path: root/progs/tests/debugger.c

/*
 * Test the GL_MESA_program_debug extension
 */


#include <assert.h>
#include <ctype.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define GL_GLEXT_PROTOTYPES
#include <GL/glut.h>


/*
 * Print the string with line numbers
 */
static void list_program(const GLubyte *string, GLsizei len)
{
   const char *c = (const char *) string;
   int i, line = 1, printNumber = 1;

   for (i = 0; i < len; i++) {
      if (printNumber) {
         printf("%3d ", line);
         printNumber = 0;
      }
      if (*c == '\n') {
         line++;
         printNumber = 1;
      }
      putchar(*c);
      c++;
   }
   putchar('\n');
}


/*
 * Return the line number and column number that corresponds to the
 * given program position.  Also return a null-terminated copy of that
 * line of the program string.
 */
static const GLubyte *
find_line_column(const GLubyte *string, const GLubyte *pos,
                 GLint *line, GLint *col)
{
   const GLubyte *lineStart = string;
   const GLubyte *p = string;
   GLubyte *s;
   int len;

   *line = 1;

   while (p != pos) {
      if (*p == (GLubyte) '\n') {
         (*line)++;
         lineStart = p + 1;
      }
      p++;
   }

   *col = (pos - lineStart) + 1;

   /* return copy of this line */
   while (*p != 0 && *p != '\n')
      p++;
   len = p - lineStart;
   s = (GLubyte *) malloc(len + 1);
   memcpy(s, lineStart, len);
   s[len] = 0;

   return s;
}


#define ARB_VERTEX_PROGRAM    1
#define ARB_FRAGMENT_PROGRAM  2
#define NV_VERTEX_PROGRAM     3
#define NV_FRAGMENT_PROGRAM   4


struct breakpoint {
   enum {PIXEL, LINE} type;
   int x, y;
   int line;
   GLboolean enabled;
};

#define MAX_BREAKPOINTS 100
static struct breakpoint Breakpoints[MAX_BREAKPOINTS];
static int NumBreakpoints = 0;



/*
 * Interactive debugger
 */
static void Debugger2(GLenum target, GLvoid *data)
{
   static GLuint skipCount = 0;
   const GLubyte *ln;
   GLint pos, line, column;
   GLint id;
   int progType;
   GLint len;
   GLubyte *program;
   GLboolean stop;
   int i;

   /* Sigh, GL_VERTEX_PROGRAM_ARB == GL_VERTEX_PROGRAM_NV so it's a bit
    * hard to distinguish between them.
    */
   if (target == GL_FRAGMENT_PROGRAM_ARB)
      progType = ARB_FRAGMENT_PROGRAM;
   else if (target == GL_FRAGMENT_PROGRAM_NV)
      progType = NV_FRAGMENT_PROGRAM;
   else
      progType = NV_VERTEX_PROGRAM;         

   /* Until we hit zero, continue rendering */
   if (skipCount > 0) {
      skipCount--;
      return;
   }

   /* Get id of the program and current position */
   switch (progType) {
   case ARB_FRAGMENT_PROGRAM:
      glGetProgramivARB(GL_FRAGMENT_PROGRAM_ARB, GL_PROGRAM_BINDING_ARB, &id);
      glGetIntegerv(GL_FRAGMENT_PROGRAM_POSITION_MESA, &pos);
      break;
   case NV_FRAGMENT_PROGRAM:
      glGetIntegerv(GL_FRAGMENT_PROGRAM_BINDING_NV, &id);
      glGetIntegerv(GL_FRAGMENT_PROGRAM_POSITION_MESA, &pos);
      break;
   case ARB_VERTEX_PROGRAM:
      glGetProgramivARB(GL_VERTEX_PROGRAM_ARB, GL_PROGRAM_BINDING_ARB, &id);
      glGetIntegerv(GL_VERTEX_PROGRAM_POSITION_MESA, &pos);
      break;
   case NV_VERTEX_PROGRAM:
      glGetIntegerv(GL_VERTEX_PROGRAM_BINDING_NV, &id);
      glGetIntegerv(GL_VERTEX_PROGRAM_POSITION_MESA, &pos);
      break;
   default:
      abort();
   }

