progs/demos/fogcoord.c

   1 /*
   2  * EXT_fog_coord.
   3  *
   4  * Based on glutskel.c by Brian Paul
   5  * and NeHe's Volumetric fog tutorial!
   6  *
   7  * Daniel Borca
   8  */
   9
  10
  11 #include <stdio.h>
  12 #include <stdlib.h>
  13 #include <math.h>
  14 #include <GL/glut.h>
  15
  16 #include "readtex.c" /* the compulsory hack  */
  17
  18 #define TEXTURE_FILE "../images/bw.rgb"
  19
  20 #define ARRAYS 0     /* use glDrawElements   */
  21
  22 #define VERBOSE 1    /* tell me what happens */
  23
  24 #define DEPTH 15.0f
  25
  26 typedef void (GLAPIENTRYP GLFOGCOORDFEXTPROC) (GLfloat f);
  27 typedef void (GLAPIENTRYP GLFOGCOORDPOINTEREXTPROC) (GLenum, GLsizei, const GLvoid *);
  28
  29 static GLFOGCOORDFEXTPROC glFogCoordf_ext;
  30 static GLFOGCOORDPOINTEREXTPROC glFogCoordPointer_ext;
  31 static GLboolean have_fog_coord;
  32
  33 static GLfloat camz;
  34 static GLuint texture[1];
  35
  36 static GLint fogMode;
  37 static GLboolean fogCoord;
  38 static GLfloat fogDensity = 0.75;
  39 static GLfloat fogStart = 1.0, fogEnd = 40.0;
  40 static GLfloat fogColor[4] = {0.6f, 0.3f, 0.0f, 1.0f};
  41
  42
  43 void APIENTRY glFogCoordf_nop (GLfloat f)
  44 {
  45  (void)f;
  46 }
  47
  48
  49 static int BuildTexture (const char *filename, GLuint texid[])
  50 {
  51  GLubyte *tex_data;
  52  GLenum tex_format;
  53  GLint tex_width, tex_height;
  54
  55  tex_data = LoadRGBImage(filename, &tex_width, &tex_height, &tex_format);
  56  if (tex_data == NULL) {
  57     return -1;
  58  }
  59
  60  {
  61   GLint tex_max;
  62   glGetIntegerv(GL_MAX_TEXTURE_SIZE, &tex_max);
  63   if ((tex_width > tex_max) || (tex_height > tex_max)) {
  64      return -1;
  65   }
  66  }
  67
  68  glGenTextures(1, texid);
  69
  70  glBindTexture(GL_TEXTURE_2D, texid[0]);
  71  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  72  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  73
  74  glTexImage2D(GL_TEXTURE_2D, 0, tex_format, tex_width, tex_height, 0, tex_format, GL_UNSIGNED_BYTE, tex_data);
  75
  76  return 0;
  77 }
  78
  79
  80 static int SetFogMode (GLint fogMode)
  81 {
  82  fogMode &= 3;
  83  switch (fogMode) {
  84         case 0:
  85              glDisable(GL_FOG);
  86 #if VERBOSE
  87              printf("fog(disable)\n");
  88 #endif
  89              break;
  90         case 1:
  91              glEnable(GL_FOG);
  92              glFogi(GL_FOG_MODE, GL_LINEAR);
  93              glFogf(GL_FOG_START, fogStart);
  94              glFogf(GL_FOG_END, fogEnd);
  95 #if VERBOSE
  96              printf("fog(GL_LINEAR, %.2f, %.2f)\n", fogStart, fogEnd);
  97 #endif
  98              break;
  99         case 2:
 100              glEnable(GL_FOG);
 101              glFogi(GL_FOG_MODE, GL_EXP);
 102              glFogf(GL_FOG_DENSITY, fogDensity);
 103 #if VERBOSE
 104              printf("fog(GL_EXP, %.2f)\n", fogDensity);
 105 #endif
 106              break;
 107         case 3:
 108              glEnable(GL_FOG);
 109              glFogi(GL_FOG_MODE, GL_EXP2);
 110              glFogf(GL_FOG_DENSITY, fogDensity);
 111 #if VERBOSE
 112              printf("fog(GL_EXP2, %.2f)\n", fogDensity);
 113 #endif
 114              break;
 115  }
 116  return fogMode;
 117 }
 118
 119
 120 static GLboolean SetFogCoord (GLboolean fogCoord)
 121 {
 122  glFogCoordf_ext = glFogCoordf_nop;
 123
 124  if (!have_fog_coord) {
 125 #if VERBOSE
 126     printf("fog(GL_FRAGMENT_DEPTH_EXT)%s\n", fogCoord ? " EXT_fog_coord not available!" : "");
 127 #endif
 128     return GL_FALSE;
 129  }
 130
 131  if (fogCoord) {
 132     glFogCoordf_ext = (GLFOGCOORDFEXTPROC)glutGetProcAddress("glFogCoordfEXT");
 133     glFogi(GL_FOG_COORDINATE_SOURCE_EXT, GL_FOG_COORDINATE_EXT);
 134 #if VERBOSE
 135     printf("fog(GL_FOG_COORDINATE_EXT)\n");
 136 #endif
 137  } else {
 138     glFogi(GL_FOG_COORDINATE_SOURCE_EXT, GL_FRAGMENT_DEPTH_EXT);
 139 #if VERBOSE
 140     printf("fog(GL_FRAGMENT_DEPTH_EXT)\n");
 141 #endif
 142  }
 143  return fogCoord;
 144 }
 145
 146
 147 #if ARRAYS
 148 /* could reuse vertices */
 149 static GLuint vertex_index[] = {
 150    /* Back */
 151    0, 1, 2, 3,
 152
 153    /* Floor */
