Would someone be kind enough to write the same code the “proper” way then.
Here is the entire code:
/*
lightposition.c
Nate Robins, 1997
Tool for teaching about OpenGL light positioning.
*/
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include "glm.h"
typedef struct _cell {
int id;
int x, y;
float min, max;
float value;
float step;
char* info;
char* format;
} cell;
cell lookat[9] = {
{ 1, 180, 120, -5.0, 5.0, 0.0, 0.1,
"Specifies the X position of the eye point.", "%.2f" },
{ 2, 240, 120, -5.0, 5.0, 0.0, 0.1,
"Specifies the Y position of the eye point.", "%.2f" },
{ 3, 300, 120, -5.0, 5.0, 2.0, 0.1,
"Specifies the Z position of the eye point.", "%.2f" },
{ 4, 180, 160, -5.0, 5.0, 0.0, 0.1,
"Specifies the X position of the reference point.", "%.2f" },
{ 5, 240, 160, -5.0, 5.0, 0.0, 0.1,
"Specifies the Y position of the reference point.", "%.2f" },
{ 6, 300, 160, -5.0, 5.0, 0.0, 0.1,
"Specifies the Z position of the reference point.", "%.2f" },
{ 7, 180, 200, -2.0, 2.0, 0.0, 0.1,
"Specifies the X direction of the up vector.", "%.2f" },
{ 8, 240, 200, -2.0, 2.0, 1.0, 0.1,
"Specifies the Y direction of the up vector.", "%.2f" },
{ 9, 300, 200, -2.0, 2.0, 0.0, 0.1,
"Specifies the Z direction of the up vector.", "%.2f" },
};
cell light[4] = {
{ 10, 180, 40, -5.0, 5.0, 1.5, 0.1,
"Specifies X coordinate of light vector.", "%.2f" },
{ 11, 240, 40, -5.0, 5.0, 1.0, 0.1,
"Specifies Y coordinate of light vector.", "%.2f" },
{ 12, 300, 40, -5.0, 5.0, 1.0, 0.1,
"Specifies Z coordinate of light vector.", "%.2f" },
{ 13, 360, 40, 0.0, 1.0, 0.0, 1.0,
"Specifies directional (0) or positional (1) light.", "%.2f" }
};
GLboolean swapped = GL_FALSE;
GLboolean world_draw = GL_TRUE;
GLMmodel* pmodel = NULL;
GLint selection = 0;
void redisplay_all(void);
GLdouble projection[16], modelview[16], inverse[16];
GLuint window, world, screen, command;
GLuint sub_width = 256, sub_height = 256;
GLvoid *font_style = GLUT_BITMAP_TIMES_ROMAN_10;
void
setfont(char* name, int size)
{
font_style = GLUT_BITMAP_HELVETICA_10;
if (strcmp(name, "helvetica") == 0) {
if (size == 12)
font_style = GLUT_BITMAP_HELVETICA_12;
else if (size == 18)
font_style = GLUT_BITMAP_HELVETICA_18;
} else if (strcmp(name, "times roman") == 0) {
font_style = GLUT_BITMAP_TIMES_ROMAN_10;
if (size == 24)
font_style = GLUT_BITMAP_TIMES_ROMAN_24;
} else if (strcmp(name, "8x13") == 0) {
font_style = GLUT_BITMAP_8_BY_13;
} else if (strcmp(name, "9x15") == 0) {
font_style = GLUT_BITMAP_9_BY_15;
}
}
void
drawstr(GLuint x, GLuint y, char* format, ...)
