/* C checkerboard */
#define GLUT_DISABLE_ATEXIT_HACK

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

#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) 0;
         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, checkImage
+Height, 
                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);

   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
   glTranslatef(0.0, 0.0, -2.0);

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

   glFlush();
   glDisable(GL_TEXTURE_2D);
}

void reshape(int w, int h)
{
   glViewport(0, 0, (GLsizei) w, (GLsizei) h);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   gluPerspective(112.5, (GLfloat) w/(GLfloat) h, 0.1, 30.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
   glTranslatef(0.0, 0.0, -2.0);
}

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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#!/usr/bin/perl

use OpenGL ':all';
use strict;
use warnings;

my $checker;

main();


sub init {
  glClearColor(0,0,0,0);
  glShadeModel(GL_FLAT);
  glEnable(GL_DEPTH_TEST);

  my $bm;
  glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
  glGenTextures_s(1, $checker);
  $checker = unpack "I", $checker;
  for my $i (0 .. 63) {
    for my $j (0 .. 63) {
      my $c = ((($i & 8) == 0) ^ (($j & 8) != 0)) * 255;
      $bm .= pack "C4", $c, $c, 0, 255;
    }
  }

  glBindTexture(GL_TEXTURE_2D, $checker);

  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_s(
    GL_TEXTURE_2D, 0, GL_RGBA,
    64, 64,
    0, GL_RGBA, GL_UNSIGNED_BYTE, $bm,
  );
}


sub display {
  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, $checker);

  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glTranslatef(0.0, 0.0, -2.0);

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

  glFlush();
  glDisable(GL_TEXTURE_2D);
  glutSwapBuffers();
}


sub reshape {
  my ($w, $h) = @_;
  glViewport(0, 0, $w, $h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(112.5, $w/$h, 0.01, 30.0);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glTranslatef(0.0, 0.0, -3.0);
}


sub keyboard {
  my ($key, $x, $y) = @_;
  if ($key == 27) { exit }
}


sub main {
  glutInit();
  glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
  glutInitWindowSize(250, 250);
  glutInitWindowPosition(100, 100);
  glutCreateWindow($0);
  init();
  glutDisplayFunc(\&display);
  glutReshapeFunc(\&reshape);
  glutKeyboardFunc(\&keyboard);
  glutMainLoop();
  return 0; 
}
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