint vShader = glCreateShader(GL_VERTEX_SHADER);
    GLuint fShader = glCreateShader(GL_FRAGMENT_SHADER);

    glShaderSource(vShader, 1, &vShaderSource, nullptr);
    glShaderSource(fShader, 1, &fShaderSource, nullptr);
    glCompileShader(vShader);
    glCompileShader(fShader);

    GLuint vfProgram = glCreateProgram();
    glAttachShader(vfProgram, vShader);
    glAttachShader(vfProgram, fShader);
    glLinkProgram(vfProgram);

    return vfProgram;
}

void init(GLFWwindow* window)
{
  
  renderingProgram = createShaderProgram();
  //缓冲区最后都会被存入顶点数组对象VAO(Vertex Array Object)
  glGenVertexArrays(numVAOs, vao);
  glBindVertexArray(vao[0]);
}

void display(GLFWwindow* window, double currentTime)
{
  glClearColor(0.f, 0.f, 1.f, 1.f);
  glClear(GL_COLOR_BUFFER_BIT);
  glUseProgram(renderingProgram);
  glPointSize(30.0f);
  glDrawArrays(GL_POINTS, 0, 1);
}


int main(int argc, char** argv)
{
  int glfwState = glfwInit();
  if (GLFW_FALSE == glfwState)
  {
    cout << "GLFW initialize failed. Invoke glfwInit()." << std::endl;
    glfwTerminate();
    exit(EXIT_FAILURE);
  }

  glfwSetErrorCallback(error_callback);

  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
  glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

  GLFWwindow* window = glfwCreateWindow(scr_width, scr_height, "Draw point", nullptr, nullptr);
  if (nullptr == window)
  {
    cout << "GLFW create window failed! Invoke glfwCreateWindow()." << std::endl;
    //释放GLFW所有资源，直到调用glfwInit才能重新获取GLFW资源
    glfwTerminate();
    exit(EXIT_FAILURE);
  }

  //用于设置指定窗口的键回调，在按下、重复或释放键时调用该窗口
  glfwSetKeyCallback(window, key_callback);
  
  //调用线程上指定窗口的OpenGL或OpenGL ES上下文成为当前上下文。上下文一次只能在单个线程上成为当前上下文，并且每个线程一次只能有一个当前上下文。
  glfwMakeContextCurrent(window);
  
  int glewState = glewInit();
  if (GLEW_OK != glewState)
  {
    cout << "GLEW initialize failed! Invoke glfwInit()." << std::endl;
    exit(EXIT_FAILURE);
  }

  //由于这些原因，应用程序通常希望将交换间隔设置为1。可以将其设置为更高的值，但通常不建议这样做，因为这样会导致输入延迟。
  glfwSwapInterval(1);

  init(window);

  while (!glfwWindowShouldClose(window))
  {
    display(window, glfwGetTime());
    glfwSwapBuffers(window);
    glfwPollEvents();
  }

  //销毁窗口,以及撤销窗口事件
  glfwDestroyWindow(window);
  glfwTerminate();
  exit(EXIT_SUCCESS);
  return 0;
}