C++ opengl/glut中的renderDisplayFunc多次调用myfunc #包括“GL/glut.h” #包括“总账/总账h” #包括 #包括 使用名称空间std； #定义XWidth 700//剪裁窗口大小700*700 #定义YHeight 700 void renderFunction（）{ /*清除上次绘制的信息 设置用于清除的当前清除颜色 RGBA模式下的颜色缓冲区。 */ glClearColor（0.0,0.0,0.0,0.0）； glClear（GLU颜色缓冲位）； //设置线宽 线宽（1）； //（x，y）以像素为单位的坐标 glMatrixMode（GL_投影）； glLoadIdentity（）； 格洛托（0，XWidth，0，YHeight，-1，1）； //设置线条颜色 GL3F（1.0,0.0,0.0）； //随机数生成 对于（inti=0；i

，我在这里看到了几个问题

较小的一个是，在

renderFunction

中缩进for循环有点误导。该循环始终有4次迭代，每次打印一次随机变量

第二个问题是，您似乎误解了glutDisplayFunc（renderFunction）；的含义。如前所述，这仅将glut的默认“显示”回调注册为

renderFunction

，并且：

GLUT根据窗口的重新显示状态确定何时触发显示回调

将调用已注册的回调，直到程序完成。请注意，

glutMainLoop

永远不会返回。程序被未处理的信号或主窗口关闭中断。这意味着，如果最小化并还原窗口，glut将希望重新绘制其内容，并将调用显示回调（

renderFunction

）再次

由于您无法轻松控制，或者不应该尝试控制glut何时调用显示函数，因此我建议您确保显示函数只在屏幕上绘制。您可以生成（和打印）

main

函数中的随机值，并且随机变量是全局的，以便可以从

renderFunction

轻松访问。或者，通过条件语句保护采样和打印的执行，条件语句在第一次执行时修改标志：

#include "GL/glut.h"
#include "GL/gl.h"
#include <iostream>
#include <stdlib.h>

using namespace std;

#define XWidth 700  // Clipping window size 700*700
#define YHeight 700 

void renderFunction() {

/*Clear Information from last draw
Sets the current clearing color for use in clearing
color buffers in RGBA mode.
*/
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glClear(GL_COLOR_BUFFER_BIT);

    //Set line width
    glLineWidth(1);

    //(x,y) coordinates as in pixels
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, XWidth, 0, YHeight, -1, 1);


    //Set line color
    glColor3f(1.0, 0.0, 0.0);

    //random num generated
    for(int i=0;i<4;i++){
    int r1 = rand() % 1000;
    int r2 = rand() % 1000;
    int r3 = rand() % 1000;
    int r4 = rand() % 1000;

    //Begin LINE coordinates
    glBegin(GL_LINES);
        glVertex2d(r1, r2);
        glVertex2d(r3,r4);
    //End LINE coordinate
    glEnd();
    cout<<r1<<" "<<r2<<" "<<r3<<" "<<r4<<" i is "<<i<<endl;}

    //Forces previously issued OpenGL commands to begin execution
    glFlush();
}

// Driver program to test above functions
int main(int argc, char** argv) {

    //Initialize GLUT
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE);

    //Set Output Window Size
    glutInitWindowSize(XWidth,YHeight);

    //Set the position of Output window corresponding to Screen
    glutInitWindowPosition(100,100);

    //Create the Window
    glutCreateWindow("OpenGL - Classify line among three classes");

    //Set handler functions for drawing
    glutDisplayFunc(renderFunction);

    //Start the main loop
    glutMainLoop();
    return 0;
}

在任何一种情况下，您都需要存储所有16个随机变量，因为您将4次生成4个随机值（并且您将所有这些值都用于绘图/打印）。我建议将它们存储在

int r[4][4]；

以下是我的首选版本：

// at global scope (before renderFunction)
generated = false
declare random variables
...
// inside renderFunction 
if (generated = false) {
  generate RV
  print RV
  generated = true
}
display lines

#包括“GL/glut.h”
#包括“总账/总账h”
#包括
#包括
使用名称空间std；
#定义XWidth 700//剪裁窗口大小700*700
#定义YHeight 700
int r[4][4]；
void renderFunction（）{
/*清除上次绘制的信息
设置用于清除的当前清除颜色
RGBA模式下的颜色缓冲区。
*/
glClearColor（0.0,0.0,0.0,0.0）；
glClear（GLU颜色缓冲位）；
//设置线宽
线宽（1）；
//（x，y）以像素为单位的坐标
glMatrixMode（GL_投影）；
glLoadIdentity（）；
格洛托（0，XWidth，0，YHeight，-1，1）；
//设置线条颜色
GL3F（1.0,0.0,0.0）；
//随机数生成
对于（int i=0；iDoes
rand（）
连续8或12次为您提供相同的4个值集？是的，我得到了4个值集，但正如您所看到的，我也使用这些值绘制线，线是有限的（4或更少）。如果我必须生成10000多行，该怎么办？数组将需要大量内存。@VarunMalhotra此内存约束实际上不是最初的问题，但这是一个好问题。我将提供一个替代方案。
#include "GL/glut.h"
#include "GL/gl.h"
#include <iostream>
#include <stdlib.h>

using namespace std;

