COMPUTER GRAPHICS 1. Drawing the checkerboard. Write the routine checkerboard(in

Question

COMPUTER GRAPHICS

1. Drawing the checkerboard.

Write the routine checkerboard(int size) that draws the checkerboard shown in Figure 2.31b. Place the checkerboard with its lower left corner at (0,0). Each of the 64 squares has length size pixels. Choose two nice colors for the squares. Solution: The ij-th square has lower left corner at (i*size, j*size) for i = 0,..,7 and j = 0..7. The color can be made to alternate between (r1, g1, b1) and (r2, g2, b2) using

if((i + j)%2 ==0) // if i + j is even glColor3f( r1, g1, b1);

Make the checkerboard use two random colors every time you run your checker.exe

2. Write a program that animates whirling hexagons

Requirement: The animation is generated by continuous zoom-in and zoom-out. Starting from the initial configuration of the hexagons, keep zooming in until you reach the smallest hexagon at the center covering the entire screen window, then reverse gear and start zooming out. Once you come back to the initial configuration, start zooming in again. This process is infinitely repeated until the user presses ‘q’ key to exit program. Make sure to slow down the speed of animation so the zooming process can be comfortably viewed. Also, make sure there is no flickering artifact during animation. You may use glutIdleFunc to run the animation as a background process, letting the user interrupt with key input. Also, you may put glutPostRedisplay within the idle function to redisplay the content on the screen after making any change.

Explanation / Answer

working c code

#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>

/*   Create checkerboard texture   */
#define   checkImageWidth 64
#define   checkImageHeight 64
static GLubyte checkImage[checkImageHeight][checkImageWidth][4];

static GLuint texName;

void makeCheckImage(void)
{
   int i, j, c;
  
   for (i = 0; i < checkImageHeight; i++) {
      for (j = 0; j < checkImageWidth; j++) {
         c = (((i&0x8)==0)^((j&0x8)==0))*255;
         checkImage[i][j][0] = (GLubyte) c;
         checkImage[i][j][1] = (GLubyte) c;
         checkImage[i][j][2] = (GLubyte) c;
         checkImage[i][j][3] = (GLubyte) 255;
      }
   }
}

void init(void)
{  
   glClearColor (0.0, 0.0, 0.0, 0.0);
   glShadeModel(GL_FLAT);
   glEnable(GL_DEPTH_TEST);

   makeCheckImage();
   glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

   glGenTextures(1, &texName);
   glBindTexture(GL_TEXTURE_2D, texName);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
   glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,
                checkImageWidth, checkImageHeight,
                0, GL_RGBA, GL_UNSIGNED_BYTE, checkImage);
}

void display(void)
{
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   glEnable(GL_TEXTURE_2D);
   glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
   glBindTexture(GL_TEXTURE_2D, texName);

   glBegin(GL_QUADS);
   glTexCoord2f(0.0, 0.0); glVertex3f(-2.0, -1.0, 0.0);
   glTexCoord2f(0.0, 1.0); glVertex3f(-2.0, 1.0, 0.0);
   glTexCoord2f(1.0, 1.0); glVertex3f(0.0, 1.0, 0.0);
   glTexCoord2f(1.0, 0.0); glVertex3f(0.0, -1.0, 0.0);

   glTexCoord2f(0.0, 0.0); glVertex3f(1.0, -1.0, 0.0);
   glTexCoord2f(0.0, 1.0); glVertex3f(1.0, 1.0, 0.0);
   glTexCoord2f(1.0, 1.0); glVertex3f(2.41421, 1.0, -1.41421);
   glTexCoord2f(1.0, 0.0); glVertex3f(2.41421, -1.0, -1.41421);
   glEnd();
   glFlush();
   glDisable(GL_TEXTURE_2D);
}

void reshape(int w, int h)
{
   glViewport(0, 0, (GLsizei) w, (GLsizei) h);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   gluPerspective(60.0, (GLfloat) w/(GLfloat) h, 1.0, 30.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
   glTranslatef(0.0, 0.0, -3.6);
}

void keyboard (unsigned char key, int x, int y)
{
   switch (key) {
      case 27:
         exit(0);
         break;
      default:
         break;
   }
}

int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
   glutInitWindowSize(250, 250);
   glutInitWindowPosition(100, 100);
   glutCreateWindow(argv[0]);
   init();
   glutDisplayFunc(display);
   glutReshapeFunc(reshape);
   glutKeyboardFunc(keyboard);
   glutMainLoop();
   return 0;
}

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