   /* get program string */
   if (progType == ARB_VERTEX_PROGRAM ||
       progType == ARB_FRAGMENT_PROGRAM)
      glGetProgramivARB(target, GL_PROGRAM_LENGTH_ARB, &len);
   else
      glGetProgramivNV(id, GL_PROGRAM_LENGTH_NV, &len);
   program = malloc(len + 1);
   if (progType == ARB_VERTEX_PROGRAM ||
       progType == ARB_FRAGMENT_PROGRAM)
      glGetProgramStringARB(target, GL_PROGRAM_STRING_ARB, program);
   else
      glGetProgramStringNV(id, GL_PROGRAM_STRING_NV, program);


   /* Get current line number, column, line string */
   ln = find_line_column(program, program + pos, &line, &column);

   /* test breakpoints */   
   if (NumBreakpoints > 0)
      stop = GL_FALSE;
   else
      stop = GL_TRUE;
   for (i = 0; i < NumBreakpoints; i++) {
      if (Breakpoints[i].enabled) {
         switch (Breakpoints[i].type) {
            case PIXEL:
               if (progType == ARB_FRAGMENT_PROGRAM) {

               }
               else if (progType == NV_FRAGMENT_PROGRAM) {
                  GLfloat pos[4];
                  int px, py;
                  glGetProgramRegisterfvMESA(GL_FRAGMENT_PROGRAM_NV,
                                             6, (GLubyte *) "f[WPOS]", pos);
                  px = (int) pos[0];
                  py = (int) pos[1];
                  printf("%d, %d\n", px, py);
                  if (px == Breakpoints[i].x &&
                      py == Breakpoints[i].y) {
                     printf("Break at pixel (%d, %d)\n", px, py);
                     stop = GL_TRUE;
                  }
               }
               break;
            case LINE:
               if (line == Breakpoints[i].line) {
                  /* hit a breakpoint! */
                  printf("Break at line %d\n", line);
                  stop = GL_TRUE;
               }
               break;
         }
      }
   }
   if (!stop) {
      free(program);
      return;
   }

   printf("%d: %s\n", line, ln);

   /* get commands from stdin */
   while (1) {
      char command[1000], *cmd;

      /* print prompt and get command */
      printf("(%s %d) ", (target == GL_VERTEX_PROGRAM_ARB ? "vert" : "frag"),
             line);
      fgets(command, 999, stdin);

      /* skip leading whitespace */
      for (cmd = command; cmd[0] == ' '; cmd++)
         ;

      if (!cmd[0])
         /* nothing (repeat the previous cmd?) */
         continue;

