我创建了一个地面，但我在 openGL 中看不到地面。我该如何解决？

Posted 2023-02-22

【中文标题】我创建了一个地面，但我在 openGL 中看不到地面。我该如何解决？

【英文标题】：I created a ground, but I can't see the ground in openGL. How can I fix it?

【发布时间】：2015-12-10 08:34:06

【问题描述】：

此代码正常运行，但运行程序后屏幕上看不到我创建的地面。我想在屏幕上看到整个地面。

如何修复代码？

#define A glVertex3f (0.5,  1.2, 0)
#define B glVertex3f (1, 2, 0)
#define C glVertex3f (2, 1.4, 0)
#define D glVertex3f ( 0.5,  0.5, -0.5)
#define E glVertex3f (-0.5,  0.5,  0.5)
#define F glVertex3f (-0.5, -0.5,  0.5)
#define G glVertex3f ( 0.5, -0.5,  0.5)
#define H glVertex3f ( 0.5,  0.5,  0.5)
#define _USE_MATH_DEFINES
#include <cmath>
#include <stdlib.h>
#include <math.h>
#include <glut.h>
float distance = 5.0;
int longitude = 0, latitude = 0, ainc = 5;
int lastx = -1, lasty = -1;
int x=0,z=0;
int y;
int data[17][21]=
14 ,25, 45 ,55 ,68 ,70 ,84 ,91 ,97, 101 ,105 ,105 ,105, 105 ,110 ,110,   110, 110 ,110, 110, 110,
5, 18, 43, 62 ,73, 82, 88, 94, 99, 102 ,105, 105 ,105, 105, 110, 110 ,110 ,110 ,110, 110, 110,
5, 18 ,38 ,56, 69, 77, 86, 94, 99, 103, 106, 105, 105, 105, 110, 110, 110, 110, 110, 110, 110,
5 ,9 ,31, 48, 60, 71, 81, 87, 95, 101, 106, 105, 105, 105, 110, 110, 110, 110, 110, 110, 110,
5, 5, 18, 37, 49, 56, 62, 81, 91, 94, 101, 105, 105, 105, 110, 110, 110 ,110 ,110, 110, 110,
5, 5, 12, 23 ,34, 40, 53 ,66 ,77 ,82, 97, 103, 105, 105, 109, 110, 110, 110, 110, 115, 115,
4 ,5 ,8 ,15, 20, 24, 35, 39, 40, 77, 92, 101, 104, 104 ,105, 110, 110, 110, 115, 115, 115,
5, 7 ,22, 36, 46, 48, 48, 44 ,50, 58, 80, 96, 96, 97, 106, 110, 110, 115, 115, 115, 115,
4, 15 ,31 ,46 ,61, 68, 69, 63, 53, 50, 67, 82, 84, 103, 108, 110, 110, 115, 115, 115, 115,
4, 12, 31, 46, 64, 78, 82, 80, 69, 54, 73, 71, 92, 105, 108, 110, 110, 115, 115, 115, 115,
6, 26 ,35 ,45, 63, 75, 84, 87, 84, 74 ,77, 80, 96, 103, 108, 110, 110, 110, 115, 115, 115,
21, 30, 46, 57 ,64 ,76 ,85 ,92 ,92, 87 ,79 ,80 ,86 ,102, 106, 110, 105 ,110, 115, 115, 115,
27, 40, 48 ,62 ,75 ,84 ,92, 96, 97 ,94 ,88 ,80 ,80 ,91, 104, 105, 105, 105, 110, 115, 115,
33, 43, 55, 65, 75, 87, 96, 101, 101, 101, 97, 92, 80, 80, 98, 105, 105, 105, 105, 110, 115,
45, 50, 58, 68, 80, 91, 99, 102, 105, 105, 105, 99, 90, 80, 80, 97, 105, 105, 105, 110, 100,
50, 60, 65, 71, 84, 95, 101, 105, 105, 107, 107, 106, 102, 101, 92, 80, 98, 104, 105, 100, 100,
60, 70, 76, 83, 88 ,96, 103, 106 ,107, 108 ,110, 109 ,108 ,108, 106, 101 ,90, 100, 100, 100, 100;
void display (void)

