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

Description:

Perspective in the graphic arts is an approximate representation, on a flat surface, of an image as it is seen by the eye. The two most characteristic features of perspective are that objects are smaller as their distance from the observer increases and the objects appear larger as the viewer is very close to the object. The main objective of this program is to implement the concept of perspective viewing with the help of cube.

Program:

#include<stdio.h>

#include<stdlib.h>

#include<GL/glut.h>

GLfloat v[8][3]={{-100,-100,100},{100,-100,100},{100,100,100},{-100,100,100},{-100,-100,-100}, {100,-100,-100},{100,100,-100},{-100,100,-100}};

GLfloat viewer[3]={ 0.0,0.0,500};

void drawcube(GLfloat *,GLfloat *,GLfloat *,GLfloat *);

void keys(unsigned char k,int x,int y)

{

            if(k=='x') viewer[0]-=10.0;

            if(k=='X')  viewer[0]+=10.0;

            if(k=='y') viewer[1]+=10.0;

            if(k=='Y') viewer[1]-=10.0;

            if(k=='z') viewer[2]+=10.0;

            if(k=='Z') viewer[2]-=10.0;

            glutPostRedisplay();

}

void display()

{

            glClearColor(0.0,0.0,0.0,0.0);

            glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

            glMatrixMode(GL_PROJECTION);

            glLoadIdentity();

            glFrustum(-200,200,-200,200,200,800);

            glMatrixMode(GL_MODELVIEW);

            glLoadIdentity();

            gluLookAt(viewer[0],viewer[1],viewer[2],0,0,0,1,0,0);        

            glColor3f(1.0,0.6,0.3);

            drawcube(v[0],v[1],v[2],v[3]);

            glColor3f(1.0,0.7,0.3);

            drawcube(v[1],v[5],v[6],v[2]);

            glColor3f(1.0,0.0,0.0);

            drawcube(v[3],v[2],v[6],v[7]);

            glColor3f(0.0,1.0,0.0);

            drawcube(v[4],v[5],v[1],v[0]);

            glColor3f(0.0,0.0,1.0);

            drawcube(v[7],v[6],v[5],v[4]);

            glColor3f(1.0,1.0,0.3);

            drawcube(v[3],v[7],v[4],v[0]);

            glFlush();

}

void drawcube(GLfloat *a,GLfloat *b,GLfloat *c,GLfloat *d)

{

            glBegin(GL_POLYGON);

                        //glColor3f(1.0,0.2,0.5);

                        glVertex3fv(a);

                        //glColor3f(0.9,0.1,0.8);

                        glVertex3fv(b);

                        //glColor3f(1.0,1.0,1.0);

                        glVertex3fv(c);

                        //glColor3f(0.7,0.8,0.6);

                        glVertex3fv(d);

            glEnd();

}

void main(int argc, char *argv[])

{

            glutInit(&argc,argv);

            glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB|GLUT_DEPTH);

            glutInitWindowPosition(10,10);

            glutInitWindowSize(500,500);

            glutCreateWindow("Perspective View");

            glutDisplayFunc(display);

            glEnable(GL_DEPTH_TEST);

            glutKeyboardFunc(keys);  // Enable the keyboard function

            glutMainLoop();

}