#define XWidth 700  // Clipping window size 700*700
#define YHeight 700 

int r[4][4];

void renderFunction() {

  /*Clear Information from last draw
    Sets the current clearing color for use in clearing
    color buffers in RGBA mode.
   */
  glClearColor(0.0, 0.0, 0.0, 0.0);
  glClear(GL_COLOR_BUFFER_BIT);

  //Set line width
  glLineWidth(1);

  //(x,y) coordinates as in pixels
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(0, XWidth, 0, YHeight, -1, 1);

  //Set line color
  glColor3f(1.0, 0.0, 0.0);

  //random num generated
  for(int i=0;i<4;i++){
    //Begin LINE coordinates
    glBegin(GL_LINES);
    glVertex2d(r[i][0], r[i][1]);
    glVertex2d(r[i][2], r[i][3]);
    //End LINE coordinate
    glEnd();
  }

  //Forces previously issued OpenGL commands to begin execution
  glFlush();
}

// Driver program to test above functions
int main(int argc, char** argv) {

  //Initialize GLUT
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_SINGLE);

  //Set Output Window Size
  glutInitWindowSize(XWidth,YHeight);

  //Set the position of Output window corresponding to Screen
  glutInitWindowPosition(100,100);

  //Create the Window
  glutCreateWindow("OpenGL - Classify line among three classes");

  //Set handler functions for drawing
  glutDisplayFunc(renderFunction);

  //random num generated
  for(int i=0;i<4;i++) {
    r[i][0] = rand() % 1000;
    r[i][1] = rand() % 1000;
    r[i][2] = rand() % 1000;
    r[i][3] = rand() % 1000;

    cout<<r[i][0] << " " << r[i][1]<<" "<<r[i][2]<<" "<<r[i][3]<<" i is "<<i<<endl;
  }

  //Start the main loop
  glutMainLoop();
  return 0;
}

#include "GL/glut.h"
#include "GL/gl.h"
#include <iostream>
#include <stdlib.h>

using namespace std;

#define XWidth 700  // Clipping window size 700*700
#define YHeight 700

bool printed;
int random_seed;

void renderFunction() {

  /*Clear Information from last draw
    Sets the current clearing color for use in clearing
    color buffers in RGBA mode.
   */
  glClearColor(0.0, 0.0, 0.0, 0.0);
  glClear(GL_COLOR_BUFFER_BIT);

  //Set line width
  glLineWidth(1);

  //(x,y) coordinates as in pixels
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(0, XWidth, 0, YHeight, -1, 1);


  //Set line color
  glColor3f(1.0, 0.0, 0.0);


  // =============================================
  // set the seed of your random number generator
  // ---------------------------------------------
  srand(random_seed);
  // =============================================

  //random num generated
  for(int i=0;i<4;i++) {
    int r1 = rand() % 1000;
    int r2 = rand() % 1000;
    int r3 = rand() % 1000;
    int r4 = rand() % 1000;

    //Begin LINE coordinates
    glBegin(GL_LINES);
    glVertex2d(r1, r2);
    glVertex2d(r3,r4);
    //End LINE coordinate
    glEnd();

    // ***********************************************
    // make sure the values are only printed the first
    // time around
    // ***********************************************
    if (!printed) {
      cout<<r1<<" "<<r2<<" "<<r3<<" "<<r4<<" i is "<<i<<endl;
    }
  }

  printed = true;

  //Forces previously issued OpenGL commands to begin execution
  glFlush();
}

// Driver program to test above functions
int main(int argc, char** argv) {

  //Initialize GLUT
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_SINGLE);

  //Set Output Window Size
  glutInitWindowSize(XWidth,YHeight);

  //Set the position of Output window corresponding to Screen
  glutInitWindowPosition(100,100);

  //Create the Window
  glutCreateWindow("OpenGL - Classify line among three classes");

  //Set handler functions for drawing
  glutDisplayFunc(renderFunction);


  // =======================================
  // generate a random seed for the lines
  // ---------------------------------------
  srand(time(0));
  random_seed = rand();
  // =======================================

  // ==========================================
  // initialize the printing guard to "false",
  // i.e. "did not print the random values yet"
  // ------------------------------------------
  printed = false;
  // ==========================================


  //Start the main loop
  glutMainLoop();
  return 0;
}