{
va_list args;
char buffer[255], *s;
va_start(args, format);
vsprintf(buffer, format, args);
va_end(args);
glRasterPos2i(x, y);
for (s = buffer; *s; s++)
glutBitmapCharacter(font_style, *s);
}
void
cell_draw(cell* cell)
{
glColor3ub(0, 255, 128);
if (selection == cell->id) {
glColor3ub(255, 255, 0);
drawstr(10, 240, cell->info);
glColor3ub(255, 0, 0);
}
drawstr(cell->x, cell->y, cell->format, cell->value);
}
int
cell_hit(cell* cell, int x, int y)
{
if (x > cell->x && x < cell->x + 60 &&
y > cell->y-30 && y < cell->y+10)
return cell->id;
return 0;
}
void
cell_update(cell* cell, int update)
{
if (selection != cell->id)
return;
cell->value += update * cell->step;
if (cell->value < cell->min)
cell->value = cell->min;
else if (cell->value > cell->max)
cell->value = cell->max;
}
void
cell_vector(float* dst, cell* cell, int num)
{
while (--num >= 0)
dst[num] = cell[num].value;
}
void
drawmodel(void)
{
/* if (!pmodel) {
pmodel = glmReadOBJ("data/soccerball.obj");
if (!pmodel) exit(0);
glmUnitize(pmodel);
glmFacetNormals(pmodel);
glmVertexNormals(pmodel, 90.0);
}
glmDraw(pmodel, GLM_SMOOTH | GLM_MATERIAL);*/
glutSolidSphere(0.4,16,16);
}
void
drawaxes(void)
{
glColor3ub(255, 0, 0);
glBegin(GL_LINE_STRIP);
glVertex3f(0.0, 0.0, 0.0);
glVertex3f(1.0, 0.0, 0.0);
glVertex3f(0.75, 0.25, 0.0);
glVertex3f(0.75, -0.25, 0.0);
glVertex3f(1.0, 0.0, 0.0);
glVertex3f(0.75, 0.0, 0.25);
glVertex3f(0.75, 0.0, -0.25);
glVertex3f(1.0, 0.0, 0.0);
glEnd();
glBegin(GL_LINE_STRIP);
glVertex3f(0.0, 0.0, 0.0);
glVertex3f(0.0, 1.0, 0.0);
glVertex3f(0.0, 0.75, 0.25);
glVertex3f(0.0, 0.75, -0.25);
glVertex3f(0.0, 1.0, 0.0);
glVertex3f(0.25, 0.75, 0.0);
glVertex3f(-0.25, 0.75, 0.0);
glVertex3f(0.0, 1.0, 0.0);
glEnd();
glBegin(GL_LINE_STRIP);
glVertex3f(0.0, 0.0, 0.0);
glVertex3f(0.0, 0.0, 1.0);
glVertex3f(0.25, 0.0, 0.75);
glVertex3f(-0.25, 0.0, 0.75);
glVertex3f(0.0, 0.0, 1.0);
glVertex3f(0.0, 0.25, 0.75);
glVertex3f(0.0, -0.25, 0.75);
glVertex3f(0.0, 0.0, 1.0);
glEnd();
glColor3ub(255, 255, 0);
glRasterPos3f(1.1, 0.0, 0.0);
glutBitmapCharacter(GLUT_BITMAP_HELVETICA_12, 'x');
glRasterPos3f(0.0, 1.1, 0.0);
glutBitmapCharacter(GLUT_BITMAP_HELVETICA_12, 'y');
glRasterPos3f(0.0, 0.0, 1.1);
glutBitmapCharacter(GLUT_BITMAP_HELVETICA_12, 'z');
}
void
identity(GLdouble m[16])
{
m[0+4*0] = 1; m[0+4*1] = 0; m[0+4*2] = 0; m[0+4*3] = 0;
m[1+4*0] = 0; m[1+4*1] = 1; m[1+4*2] = 0; m[1+4*3] = 0;
m[2+4*0] = 0; m[2+4*1] = 0; m[2+4*2] = 1; m[2+4*3] = 0;
m[3+4*0] = 0; m[3+4*1] = 0; m[3+4*2] = 0; m[3+4*3] = 1;
}
GLboolean
invert(GLdouble src[16], GLdouble inverse[16])
{
double t;
int i, j, k, swap;
GLdouble tmp[4][4];
identity(inverse);
for (i = 0; i < 4; i++) {
for (j = 0; j < 4; j++) {
tmp[i][j] = src[i*4+j];
}
}
for (i = 0; i < 4; i++) {
/* look for largest element in column. */
swap = i;
for (j = i + 1; j < 4; j++) {
if (fabs(tmp[j][i]) > fabs(tmp[i][i])) {
swap = j;
}
}
if (swap != i) {
/* swap rows. */
for (k = 0; k < 4; k++) {
