progs/demos/tessdemo.c

   1
   2 /*
   3  * A demo of the GLU polygon tesselation functions written by Bogdan Sikorski.
   4  * Updated for GLU 1.3 tessellation by Gareth Hughes <gareth@valinux.com>
   5  */
   6
   7 #include <GL/glut.h>
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11
  12 #define MAX_POINTS      256
  13 #define MAX_CONTOURS    32
  14 #define MAX_TRIANGLES   256
  15
  16 #ifndef GLCALLBACK
  17 #ifdef CALLBACK
  18 #define GLCALLBACK CALLBACK
  19 #else
  20 #define GLCALLBACK
  21 #endif
  22 #endif
  23
  24 #ifdef GLU_VERSION_1_2
  25
  26 typedef enum{ QUIT, TESSELATE, CLEAR } menu_entries;
  27 typedef enum{ DEFINE, TESSELATED } mode_type;
  28
  29 static GLsizei          width, height;
  30 static GLuint           contour_cnt;
  31 static GLuint           triangle_cnt;
  32
  33 static mode_type        mode;
  34 static int              menu;
  35
  36 static GLuint           list_start;
  37
  38 static GLfloat          edge_color[3];
  39
  40 static struct {
  41    GLfloat      p[MAX_POINTS][2];
  42    GLuint       point_cnt;
  43 } contours[MAX_CONTOURS];
  44
  45 static struct {
  46    GLsizei      no;
  47    GLfloat      p[3][2];
  48    GLclampf     color[3][3];
  49 } triangles[MAX_TRIANGLES];
  50
  51
  52
  53 static void GLCALLBACK error_callback( GLenum err )
  54 {
  55    int          len, i;
  56    char const   *str;
  57
  58    glColor3f( 0.9, 0.9, 0.9 );
  59    glRasterPos2i( 5, 5 );
  60
  61    str = (const char *) gluErrorString( err );
  62    len = strlen( str );
  63
  64    for ( i = 0 ; i < len ; i++ ) {
  65       glutBitmapCharacter( GLUT_BITMAP_9_BY_15, str[i] );
  66    }
  67 }
  68
  69 static void GLCALLBACK begin_callback( GLenum mode )
  70 {
  71    /* Allow multiple triangles to be output inside the begin/end pair. */
  72    triangle_cnt = 0;
  73    triangles[triangle_cnt].no = 0;
  74 }
  75
  76 static void GLCALLBACK edge_callback( GLenum flag )
  77 {
  78    /* Persist the edge flag across triangles. */
  79    if ( flag == GL_TRUE ) {
  80       edge_color[0] = 1.0;
  81       edge_color[1] = 1.0;
  82       edge_color[2] = 0.5;
  83    } else {
  84       edge_color[0] = 1.0;
  85       edge_color[1] = 0.0;
  86       edge_color[2] = 0.0;
  87    }
  88 }
  89
  90 static void GLCALLBACK end_callback()
  91 {
  92    GLuint       i;
  93
  94    glBegin( GL_LINES );
  95
  96    /* Output the three edges of each triangle as lines colored
  97       according to their edge flag. */
  98    for ( i = 0 ; i < triangle_cnt ; i++ ) {
  99       glColor3f( triangles[i].color[0][0],
 100                  triangles[i].color[0][1],
 101                  triangles[i].color[0][2] );
 102
 103       glVertex2f( triangles[i].p[0][0], triangles[i].p[0][1] );
 104       glVertex2f( triangles[i].p[1][0], triangles[i].p[1][1] );
 105
 106       glColor3f( triangles[i].color[1][0],
 107                  triangles[i].color[1][1],
 108                  triangles[i].color[1][2] );
 109
 110       glVertex2f( triangles[i].p[1][0], triangles[i].p[1][1] );
 111       glVertex2f( triangles[i].p[2][0], triangles[i].p[2][1] );
 112
 113       glColor3f( triangles[i].color[2][0],
 114                  triangles[i].color[2][1],
 115                  triangles[i].color[2][2] );
 116
 117       glVertex2f( triangles[i].p[2][0], triangles[i].p[2][1] );
 118       glVertex2f( triangles[i].p[0][0], triangles[i].p[0][1] );
 119    }
 120
 121    glEnd();
 122 }
 123
 124 static void GLCALLBACK vertex_callback( void *data )
 125 {
