当我在OpenGL中按下一个键时无法绘制形状

Posted 2023-02-22

【中文标题】当我在OpenGL中按下一个键时无法绘制形状

【英文标题】：Can't draw shape when I press a key in OpenGL

【发布时间】：2019-10-07 11:02:56

【问题描述】：

我在绘制一些形状时遇到了问题。当我执行程序时，我应该只看到坐标，然后按下一个键来绘制形状，但默认情况下它已经绘制了立方体，然后是金字塔。当我按“p”键时如何绘制金字塔，当我按“c”时如何绘制立方体？我尝试了一些东西，但它似乎不起作用:(

#include <stdlib.h>
#include <math.h>
#include "dependente\freeglut\freeglut.h"
#include "dependente\glfw\glfw3.h"
#include <stdio.h>
#define  RADDEG  57.29577951f

float XUP[3] =  1,0,0 , XUN[3] =  -1, 0, 0 ,
YUP[3] =  0,1,0 , YUN[3] =  0,-1, 0 ,
ZUP[3] =  0,0,1 , ZUN[3] =  0, 0,-1 ,
ORG[3] =  0,0,0 ;

GLfloat viewangle = 0, tippangle = 0, traj[120][3];

GLfloat d[3] =  0.1, 0.1, 0.1 ;

GLfloat  xAngle = 0.0, yAngle = 0.0, zAngle = 0.0;

//  Use arrow keys to rotate entire scene !!!

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

    switch (key) 

    case GLUT_KEY_LEFT:  viewangle -= 5;  break;
    case GLUT_KEY_RIGHT:  viewangle += 5;  break;
    case GLUT_KEY_UP:  tippangle -= 5;  break;
    case GLUT_KEY_DOWN:  tippangle += 5;  break;

    default: printf("Special key %c == %d", key, key);
    

    glutPostRedisplay();

void Pyramid(void) //draw the pyramid shape

    glBegin(GL_TRIANGLE_FAN);
    glColor3f(1.0f, 0.0f, 0.0f); glVertex3f(0.0f, 1.0f, 0.0f);   //V0(red)
    glColor3f(0.0f, 1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f);   //V1(green)
    glColor3f(0.0f, 0.0f, 1.0f); glVertex3f(1.0f, -1.0f, 1.0f);   //V2(blue)
    glColor3f(0.0f, 1.0f, 0.0f); glVertex3f(1.0f, -1.0f, -1.0f);   //V3(green)
    glColor3f(0.0f, 0.0f, 1.0f); glVertex3f(-1.0f, -1.0f, -1.0f);   //V4(blue)
    glColor3f(0.0f, 1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f);   //V1(green)
    glEnd();


void Draw_Box(void)

    glBegin(GL_QUADS);

    glColor3f(0.0, 0.7, 0.1);     // Front - green
    glVertex3f(-1.0, 1.0, 1.0);
    glVertex3f(1.0, 1.0, 1.0);
    glVertex3f(1.0, -1.0, 1.0);
    glVertex3f(-1.0, -1.0, 1.0);

    glColor3f(0.9, 1.0, 0.0);    // Back  - yellow
    glVertex3f(-1.0, 1.0, -1.0);
    glVertex3f(1.0, 1.0, -1.0);
    glVertex3f(1.0, -1.0, -1.0);
    glVertex3f(-1.0, -1.0, -1.0);

    glColor3f(0.2, 0.2, 1.0);     // Top - blue 
    glVertex3f(-1.0, 1.0, 1.0);
    glVertex3f(1.0, 1.0, 1.0);
    glVertex3f(1.0, 1.0, -1.0);
    glVertex3f(-1.0, 1.0, -1.0);

    glColor3f(0.7, 0.0, 0.1);    // Bottom - red
    glVertex3f(-1.0, -1.0, 1.0);
    glVertex3f(1.0, -1.0, 1.0);
    glVertex3f(1.0, -1.0, -1.0);
    glVertex3f(-1.0, -1.0, -1.0);

    glEnd();


void Keyboard(unsigned char key, int x, int y) //press a key to perform actions

    switch (key) 