t = tmp[i][k];
tmp[i][k] = tmp[swap][k];
tmp[swap][k] = t;
t = inverse[i*4+k];
inverse[i*4+k] = inverse[swap*4+k];
inverse[swap*4+k] = t;
}
}
if (tmp[i][i] == 0) {
/* no non-zero pivot. the matrix is singular, which
shouldn't happen. This means the user gave us a bad
matrix. */
return GL_FALSE;
}
t = tmp[i][i];
for (k = 0; k < 4; k++) {
tmp[i][k] /= t;
inverse[i*4+k] /= t;
}
for (j = 0; j < 4; j++) {
if (j != i) {
t = tmp[j][i];
for (k = 0; k < 4; k++) {
tmp[j][k] -= tmp[i][k]*t;
inverse[j*4+k] -= inverse[i*4+k]*t;
}
}
}
}
return GL_TRUE;
}
float
normalize(float* v)
{
float length;
length = sqrt(v[0]*v[0] + v[1]*v[1] + v[2]*v[2]);
v[0] /= length;
v[1] /= length;
v[2] /= length;
return length;
}
void
main_reshape(int width, int height)
{
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0, width, height, 0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
#define GAP 25 /* gap between subwindows */
sub_width = (width-GAP*3)/2.0;
sub_height = (height-GAP*3)/2.0;
glutSetWindow(world);
glutPositionWindow(GAP, GAP);
glutReshapeWindow(sub_width, sub_height);
glutSetWindow(screen);
glutPositionWindow(GAP+sub_width+GAP, GAP);
glutReshapeWindow(sub_width, sub_height);
glutSetWindow(command);
glutPositionWindow(GAP, GAP+sub_height+GAP);
glutReshapeWindow(sub_width+GAP+sub_width, sub_height);
}
void
main_display(void)
{
glClearColor(0.8, 0.8, 0.8, 0.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glColor3ub(0, 0, 0);
setfont("helvetica", 12);
drawstr(GAP, GAP-5, "World-space view");
drawstr(GAP+sub_width+GAP, GAP-5, "Screen-space view");
drawstr(GAP, GAP+sub_height+GAP-5, "Command manipulation window");
glutSwapBuffers();
}
void
main_keyboard(unsigned char key, int x, int y)
{
switch (key) {
case 's':
swapped = !swapped;
break;
case 'r':
light[0].value = 1.5;
light[1].value = 1.0;
light[2].value = 1.0;
light[3].value = 0.0;
lookat[0].value = 0.0;
lookat[1].value = 0.0;
lookat[2].value = 2.0;
lookat[3].value = 0.0;
lookat[4].value = 0.0;
lookat[5].value = 0.0;
lookat[6].value = 0.0;
lookat[7].value = 1.0;
lookat[8].value = 0.0;
break;
case 27:
exit(0);
}
redisplay_all();
}
void
world_reshape(int width, int height)
{
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(60.0, (GLfloat)width/height, 0.01, 256.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.0, 0.0, -5.0);
glRotatef(-45.0, 0.0, 1.0, 0.0);
glClearColor(0.0, 0.0, 0.0, 0.0);
glEnable(GL_DEPTH_TEST);
glEnable(GL_LIGHT0);
}
void
world_display(void)
{
GLfloat pos[4];
double length;
float l[3];
cell_vector(pos, light, 4);
l[0] = lookat[3].value - lookat[0].value;
l[1] = lookat[4].value - lookat[1].value;
l[2] = lookat[5].value - lookat[2].value;
invert(modelview, inverse);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
if (swapped) {
glPushMatrix();
glTranslatef(l[0], l[1], l[2]);
glMultMatrixd(inverse);
glColor3ub(255, 255, 255);
glBegin(GL_LINE_STRIP);
glVertex3f(0.0, 0.0, 0.0);