      switch (cmd[0]) {
         case 's':
            /* skip N instructions */
            i = atoi(cmd + 2);
            skipCount = i;
            printf("Skipping %d instructions\n", i);
            return;
         case 'n':
            /* next */
            return;
         case 'c':
            return;
         case 'd':
            /* dump machine state */
            if (progType == NV_FRAGMENT_PROGRAM) {
               static const char *inRegs[] = {
                  "f[WPOS]", "f[COL0]", "f[COL1]", "f[FOGC]",
                  "f[TEX0]", "f[TEX1]", "f[TEX2]", "f[TEX3]",
                  NULL
               };
               static const char *outRegs[] = {
                  "o[COLR]", "o[COLH]", "o[DEPR]", NULL
               };
               GLfloat v[4];
               int i;
               printf("Fragment input attributes:\n");
               for (i = 0; inRegs[i]; i++) {
                  glGetProgramRegisterfvMESA(GL_FRAGMENT_PROGRAM_NV,
                                             strlen(inRegs[i]),
                                             (const GLubyte *) inRegs[i], v);
                  printf("  %s: %g, %g, %g, %g\n", inRegs[i],
                         v[0], v[1], v[2], v[3]);
               }
               printf("Fragment output attributes:\n");
               for (i = 0; outRegs[i]; i++) {
                  glGetProgramRegisterfvMESA(GL_FRAGMENT_PROGRAM_NV,
                                             strlen(outRegs[i]),
                                             (const GLubyte *) outRegs[i], v);
                  printf("  %s: %g, %g, %g, %g\n", outRegs[i],
                         v[0], v[1], v[2], v[3]);
               }
               printf("Temporaries:\n");
               for (i = 0; i < 4; i++) {
                  char temp[100];
                  GLfloat v[4];
                  sprintf(temp, "R%d", i);
                  glGetProgramRegisterfvMESA(GL_FRAGMENT_PROGRAM_NV,
                                             strlen(temp),
                                             (const GLubyte *) temp, v);
                  printf("  %s: %g, %g, %g, %g\n", temp, v[0],v[1],v[2],v[3]);
               }
            }
            else if (progType == NV_VERTEX_PROGRAM) {
               GLfloat v[4];
               int i;
               static const char *inRegs[] = {
                  "v[OPOS]", "v[WGHT]", "v[NRML]", "v[COL0]",
                  "v[COL1]", "v[FOGC]", "v[6]", "v[7]",
                  "v[TEX0]", "v[TEX1]", "v[TEX2]", "v[TEX3]",
                  "v[TEX4]", "v[TEX5]", "v[TEX6]", "v[TEX7]",
                  NULL
               };
               static const char *outRegs[] = {
                  "o[HPOS]", "o[COL0]", "o[COL1]", "o[BFC0]",
                  "o[BFC1]", "o[FOGC]", "o[PSIZ]",
                  "o[TEX0]", "o[TEX1]", "o[TEX2]", "o[TEX3]",
                  "o[TEX4]", "o[TEX5]", "o[TEX6]", "o[TEX7]",
                  NULL
               };
               printf("Vertex input attributes:\n");
               for (i = 0; inRegs[i]; i++) {
                  glGetProgramRegisterfvMESA(GL_VERTEX_PROGRAM_NV,
                                             strlen(inRegs[i]),
                                             (const GLubyte *) inRegs[i], v);
                  printf("  %s: %g, %g, %g, %g\n", inRegs[i],
                         v[0], v[1], v[2], v[3]);
               }
               printf("Vertex output attributes:\n");
               for (i = 0; outRegs[i]; i++) {
                  glGetProgramRegisterfvMESA(GL_VERTEX_PROGRAM_NV,
                                             strlen(outRegs[i]),
                                             (const GLubyte *) outRegs[i], v);
                  printf("  %s: %g, %g, %g, %g\n", outRegs[i],
                         v[0], v[1], v[2], v[3]);
               }
               printf("Temporaries:\n");
               for (i = 0; i < 4; i++) {
                  char temp[100];
                  GLfloat v[4];
                  sprintf(temp, "R%d", i);
                  glGetProgramRegisterfvMESA(GL_VERTEX_PROGRAM_NV,
                                             strlen(temp),
                                             (const GLubyte *) temp, v);
                  printf("  %s: %g, %g, %g, %g\n", temp, v[0],v[1],v[2],v[3]);
               }
            }
            break;
         case 'l':
            /* list */
            list_program(program, len);
            break;
         case 'p':
            /* print */
            {
               GLfloat v[4];
               char *c;
               cmd++;
               while (*cmd == ' ')
                  cmd++;
               c = cmd;
               while (*c) {
                  if (*c == '\n' || *c == '\r')
                     *c = 0;
                  else
                     c++;
               }
               glGetProgramRegisterfvMESA(target, strlen(cmd),
                                          (const GLubyte *) cmd, v);
               if (glGetError() == GL_NO_ERROR)
                  printf("%s = %g, %g, %g, %g\n", cmd, v[0], v[1], v[2], v[3]);
               else
                  printf("Invalid expression\n");
            }
            break;
         case 'b':
            if (cmd[1] == ' ' && isdigit(cmd[2])) {
               char *comma = strchr(cmd, ',');
               if (comma) {
                  /* break at pixel */
                  int x = atoi(cmd + 2);
                  int y = atoi(comma + 1);
                  if (NumBreakpoints < MAX_BREAKPOINTS) {
                     Breakpoints[NumBreakpoints].type = PIXEL;
                     Breakpoints[NumBreakpoints].x = x;
                     Breakpoints[NumBreakpoints].y = y;
                     Breakpoints[NumBreakpoints].enabled = GL_TRUE;
                     NumBreakpoints++;
                     printf("Breakpoint %d: break at pixel (%d, %d)\n",
                            NumBreakpoints, x, y);
                  }
               }
               else {
                  /* break at line */
                  int l = atoi(cmd + 2);
                  if (l && NumBreakpoints < MAX_BREAKPOINTS) {
                     Breakpoints[NumBreakpoints].type = LINE;
                     Breakpoints[NumBreakpoints].line = l;
                     Breakpoints[NumBreakpoints].enabled = GL_TRUE;
                     NumBreakpoints++;
                     printf("Breakpoint %d: break at line %d\n",
                            NumBreakpoints, l);
                  }
               }
            }
            else {
               /* list breakpoints */
               printf("Breakpoints:\n");
               for (i = 0; i < NumBreakpoints; i++) {
                  switch (Breakpoints[i].type) {
                  case LINE:
                     printf("  %d: break at line %d\n",
                            i + 1, Breakpoints[i].line);
                     break;
                  case PIXEL:
                     printf("  %d: break at pixel (%d, %d)\n",
                            i + 1, Breakpoints[i].x, Breakpoints[i].y);
                     break;
                  }
               }
            }
            break;
         case 'h':
            /* help */
            printf("Debugger commands:\n");
            printf("  b      list breakpoints\n");
            printf("  b N    break at line N\n");
            printf("  b x,y  break at pixel x,y\n");
            printf("  c      continue execution\n");
            printf("  d      display register values\n");
            printf("  h      help\n");
            printf("  l      list program\n");
            printf("  n      next instruction\n");
            printf("  p V    print value V\n");
            printf("  s N    skip N instructions\n");
            break;
         default:
            printf("Unknown command: %c\n", cmd[0]);
      }
   }
}