    case 'd': d[0] += 0.1;  break;
    case 'a': d[0] -= 0.1;  break;
    case 'w': d[1] += 0.1;  break;
    case 's': d[1] -= 0.1;  break;
    case 'm': d[2] += 0.1;  break;
    case 'n': d[2] -= 0.1;  break;
    case 'p': Pyramid();  break;
    case 'c': Draw_Box();  break;

    case 'x': xAngle += 5;  break;
    case 'y': yAngle += 5;  break;
    case 'z': zAngle += 5;  break;

    default: printf("   Keyboard %c == %d", key, key);
    

    glutPostRedisplay();




void Triad(void)

    glColor3f(1.0, 1.0, 1.0); //set the dark grey color 

    glBegin(GL_LINES);
    glVertex3fv(ORG); glVertex3fv(XUP);
    glVertex3fv(ORG); glVertex3fv(YUP);
    glVertex3fv(ORG); glVertex3fv(ZUP);
    glEnd();

    glRasterPos3f(1.1, 0.0, 0.0);
    glutBitmapCharacter(GLUT_BITMAP_HELVETICA_18, 'X'); //draw the x axis

    glRasterPos3f(0.0, 1.1, 0.0);
    glutBitmapCharacter(GLUT_BITMAP_HELVETICA_18, 'Y'); //draw the y axis

    glRasterPos3f(0.0, 0.0, 1.1);
    glutBitmapCharacter(GLUT_BITMAP_HELVETICA_18, 'Z'); //draw the z axis 







void redraw(void)

    int v;

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glEnable(GL_DEPTH_TEST);

    glLoadIdentity();

    glTranslatef(0, 0, -3);
    glRotatef(tippangle, 1, 0, 0);  // Up and down arrow keys 'tip' view.
    glRotatef(viewangle, 0, 1, 0);  // Right/left arrow keys 'turn' view.

    glDisable(GL_LIGHTING);

    Triad();


    glPushMatrix();
    glTranslatef(d[0], d[1], d[2]);    // Move box down X axis.
    glScalef(0.2, 0.2, 0.2);
    glRotatef(zAngle, 0, 0, 1);
    glRotatef(yAngle, 0, 1, 0);
    glRotatef(xAngle, 1, 0, 0);
    //Draw_Box(); // if i delete comment the cube it's drawn
    //Pyramid(); // if i delete this the pyramid it's drawn inside the cube
    glPopMatrix();

    glutSwapBuffers();


//---+----3----+----2----+----1----+---<>---+----1----+----2----+----3----+----4

int main(int argc, char** argv)

    glutInit(&argc, argv);
    glutInitWindowSize(900, 600);
    glutInitWindowPosition(300, 300);
    glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE);

    glutCreateWindow("Big HW1");
    glutDisplayFunc(redraw);
    glutKeyboardFunc(Keyboard);
    glutSpecialFunc(Special_Keys);

    glClearColor(0.1, 0.0, 0.1, 1.0);

    glMatrixMode(GL_PROJECTION);
    gluPerspective(60, 1.5, 1, 10);
    glMatrixMode(GL_MODELVIEW);
    glutMainLoop();

    return 1;

【问题讨论】：

您的 redraw 函数会清除屏幕，因此不要在键盘处理程序中绘制立方体和金字塔，而是设置一个类似 drawPyramid 或 drawCube 的标志并在您的 redraw 中检查它功能。

【参考方案1】：

有几种方法可以解决这个问题。一种是创建一个全局变量，它会告诉您是否要绘制形状：

bool draw_pyramid = false;
bool draw_box = false;

然后，在您的键盘句柄函数中，执行以下操作：

case 'p': draw_pyramid = true;  break;
case 'c': draw_box = true;  break;

最后，在您的重绘函数中，进行条件绘制：

if ( draw_pyramid )
    Pyramid();

if ( draw_box )
    Draw_Box();

【讨论】：

谢谢，它工作了

通过取消设置其他标志，或使用单个变量来确定要绘制的内容。

你可以试试，例如：case 'p': draw_pyramid = true; draw_box = false; break;

是的，成功了，非常感谢，今天的灵感对我来说非常低，这似乎是一件容易的事情......