if (pos[3] == 0) /* 10.0 = 'infinite' light */
glVertex3f(pos[0]*10.0,pos[1]*10.0,pos[2]*10.0);
else
glVertex3f(pos[0], pos[1], pos[2]);
glEnd();
glLightfv(GL_LIGHT0, GL_POSITION, pos);
glPopMatrix();
} else {
glColor3ub(255, 255, 255);
glBegin(GL_LINE_STRIP);
glVertex3f(0.0, 0.0, 0.0);
if (pos[3] == 0) /* 10.0 = 'infinite' light */
glVertex3f(pos[0]*10.0,pos[1]*10.0,pos[2]*10.0);
else
glVertex3f(pos[0], pos[1], pos[2]);
glEnd();
glLightfv(GL_LIGHT0, GL_POSITION, pos);
}
length = normalize(l);
if (world_draw) {
glEnable(GL_LIGHTING);
drawmodel();
glDisable(GL_LIGHTING);
}
glPushMatrix();
glMultMatrixd(inverse);
/* draw the axes and eye vector */
glPushMatrix();
glColor3ub(0, 0, 255);
glBegin(GL_LINE_STRIP);
glVertex3f(0.0, 0.0, 0.0);
glVertex3f(0.0, 0.0, -1.0*length);
glVertex3f(0.1, 0.0, -0.9*length);
glVertex3f(-0.1, 0.0, -0.9*length);
glVertex3f(0.0, 0.0, -1.0*length);
glVertex3f(0.0, 0.1, -0.9*length);
glVertex3f(0.0, -0.1, -0.9*length);
glVertex3f(0.0, 0.0, -1.0*length);
glEnd();
glColor3ub(255, 255, 0);
glRasterPos3f(0.0, 0.0, -1.1*length);
glutBitmapCharacter(GLUT_BITMAP_HELVETICA_12, 'e');
glColor3ub(255, 0, 0);
glScalef(0.4, 0.4, 0.4);
drawaxes();
glPopMatrix();
invert(projection, inverse);
glMultMatrixd(inverse);
/* draw the viewing frustum */
glColor3f(0.2, 0.2, 0.2);
glBegin(GL_QUADS);
glVertex3i(1, 1, 1);
glVertex3i(-1, 1, 1);
glVertex3i(-1, -1, 1);
glVertex3i(1, -1, 1);
glEnd();
glColor3ub(128, 196, 128);
glBegin(GL_LINES);
glVertex3i(1, 1, -1);
glVertex3i(1, 1, 1);
glVertex3i(-1, 1, -1);
glVertex3i(-1, 1, 1);
glVertex3i(-1, -1, -1);
glVertex3i(-1, -1, 1);
glVertex3i(1, -1, -1);
glVertex3i(1, -1, 1);
glEnd();
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glColor4f(0.2, 0.2, 0.4, 0.5);
glBegin(GL_QUADS);
glVertex3i(1, 1, -1);
glVertex3i(-1, 1, -1);
glVertex3i(-1, -1, -1);
glVertex3i(1, -1, -1);
glEnd();
glDisable(GL_BLEND);
glPopMatrix();
glutSwapBuffers();
}
void
world_menu(int value)
{
switch (value) {
case 'm':
world_draw = !world_draw;
break;
}
redisplay_all();
}
void
screen_reshape(int width, int height)
{
GLfloat pos[4];
cell_vector(pos, light, 4);
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(60.0, (float)width/height, 0.5, 8.0);
glGetDoublev(GL_PROJECTION_MATRIX, projection);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
if (swapped) {
glLightfv(GL_LIGHT0, GL_POSITION, pos);
gluLookAt(lookat[0].value, lookat[1].value, lookat[2].value,
lookat[3].value, lookat[4].value, lookat[5].value,
lookat[6].value, lookat[7].value, lookat[8].value);
} else {
gluLookAt(lookat[0].value, lookat[1].value, lookat[2].value,
lookat[3].value, lookat[4].value, lookat[5].value,
lookat[6].value, lookat[7].value, lookat[8].value);
glLightfv(GL_LIGHT0, GL_POSITION, pos);
}
glGetDoublev(GL_MODELVIEW_MATRIX, modelview);
glClearColor(0.2, 0.2, 0.2, 0.0);
glEnable(GL_DEPTH_TEST);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
}
void