/*
 * Print current line, some registers, and continue.
 */
static void Debugger(GLenum target, GLvoid *data)
{
   GLint pos;
   const GLubyte *ln;
   GLint line, column;
   GLfloat v[4];

   assert(target == GL_FRAGMENT_PROGRAM_NV);

   glGetIntegerv(GL_FRAGMENT_PROGRAM_POSITION_MESA, &pos);

   ln = find_line_column((const GLubyte *) data, (const GLubyte *) data + pos,
                         &line, &column);
   printf("%d:%d: %s\n", line, column, (char *) ln);

   glGetProgramRegisterfvMESA(GL_FRAGMENT_PROGRAM_NV,
                              2, (const GLubyte *) "R0", v);
   printf("  R0 = %g, %g, %g, %g\n", v[0], v[1], v[2], v[3]);
   glGetProgramRegisterfvMESA(GL_FRAGMENT_PROGRAM_NV,
                              7, (const GLubyte *) "f[WPOS]", v);
   printf("  o[WPOS] = %g, %g, %g, %g\n", v[0], v[1], v[2], v[3]);
   glGetProgramRegisterfvMESA(GL_FRAGMENT_PROGRAM_NV,
                              7, (const GLubyte *) "o[COLR]", v);
   printf("  o[COLR] = %g, %g, %g, %g\n", v[0], v[1], v[2], v[3]);

   free((void *) ln);
}




/**********************************************************************/

static GLfloat Diffuse[4] = { 0.5, 0.5, 1.0, 1.0 };
static GLfloat Specular[4] = { 0.8, 0.8, 0.8, 1.0 };
static GLfloat LightPos[4] = { 0.0, 10.0, 20.0, 1.0 };
static GLfloat Delta = 1.0;

static GLuint FragProg;
static GLuint VertProg;
static GLboolean Anim = GL_TRUE;
static GLboolean Wire = GL_FALSE;
static GLboolean PixelLight = GL_TRUE;

static GLfloat Xrot = 0, Yrot = 0;


#define NAMED_PARAMETER4FV(prog, name, v)        \
  glProgramNamedParameter4fvNV(prog, strlen(name), (const GLubyte *) name, v)


static void Display( void )
{
   glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

   if (PixelLight) {
      NAMED_PARAMETER4FV(FragProg, "LightPos", LightPos);
      glEnable(GL_FRAGMENT_PROGRAM_NV);
      glEnable(GL_VERTEX_PROGRAM_NV);
      glDisable(GL_LIGHTING);
   }
   else {
      glLightfv(GL_LIGHT0, GL_POSITION, LightPos);
      glDisable(GL_FRAGMENT_PROGRAM_NV);
      glDisable(GL_VERTEX_PROGRAM_NV);
      glEnable(GL_LIGHTING);
   }

   glPushMatrix();
   glRotatef(Xrot, 1, 0, 0);
   glRotatef(Yrot, 0, 1, 0);

