To draw a color cube and allow the user to move the camera

8.  Program to draw a color cube and allow the user to move the camera suitably to experiment with  perspective viewing using OpenGL functions.

 

#include<stdlib.h>
#include<GL/glut.h>
GLfloat vertices[][3] = {{-1.0,-1.0,-1.0},{1.0,-1.0,-1.0},{1.0,1.0,-1.0},{-1.0,1.0,-1.0},{-1.0,-1.0,1.0},{1.0,-1.0,1.0},{1.0,1.0,1.0},{-1.0,1.0,1.0}};
GLfloat normals[][3] = {{-1.0,-1.0,-1.0},{1.0,-1.0,-1.0},{1.0,1.0,-1.0},{-1.0,1.0,-1.0},{-1.0,-1.0,1.0},{1.0,-1.0,1.0},{1.0,1.0,1.0},{-1.0,1.0,1.0}};
GLfloat colors[][3] = {{0.0,0.0,0.0},{1.0,0.0,0.0},{1.0,1.0,0.0},{1.0,1.0,0.0},
{0.0,0.0,1.0},{1.0,0.0,1.0},{1.0,1.0,1.0},{0.0,1.0,1.0}};
void polygon(int a, int b, int c, int d)
{
            glBegin(GL_POLYGON);
            glColor3fv(colors[a]);
            glNormal3fv(normals[a]);
            glVertex3fv(vertices[a]);
            glColor3fv(colors[b]);
            glNormal3fv(normals[b]);
            glVertex3fv(vertices[b]);
            glColor3fv(colors[c]);
            glNormal3fv(normals[c]);
            glVertex3fv(vertices[c]);
            glColor3fv(colors[d]);
            glNormal3fv(normals[d]);
            glVertex3fv(vertices[d]);
            glEnd();
}
void colorcube()
{           polygon(0,3,2,1);
            polygon(2,3,7,6);
            polygon(0,4,7,3);
            polygon(1,2,6,5);
            polygon(4,5,6,7);
            polygon(0,1,5,4);
}
static GLfloat theta[] = {0.0,0.0,0.0};
static GLint axis =2;
static GLdouble viewer[] = {0.0,0.0,5.0};
void display(void)
{
            glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
            //update viewer position in modelview matrix
  glLoadIdentity();
  gluLookAt(viewer[0],viewer[1],viewer[2],0.0,0.0,0.0,0.0,1.0,0.0);
  //rotate cube
  glRotatef(theta[0],1.0,0.0,0.0);
  glRotatef(theta[1],0.0,1.0,0.0);
  glRotatef(theta[2],0.0,0.0,1.0);
   colorcube();
   glFlush();
   glutSwapBuffers();
}
void mouse(int btn, int state, int x,int y)
{
   if(btn==GLUT_LEFT_BUTTON && state == GLUT_DOWN)              axis=0;
   if(btn==GLUT_MIDDLE_BUTTON && state == GLUT_DOWN)        axis=1;
   if(btn==GLUT_RIGHT_BUTTON && state == GLUT_DOWN)           axis=2;
   theta[axis] += 2.0;
   if(theta[axis]>360.0)theta[axis]-=360.0;
   display();
}
void Keys(unsigned char key, int x,int y)
{
            // use x, X,y,Y,z and Z keys to move viewer
            if(key =='x') viewer[0]-=1.0;
            if(key =='X') viewer[0]+=1.0;
            if(key =='y') viewer[1]-=1.0;
            if(key =='Y') viewer[1]+=1.0;
            if(key =='z') viewer[2]-=1.0;
            if(key =='Z') viewer[2]+=1.0;
      glutPostRedisplay();
}
void myReshape(int w,int h)
{
            glViewport(0,0,w,h);
            //use the prespective view
            glMatrixMode(GL_PROJECTION);
            glLoadIdentity();
           if(w<=h)
glFrustum(-2.0,2.0,-2.0*(GLfloat) h/(GLfloat) w, 2.0*(GLfloat) h/(GLfloat) w ,2.0,20.0);
    else
glFrustum(-2.0,2.0,-2.0*(GLfloat) w/(GLfloat) h, 2.0*(GLfloat) w/(GLfloat) h ,2.0,20.0);
  glMatrixMode(GL_MODELVIEW);
}
Int main(int argc,char** argv)
{
            glutInit(&argc,argv);
            glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB|GLUT_DEPTH);
             glutInitWindowSize(500,500);
            glutCreateWindow("colorcube viewer");
            glutReshapeFunc(myReshape);
            glutDisplayFunc(display);
            glutMouseFunc(mouse);
            glutKeyboardFunc(Keys);
            glEnable(GL_DEPTH_TEST);
            glutMainLoop();
            return 0;
}