screen_display(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
drawmodel();
glutSwapBuffers();
}
void
screen_menu(int value)
{
char* name = 0;
switch (value) {
case 'a':
name = "data/al.obj";
break;
case 's':
name = "data/soccerball.obj";
break;
case 'd':
name = "data/dolphins.obj";
break;
case 'f':
name = "data/flowers.obj";
break;
case 'j':
name = "data/f-16.obj";
break;
case 'p':
name = "data/porsche.obj";
break;
case 'r':
name = "data/rose+vase.obj";
break;
}
if (name) {
pmodel = glmReadOBJ(name);
if (!pmodel) exit(0);
glmUnitize(pmodel);
glmFacetNormals(pmodel);
glmVertexNormals(pmodel, 90.0);
}
redisplay_all();
}
void
command_reshape(int width, int height)
{
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0, width, height, 0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glClearColor(0.0, 0.0, 0.0, 0.0);
}
void
command_display(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glColor3ub(255, 255, 255);
setfont("helvetica", 18);
if (swapped) {
lookat[0].y = 120;
lookat[1].y = 120;
lookat[2].y = 120;
lookat[3].y = 120+40;
lookat[4].y = 120+40;
lookat[5].y = 120+40;
lookat[6].y = 120+80;
lookat[7].y = 120+80;
lookat[8].y = 120+80;
} else {
lookat[0].y = 80;
lookat[1].y = 80;
lookat[2].y = 80;
lookat[3].y = 80+40;
lookat[4].y = 80+40;
lookat[5].y = 80+40;
lookat[6].y = 80+80;
lookat[7].y = 80+80;
lookat[8].y = 80+80;
}
drawstr(30, light[0].y, "GLfloat pos[4] = {");
drawstr(230, light[0].y, ",");
drawstr(290, light[0].y, ",");
drawstr(350, light[0].y, ",");
drawstr(410, light[0].y, "};");
if (swapped)
drawstr(30, 80, "glLightfv(GL_LIGHT0, GL_POSITION, pos);");
else
drawstr(30, 200, "glLightfv(GL_LIGHT0, GL_POSITION, pos);");
drawstr(78, lookat[0].y, "gluLookAt(");
drawstr(230, lookat[0].y, ",");
drawstr(290, lookat[0].y, ",");
drawstr(350, lookat[0].y, ",");
drawstr(380, lookat[0].y, "<- eye");
drawstr(230, lookat[3].y, ",");
drawstr(290, lookat[3].y, ",");
drawstr(350, lookat[3].y, ",");
drawstr(380, lookat[3].y, "<- center");
drawstr(230, lookat[6].y, ",");
drawstr(290, lookat[6].y, ",");
drawstr(350, lookat[6].y, ");");
drawstr(380, lookat[6].y, "<- up");
cell_draw(&light[0]);
cell_draw(&light[1]);
cell_draw(&light[2]);
cell_draw(&light[3]);
cell_draw(&lookat[0]);
cell_draw(&lookat[1]);
cell_draw(&lookat[2]);
cell_draw(&lookat[3]);
cell_draw(&lookat[4]);
cell_draw(&lookat[5]);
cell_draw(&lookat[6]);
cell_draw(&lookat[7]);
cell_draw(&lookat[8]);
if (!selection) {
glColor3ub(255, 255, 0);
drawstr(10, 240,
"Click on the arguments and move the mouse to modify values.");
}
glutSwapBuffers();
}
int old_y;
void
command_mouse(int button, int state, int x, int y)
{
selection = 0;
if (state == GLUT_DOWN) {
/* mouse should only hit _one_ of the cells, so adding up all
the hits just propagates a single hit. */
selection += cell_hit(&light[0], x, y);
selection += cell_hit(&light[1], x, y);
selection += cell_hit(&light[2], x, y);
selection += cell_hit(&light[3], x, y);