#if 1
   glutSolidSphere(2.0, 10, 5);
#else
   {
      GLUquadricObj *q = gluNewQuadric();
      gluQuadricNormals(q, GL_SMOOTH);
      gluQuadricTexture(q, GL_TRUE);
      glRotatef(90, 1, 0, 0);
      glTranslatef(0, 0, -1);
      gluCylinder(q, 1.0, 1.0, 2.0, 24, 1);
      gluDeleteQuadric(q);
   }
#endif

   glPopMatrix();

   glutSwapBuffers();
}


static void Idle(void)
{
   LightPos[0] += Delta;
   if (LightPos[0] > 25.0)
      Delta = -1.0;
   else if (LightPos[0] <- 25.0)
      Delta = 1.0;
   glutPostRedisplay();
}


static void Reshape( int width, int height )
{
   glViewport( 0, 0, width, height );
   glMatrixMode( GL_PROJECTION );
   glLoadIdentity();
   glFrustum( -1.0, 1.0, -1.0, 1.0, 5.0, 25.0 );
   /*glOrtho( -2.0, 2.0, -2.0, 2.0, 5.0, 25.0 );*/
   glMatrixMode( GL_MODELVIEW );
   glLoadIdentity();
   glTranslatef( 0.0, 0.0, -15.0 );
}


static void Key( unsigned char key, int x, int y )
{
   (void) x;
   (void) y;
   switch (key) {
     case ' ':
        Anim = !Anim;
        if (Anim)
           glutIdleFunc(Idle);
        else
           glutIdleFunc(NULL);
        break;
      case 'x':
         LightPos[0] -= 1.0;
         break;
      case 'X':
         LightPos[0] += 1.0;
         break;
      case 'w':
         Wire = !Wire;
         if (Wire)
            glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
         else
            glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
         break;
      case 'p':
         PixelLight = !PixelLight;
         if (PixelLight) {
            printf("Per-pixel lighting\n");
         }
         else {
            printf("Conventional lighting\n");
         }
         break;
      case 27:
         exit(0);
         break;
   }
   glutPostRedisplay();
}

static void SpecialKey( int key, int x, int y )
{
   const GLfloat step = 3.0;
   (void) x;
   (void) y;
   switch (key) {
      case GLUT_KEY_UP:
         Xrot -= step;
         break;
      case GLUT_KEY_DOWN:
         Xrot += step;
         break;
      case GLUT_KEY_LEFT:
         Yrot -= step;
         break;
      case GLUT_KEY_RIGHT:
         Yrot += step;
         break;
   }
   glutPostRedisplay();
}


static void Init( int argc, char *argv[] )
{
   static const char *fragProgramText =
      "!!FP1.0\n"
      "DECLARE Diffuse; \n"
      "DECLARE Specular; \n"
      "DECLARE LightPos; \n"

      "# Compute normalized LightPos, put it in R0\n"
      "DP3 R0.x, LightPos, LightPos;\n"
      "RSQ R0.y, R0.x;\n"
      "MUL R0, LightPos, R0.y;\n"

      "# Compute normalized normal, put it in R1\n"
      "DP3 R1, f[TEX0], f[TEX0]; \n"
      "RSQ R1.y, R1.x;\n"
      "MUL R1, f[TEX0], R1.y;\n"

      "# Compute dot product of light direction and normal vector\n"
      "DP3 R2, R0, R1;\n"

      "MUL R3, Diffuse, R2;    # diffuse attenuation\n"

      "POW R4, R2.x, {20.0}.x; # specular exponent\n"

      "MUL R5, Specular, R4;   # specular attenuation\n"