 126    GLsizei      no;
 127    GLfloat      *p;
 128
 129    p = (GLfloat *) data;
 130    no = triangles[triangle_cnt].no;
 131
 132    triangles[triangle_cnt].p[no][0] = p[0];
 133    triangles[triangle_cnt].p[no][1] = p[1];
 134
 135    triangles[triangle_cnt].color[no][0] = edge_color[0];
 136    triangles[triangle_cnt].color[no][1] = edge_color[1];
 137    triangles[triangle_cnt].color[no][2] = edge_color[2];
 138
 139    /* After every three vertices, initialize the next triangle. */
 140    if ( ++(triangles[triangle_cnt].no) == 3 ) {
 141       triangle_cnt++;
 142       triangles[triangle_cnt].no = 0;
 143    }
 144 }
 145
 146 static void GLCALLBACK combine_callback( GLdouble coords[3],
 147                                          GLdouble *vertex_data[4],
 148                                          GLfloat weight[4], void **data )
 149 {
 150    GLfloat      *vertex;
 151
 152    vertex = (GLfloat *) malloc( 2 * sizeof(GLfloat) );
 153
 154    vertex[0] = (GLfloat) coords[0];
 155    vertex[1] = (GLfloat) coords[1];
 156
 157    *data = vertex;
 158 }
 159
 160
 161 static void set_screen_wh( GLsizei w, GLsizei h )
 162 {
 163    width = w;
 164    height = h;
 165 }
 166
 167 typedef void (GLAPIENTRY *callback_t)();
 168
 169 static void tesse( void )
 170 {
 171    GLUtesselator        *tobj;
 172    GLdouble             data[3];
 173    GLuint               i, j, point_cnt;
 174
 175    list_start = glGenLists( 2 );
 176
 177    tobj = gluNewTess();
 178
 179    if ( tobj != NULL ) {
 180       gluTessNormal( tobj, 0.0, 0.0, 1.0 );
 181       gluTessCallback( tobj, GLU_TESS_BEGIN, (callback_t) glBegin );
 182       gluTessCallback( tobj, GLU_TESS_VERTEX, (callback_t) glVertex2fv );
 183       gluTessCallback( tobj, GLU_TESS_END, (callback_t) glEnd );
 184       gluTessCallback( tobj, GLU_TESS_ERROR, (callback_t) error_callback );
 185       gluTessCallback( tobj, GLU_TESS_COMBINE, (callback_t) combine_callback );
 186
 187       glNewList( list_start, GL_COMPILE );
 188       gluBeginPolygon( tobj );
 189
 190       for ( j = 0 ; j <= contour_cnt ; j++ ) {
 191          point_cnt = contours[j].point_cnt;
 192          gluNextContour( tobj, GLU_UNKNOWN );
 193
 194          for ( i = 0 ; i < point_cnt ; i++ ) {
 195             data[0] = (GLdouble)( contours[j].p[i][0] );
 196             data[1] = (GLdouble)( contours[j].p[i][1] );
 197             data[2] = 0.0;
 198             gluTessVertex( tobj, data, contours[j].p[i] );
 199          }
 200       }
 201
 202       gluEndPolygon( tobj );
 203       glEndList();
 204
 205       gluTessCallback( tobj, GLU_TESS_BEGIN, (callback_t) begin_callback );
 206       gluTessCallback( tobj, GLU_TESS_VERTEX, (callback_t) vertex_callback );
 207       gluTessCallback( tobj, GLU_TESS_END, (callback_t) end_callback );
 208       gluTessCallback( tobj, GLU_TESS_EDGE_FLAG, (callback_t) edge_callback );
 209
 210       glNewList( list_start + 1, GL_COMPILE );
 211       gluBeginPolygon( tobj );
 212
 213       for ( j = 0 ; j <= contour_cnt ; j++ ) {
 214          point_cnt = contours[j].point_cnt;
 215          gluNextContour( tobj, GLU_UNKNOWN );
 216
 217          for ( i = 0 ; i < point_cnt ; i++ ) {
 218             data[0] = (GLdouble)( contours[j].p[i][0] );
 219             data[1] = (GLdouble)( contours[j].p[i][1] );
 220             data[2] = 0.0;
 221             gluTessVertex( tobj, data, contours[j].p[i] );
 222          }
 223       }
 224
 225       gluEndPolygon( tobj );
 226       glEndList();
 227