selection += cell_hit(&lookat[0], x, y);
selection += cell_hit(&lookat[1], x, y);
selection += cell_hit(&lookat[2], x, y);
selection += cell_hit(&lookat[3], x, y);
selection += cell_hit(&lookat[4], x, y);
selection += cell_hit(&lookat[5], x, y);
selection += cell_hit(&lookat[6], x, y);
selection += cell_hit(&lookat[7], x, y);
selection += cell_hit(&lookat[8], x, y);
}
old_y = y;
redisplay_all();
}
void
command_motion(int x, int y)
{
cell_update(&light[0], old_y-y);
cell_update(&light[1], old_y-y);
cell_update(&light[2], old_y-y);
cell_update(&light[3], old_y-y);
cell_update(&lookat[0], old_y-y);
cell_update(&lookat[1], old_y-y);
cell_update(&lookat[2], old_y-y);
cell_update(&lookat[3], old_y-y);
cell_update(&lookat[4], old_y-y);
cell_update(&lookat[5], old_y-y);
cell_update(&lookat[6], old_y-y);
cell_update(&lookat[7], old_y-y);
cell_update(&lookat[8], old_y-y);
old_y = y;
redisplay_all();
}
void
command_menu(int value)
{
main_keyboard((unsigned char)value, 0, 0);
}
void
redisplay_all(void)
{
glutSetWindow(command);
glutPostRedisplay();
glutSetWindow(world);
world_reshape(sub_width, sub_height);
glutPostRedisplay();
glutSetWindow(screen);
screen_reshape(sub_width, sub_height);
glutPostRedisplay();
}
int
main(int argc, char** argv)
{
glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
glutInitWindowSize(512+GAP*3, 512+GAP*3);
glutInitWindowPosition(50, 50);
glutInit(&argc, argv);
window = glutCreateWindow("Light Positioning");
glutReshapeFunc(main_reshape);
glutDisplayFunc(main_display);
glutKeyboardFunc(main_keyboard);
world = glutCreateSubWindow(window, GAP, GAP, 256, 256);
glutReshapeFunc(world_reshape);
glutDisplayFunc(world_display);
glutKeyboardFunc(main_keyboard);
glutCreateMenu(world_menu);
glutAddMenuEntry("Toggle model", 'm');
glutAttachMenu(GLUT_RIGHT_BUTTON);
screen = glutCreateSubWindow(window, GAP+256+GAP, GAP, 256, 256);
glutReshapeFunc(screen_reshape);
glutDisplayFunc(screen_display);
glutKeyboardFunc(main_keyboard);
glutCreateMenu(screen_menu);
glutAddMenuEntry("Models", 0);
glutAddMenuEntry("", 0);
glutAddMenuEntry("Soccerball", 's');
glutAddMenuEntry("Al Capone", 'a');
glutAddMenuEntry("F-16 Jet", 'j');
glutAddMenuEntry("Dolphins", 'd');
glutAddMenuEntry("Flowers", 'f');
glutAddMenuEntry("Porsche", 'p');
glutAddMenuEntry("Rose", 'r');
glutAddMenuEntry("Sphere", 'h');
glutAttachMenu(GLUT_RIGHT_BUTTON);
command = glutCreateSubWindow(window, GAP+256+GAP, GAP+256+GAP, 256, 256);
glutReshapeFunc(command_reshape);
glutDisplayFunc(command_display);
glutMotionFunc(command_motion);
glutMouseFunc(command_mouse);
glutKeyboardFunc(main_keyboard);
glutCreateMenu(command_menu);
glutAddMenuEntry("Light Positioning", 0);
glutAddMenuEntry("", 0);
glutAddMenuEntry("[s] Swap lookat/position calls", 's');
glutAddMenuEntry("[r] Reset parameters", 'r');
glutAddMenuEntry("", 0);
glutAddMenuEntry("Quit", 27);
glutAttachMenu(GLUT_RIGHT_BUTTON);
redisplay_all();
glutMainLoop();
return 0;
}