      "ADD o[COLR], R3, R5;    # add diffuse and specular colors\n"
      "END \n"
      ;

   static const char *vertProgramText =
      "!!VP1.0\n"
      "# typical modelview/projection transform\n"
      "DP4   o[HPOS].x, c[0], v[OPOS] ;\n"
      "DP4   o[HPOS].y, c[1], v[OPOS] ;\n"
      "DP4   o[HPOS].z, c[2], v[OPOS] ;\n"
      "DP4   o[HPOS].w, c[3], v[OPOS] ;\n"
      "# transform normal by inv transpose of modelview, put in tex0\n"
      "DP4   o[TEX0].x, c[4], v[NRML] ;\n"
      "DP4   o[TEX0].y, c[5], v[NRML] ;\n"
      "DP4   o[TEX0].z, c[6], v[NRML] ;\n"
      "DP4   o[TEX0].w, c[7], v[NRML] ;\n"
      "END\n";
   ;

   if (!glutExtensionSupported("GL_NV_vertex_program")) {
      printf("Sorry, this demo requires GL_NV_vertex_program\n");
      exit(1);
   }
   if (!glutExtensionSupported("GL_NV_fragment_program")) {
      printf("Sorry, this demo requires GL_NV_fragment_program\n");
      exit(1);
   }
         
   glGenProgramsNV(1, &FragProg);
   assert(FragProg > 0);
   glGenProgramsNV(1, &VertProg);
   assert(VertProg > 0);

   /*
    * Fragment program
    */
   glLoadProgramNV(GL_FRAGMENT_PROGRAM_NV, FragProg,
                   strlen(fragProgramText),
                   (const GLubyte *) fragProgramText);
   assert(glIsProgramNV(FragProg));
   glBindProgramNV(GL_FRAGMENT_PROGRAM_NV, FragProg);

   NAMED_PARAMETER4FV(FragProg, "Diffuse", Diffuse);
   NAMED_PARAMETER4FV(FragProg, "Specular", Specular);

   /*
    * Vertex program
    */
   glLoadProgramNV(GL_VERTEX_PROGRAM_NV, VertProg,
                   strlen(vertProgramText),
                   (const GLubyte *) vertProgramText);
   assert(glIsProgramNV(VertProg));
   glBindProgramNV(GL_VERTEX_PROGRAM_NV, VertProg);
   glTrackMatrixNV(GL_VERTEX_PROGRAM_NV, 0, GL_MODELVIEW_PROJECTION_NV, GL_IDENTITY_NV);
   glTrackMatrixNV(GL_VERTEX_PROGRAM_NV, 4, GL_MODELVIEW, GL_INVERSE_TRANSPOSE_NV);

   /*
    * Misc init
    */
   glClearColor(0.3, 0.3, 0.3, 0.0);
   glEnable(GL_DEPTH_TEST);
   glEnable(GL_LIGHT0);
   glEnable(GL_LIGHTING);
   glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, Diffuse);
   glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, Specular);
   glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, 20.0);

   printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
   printf("Press p to toggle between per-pixel and per-vertex lighting\n");

#ifdef GL_MESA_program_debug
   if (argc > 1 && strcmp(argv[1], "fragment") == 0) {
      printf(">> Debugging fragment program\n");
      glProgramCallbackMESA(GL_FRAGMENT_PROGRAM_ARB, Debugger2,
                            (GLvoid *) fragProgramText);
      glEnable(GL_FRAGMENT_PROGRAM_CALLBACK_MESA);
   }
   else {
      printf(">> Debugging vertex program\n");
      glProgramCallbackMESA(GL_VERTEX_PROGRAM_ARB, Debugger2,
                            (GLvoid *) fragProgramText);
      glEnable(GL_VERTEX_PROGRAM_CALLBACK_MESA);
   }
#endif
}


int main( int argc, char *argv[] )
{
   glutInit( &argc, argv );
   glutInitWindowPosition( 0, 0 );
   glutInitWindowSize( 200, 200 );
   glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
   glutCreateWindow(argv[0]);
   glutReshapeFunc( Reshape );
   glutKeyboardFunc( Key );
   glutSpecialFunc( SpecialKey );
   glutDisplayFunc( Display );
   if (Anim)
      glutIdleFunc(Idle);
   Init(argc, argv);
   glutMainLoop();
   return 0;
}