float xc, yc, zc;
int type = GL_TRIANGLE_STRIP;   // or GL_LINE_LOOP
xc = distance * cos (latitude /180.0*M_PI) * cos (longitude/180.0*M_PI);
yc = distance * sin (latitude /180.0*M_PI);
zc = distance * cos (latitude /180.0*M_PI) * sin (longitude/180.0*M_PI);
glLoadIdentity ();
gluLookAt (xc, yc, zc,  0.0, 0.0, 0.0,  0.0, 1.0, 0.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);  
glColor3f (1.0, 1.0, 1.0);
glBegin (type);  
    for (int i = 0; i < 17; i++)


    z=z+20;
    for (int k = 0; k < 21; k=k+1)
    
        y=data[i][k];
        if(y>0&&y<50)
            glColor3f(0.0, 1.0, 0.0);
        if(y>=50&&y<80)
            glColor3f(1.0, 1.0, 0.0);
        if(y>=80)
            glColor3f(1.0, 0.0, 0.0);


        glVertex3f(x, data[i][k], z);
        x=x+20;

        

    


  glEnd();  // front



  glutSwapBuffers ();
  

 void keyboard (unsigned char key, int x, int y)
 
 switch (key) 
 case 27: case 'q': case 'Q':
exit (EXIT_SUCCESS);
break;
 
 

void special (int key, int x, int y)

switch (key) 
case GLUT_KEY_UP:
distance *= 2;
break;
case GLUT_KEY_DOWN:
distance /= 2;
break;

glutPostRedisplay ();


void click (int button, int state, int x, int y)

if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) 
lastx = x;
lasty = y;



void mouse (int x, int y)

if (x > lastx) 
longitude = (longitude + ainc) % 360;
 else if (x < lastx) 
longitude = (longitude - ainc) % 360;

if (y > lasty) 
latitude = (latitude + ainc) % 360;
  else if (y < lasty) 
latitude = (latitude - ainc) % 360;
 
 lastx = x;
 lasty = y;
 glutPostRedisplay ();
 

 void reshape (int w, int h)

glViewport (0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode (GL_PROJECTION);
glLoadIdentity ();
gluPerspective (65.0, (GLfloat) w / (GLfloat) h, 1.0, 20.0);
glMatrixMode (GL_MODELVIEW);
glLoadIdentity ();
glTranslatef (0.0, 0.0, -5.0);



 int main (int argc, char *argv[])
 
 glutInit (&argc, argv);
   glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
 glutCreateWindow (argv[0]);
 glMatrixMode (GL_PROJECTION);
 glLoadIdentity ();
 gluPerspective(50.0, 1.0, 3.0, 7.0);
 glMatrixMode (GL_MODELVIEW);
 glutDisplayFunc (display);
 glutKeyboardFunc (keyboard);
 glutSpecialFunc (special);
 glutMouseFunc (click);
 glutMotionFunc (mouse);
 glutReshapeFunc (reshape);
  glEnable (GL_DEPTH_TEST);
  glutMainLoop ();
 return EXIT_SUCCESS;
 

【参考方案1】：

我可以看到一些你可以检查的东西 1) 在 reshape Fucntion glTranslatef (0.0, 0.0, -5.0) 被调用，之后在显示函数中调用 loadIdentity() 将重置矩阵。所以翻译可能不适用于您正在绘制的对象。 2) 也尝试将 Z 值更向内更改 Z 轴。 3) 更改您的投影远点和 FOV 角度，因为您的 X 值非常高。 我注意到您的 x、y、z 是全局值并且不会在重塑时重置的另一件事。 希望对您有所帮助。