 228       gluDeleteTess( tobj );
 229
 230       glutMouseFunc( NULL );
 231       mode = TESSELATED;
 232    }
 233 }
 234
 235 static void left_down( int x1, int y1 )
 236 {
 237    GLfloat      P[2];
 238    GLuint       point_cnt;
 239
 240    /* translate GLUT into GL coordinates */
 241
 242    P[0] = x1;
 243    P[1] = height - y1;
 244
 245    point_cnt = contours[contour_cnt].point_cnt;
 246
 247    contours[contour_cnt].p[point_cnt][0] = P[0];
 248    contours[contour_cnt].p[point_cnt][1] = P[1];
 249
 250    glBegin( GL_LINES );
 251
 252    if ( point_cnt ) {
 253       glVertex2fv( contours[contour_cnt].p[point_cnt-1] );
 254       glVertex2fv( P );
 255    } else {
 256       glVertex2fv( P );
 257       glVertex2fv( P );
 258    }
 259
 260    glEnd();
 261    glFinish();
 262
 263    contours[contour_cnt].point_cnt++;
 264 }
 265
 266 static void middle_down( int x1, int y1 )
 267 {
 268    GLuint       point_cnt;
 269    (void) x1;
 270    (void) y1;
 271
 272    point_cnt = contours[contour_cnt].point_cnt;
 273
 274    if ( point_cnt > 2 ) {
 275       glBegin( GL_LINES );
 276
 277       glVertex2fv( contours[contour_cnt].p[0] );
 278       glVertex2fv( contours[contour_cnt].p[point_cnt-1] );
 279
 280       contours[contour_cnt].p[point_cnt][0] = -1;
 281
 282       glEnd();
 283       glFinish();
 284
 285       contour_cnt++;
 286       contours[contour_cnt].point_cnt = 0;
 287    }
 288 }
 289
 290 static void mouse_clicked( int button, int state, int x, int y )
 291 {
 292    x -= x%10;
 293    y -= y%10;
 294
 295    switch ( button ) {
 296    case GLUT_LEFT_BUTTON:
 297       if ( state == GLUT_DOWN ) {
 298          left_down( x, y );
 299       }
 300       break;
 301    case GLUT_MIDDLE_BUTTON:
 302       if ( state == GLUT_DOWN ) {
 303          middle_down( x, y );
 304       }
 305       break;
 306    }
 307 }
 308
 309 static void display( void )
 310 {
 311    GLuint i,j;
 312    GLsizei ii, jj;
 313    GLuint point_cnt;
 314
 315    glClear( GL_COLOR_BUFFER_BIT );
 316
 317    switch ( mode ) {
 318    case DEFINE:
 319       /* draw grid */
 320       glColor3f( 0.6, 0.5, 0.5 );
 321
 322       glBegin( GL_LINES );
 323
 324       for ( ii = 0 ; ii < width ; ii += 10 ) {
 325          for ( jj = 0 ; jj < height ; jj += 10 ) {
 326             glVertex2i( 0, jj );
 327             glVertex2i( width, jj );
 328             glVertex2i( ii, height );
 329             glVertex2i( ii, 0 );
 330          }
 331       }
 332
 333       glEnd();
 334
 335       glColor3f( 1.0, 1.0, 0.0 );
 336
 337       for ( i = 0 ; i <= contour_cnt ; i++ ) {
 338          point_cnt = contours[i].point_cnt;
 339
 340          glBegin( GL_LINES );
 341
 342          switch ( point_cnt ) {
 343          case 0:
 344             break;
 345          case 1:
 346             glVertex2fv( contours[i].p[0] );
 347             glVertex2fv( contours[i].p[0] );
 348             break;
 349          case 2:
 350             glVertex2fv( contours[i].p[0] );
 351             glVertex2fv( contours[i].p[1] );
 352             break;
 353          default:
 354             --point_cnt;
 355             for ( j = 0 ; j < point_cnt ; j++ ) {
 356                glVertex2fv( contours[i].p[j] );
 357                glVertex2fv( contours[i].p[j+1] );
 358             }
 359             if ( contours[i].p[j+1][0] == -1 ) {
 360                glVertex2fv( contours[i].p[0] );
 361                glVertex2fv( contours[i].p[j] );
 362             }
 363             break;
 364          }
 365
