#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>
#ifdef GL_VERSION_1_1
#define checkImageWidth 64
#define checkImageHeight 64
#define subImageWidth 16
#define subImageHeight 16
static GLubyte checkImage[checkImageHeight][checkImageWidth][4];
static GLubyte subImage[subImageHeight][subImageWidth][4];
static GLuint texName;
void makeCheckImages(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;
}
}
for (i = 0; i < subImageHeight; i++) {
for (j = 0; j < subImageWidth; j++) {
c = ((((i&0x4)==0)^((j&0x4)==0)))*255;
subImage[i][j][0] = (GLubyte) c;
subImage[i][j][1] = (GLubyte) 0;
subImage[i][j][2] = (GLubyte) 0;
subImage[i][j][3] = (GLubyte) 255;
}
}
}
void init(void)
{
glClearColor (0.0, 0.0, 0.0, 0.0);
glShadeModel(GL_FLAT);
glEnable(GL_DEPTH_TEST);
makeCheckImages();
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 's':
case 'S':
glBindTexture(GL_TEXTURE_2D, texName);
glTexSubImage2D(GL_TEXTURE_2D, 0, 12, 44, subImageWidth,
subImageHeight, GL_RGBA,
GL_UNSIGNED_BYTE, subImage);
glutPostRedisplay();
break;
case 'r':
case 'R':
glBindTexture(GL_TEXTURE_2D, texName);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, checkImageWidth,
checkImageHeight, 0, GL_RGBA,
GL_UNSIGNED_BYTE, checkImage);
glutPostRedisplay();
break;
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;
}
#else
int main(int argc, char** argv)
{
fprintf (stderr, "This program demonstrates a feature which is not in OpenGL Version 1.0.\n");
fprintf (stderr, "If your implementation of OpenGL Version 1.0 has the right extensions,\n");
fprintf (stderr, "you may be able to modify this program to make it run.\n");
return 0;
}
#endif