 366          glEnd();
 367       }
 368
 369       glFinish();
 370       break;
 371
 372    case TESSELATED:
 373       /* draw triangles */
 374       glColor3f( 0.7, 0.7, 0.0 );
 375       glCallList( list_start );
 376
 377       glLineWidth( 2.0 );
 378       glCallList( list_start + 1 );
 379       glLineWidth( 1.0 );
 380
 381       glFlush();
 382       break;
 383    }
 384
 385    glColor3f( 1.0, 1.0, 0.0 );
 386 }
 387
 388 static void clear( void )
 389 {
 390    contour_cnt = 0;
 391    contours[0].point_cnt = 0;
 392    triangle_cnt = 0;
 393
 394    glutMouseFunc( mouse_clicked );
 395
 396    mode = DEFINE;
 397
 398    glDeleteLists( list_start, 2 );
 399    list_start = 0;
 400 }
 401
 402 static void quit( void )
 403 {
 404    exit( 0 );
 405 }
 406
 407 static void menu_selected( int entry )
 408 {
 409    switch ( entry ) {
 410    case CLEAR:
 411       clear();
 412       break;
 413    case TESSELATE:
 414       tesse();
 415       break;
 416    case QUIT:
 417       quit();
 418       break;
 419    }
 420
 421    glutPostRedisplay();
 422 }
 423
 424 static void key_pressed( unsigned char key, int x, int y )
 425 {
 426    (void) x;
 427    (void) y;
 428
 429    switch ( key ) {
 430    case 'c':
 431    case 'C':
 432       clear();
 433       break;
 434    case 't':
 435    case 'T':
 436       tesse();
 437       break;
 438    case 27:
 439    case 'q':
 440    case 'Q':
 441       quit();
 442       break;
 443    }
 444
 445    glutPostRedisplay();
 446 }
 447
 448 static void myinit( void )
 449 {
 450    /* clear background to gray */
 451    glClearColor( 0.4, 0.4, 0.4, 0.0 );
 452    glShadeModel( GL_FLAT );
 453    glPolygonMode( GL_FRONT, GL_FILL );
 454
 455    menu = glutCreateMenu( menu_selected );
 456
 457    glutAddMenuEntry( "clear", CLEAR );
 458    glutAddMenuEntry( "tesselate", TESSELATE );
 459    glutAddMenuEntry( "quit", QUIT );
 460
 461    glutAttachMenu( GLUT_RIGHT_BUTTON );
 462
 463    glutMouseFunc( mouse_clicked );
 464    glutKeyboardFunc( key_pressed );
 465
 466    contour_cnt = 0;
 467    mode = DEFINE;
 468 }
 469
 470 static void reshape( GLsizei w, GLsizei h )
 471 {
 472    glViewport( 0, 0, w, h );
 473
 474    glMatrixMode( GL_PROJECTION );
 475    glLoadIdentity();
 476    glOrtho( 0.0, (GLdouble)w, 0.0, (GLdouble)h, -1.0, 1.0 );
 477
 478    glMatrixMode( GL_MODELVIEW );
 479    glLoadIdentity();
 480
 481    set_screen_wh( w, h );
 482 }
 483
 484 #endif
 485
 486
 487 static void usage( void )
 488 {
 489    printf( "Use left mouse button to place vertices.\n" );
 490    printf( "Press middle mouse button when done.\n" );
 491    printf( "Select tesselate from the pop-up menu.\n" );
 492 }
 493
 494
 495 int main( int argc, char **argv )
 496 {
 497    const char *version = (const char *) gluGetString( GLU_VERSION );
 498    printf( "GLU version string: %s\n", version );
 499    if ( strstr( version, "1.0" ) || strstr( version, "1.1" ) ) {
 500       fprintf( stderr, "Sorry, this demo reqiures GLU 1.2 or later.\n" );
 501       exit( 1 );
 502    }
 503
 504    usage();
 505
 506    glutInit( &argc, argv );
 507    glutInitDisplayMode( GLUT_SINGLE | GLUT_RGB );
 508    glutInitWindowPosition(0, 0);
 509    glutInitWindowSize( 400, 400 );
 510    glutCreateWindow( argv[0] );
 511
 512    /* GH: Bit of a hack...
 513     */
 514 #ifdef GLU_VERSION_1_2
 515    myinit();
 516
 517    glutDisplayFunc( display );
 518    glutReshapeFunc( reshape );
 519
 520    glutMainLoop();
 521 #endif
 522
 523    return 0;
 524 }