 154    4, 5, 6, 7,
 155
 156    /* Roof */
 157    8, 9, 10, 11,
 158
 159    /* Right */
 160    12, 13, 14, 15,
 161
 162    /* Left */
 163    16, 17, 18, 19
 164 };
 165
 166 static GLfloat vertex_pointer[][3] = {
 167    /* Back */
 168    {-2.5f,-2.5f,-DEPTH}, { 2.5f,-2.5f,-DEPTH}, { 2.5f, 2.5f,-DEPTH}, {-2.5f, 2.5f,-DEPTH},
 169
 170    /* Floor */
 171    {-2.5f,-2.5f,-DEPTH}, { 2.5f,-2.5f,-DEPTH}, { 2.5f,-2.5f, DEPTH}, {-2.5f,-2.5f, DEPTH},
 172
 173    /* Roof */
 174    {-2.5f, 2.5f,-DEPTH}, { 2.5f, 2.5f,-DEPTH}, { 2.5f, 2.5f, DEPTH}, {-2.5f, 2.5f, DEPTH},
 175
 176    /* Right */
 177    { 2.5f,-2.5f, DEPTH}, { 2.5f, 2.5f, DEPTH}, { 2.5f, 2.5f,-DEPTH}, { 2.5f,-2.5f,-DEPTH},
 178
 179    /* Left */
 180    {-2.5f,-2.5f, DEPTH}, {-2.5f, 2.5f, DEPTH}, {-2.5f, 2.5f,-DEPTH}, {-2.5f,-2.5f,-DEPTH}
 181 };
 182
 183 static GLfloat texcoord_pointer[][2] = {
 184    /* Back */
 185    {0.0f, 0.0f}, {1.0f, 0.0f}, {1.0f, 1.0f}, {0.0f, 1.0f},
 186
 187    /* Floor */
 188    {0.0f, 0.0f}, {1.0f, 0.0f}, {1.0f, 1.0f}, {0.0f, 1.0f},
 189
 190    /* Roof */
 191    {0.0f, 0.0f}, {1.0f, 0.0f}, {1.0f, 1.0f}, {0.0f, 1.0f},
 192
 193    /* Right */
 194    {0.0f, 0.0f}, {0.0f, 1.0f}, {1.0f, 1.0f}, {1.0f, 0.0f},
 195
 196    /* Left */
 197    {0.0f, 0.0f}, {0.0f, 1.0f}, {1.0f, 1.0f}, {1.0f, 0.0f}
 198 };
 199
 200 static GLfloat fogcoord_pointer[][1] = {
 201    /* Back */
 202    {1.0f}, {1.0f}, {1.0f}, {1.0f},
 203
 204    /* Floor */
 205    {1.0f}, {1.0f}, {0.0f}, {0.0f},
 206
 207    /* Roof */
 208    {1.0f}, {1.0f}, {0.0f}, {0.0f},
 209
 210    /* Right */
 211    {0.0f}, {0.0f}, {1.0f}, {1.0f},
 212
 213    /* Left */
 214    {0.0f}, {0.0f}, {1.0f}, {1.0f}
 215 };
 216 #endif
 217
 218
 219 static void Display( void )
 220 {
 221    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 222    glLoadIdentity ();
 223
 224    glTranslatef(0.0f, 0.0f, camz);
 225
 226 #if ARRAYS
 227    glDrawElements(GL_QUADS, sizeof(vertex_index) / sizeof(vertex_index[0]), GL_UNSIGNED_INT, vertex_index);
 228 #else
 229    /* Back */
 230    glBegin(GL_QUADS);
 231    glFogCoordf_ext(1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-2.5f,-2.5f,-DEPTH);
 232    glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 2.5f,-2.5f,-DEPTH);
 233    glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 2.5f, 2.5f,-DEPTH);
 234    glFogCoordf_ext(1.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-2.5f, 2.5f,-DEPTH);
 235    glEnd();
 236
 237    /* Floor */
 238    glBegin(GL_QUADS);
 239    glFogCoordf_ext(1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-2.5f,-2.5f,-DEPTH);
 240    glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 2.5f,-2.5f,-DEPTH);
 241    glFogCoordf_ext(0.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 2.5f,-2.5f, DEPTH);
 242    glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-2.5f,-2.5f, DEPTH);
 243    glEnd();
 244
 245    /* Roof */
 246    glBegin(GL_QUADS);
 247    glFogCoordf_ext(1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-2.5f, 2.5f,-DEPTH);
 248    glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 2.5f, 2.5f,-DEPTH);
 249    glFogCoordf_ext(0.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 2.5f, 2.5f, DEPTH);
 250    glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-2.5f, 2.5f, DEPTH);
 251    glEnd();
 252
 253    /* Right */
 254    glBegin(GL_QUADS);
 255    glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f( 2.5f,-2.5f, DEPTH);
 256    glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f( 2.5f, 2.5f, DEPTH);
 257    glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 2.5f, 2.5f,-DEPTH);
 258    glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 2.5f,-2.5f,-DEPTH);
 259    glEnd();
 260
 261    /* Left */
 262    glBegin(GL_QUADS);
 263    glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-2.5f,-2.5f, DEPTH);
 264    glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-2.5f, 2.5f, DEPTH);
 265    glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f(-2.5f, 2.5f,-DEPTH);
 266    glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f(-2.5f,-2.5f,-DEPTH);
 267    glEnd();
 268 #endif
 269
 270    glutSwapBuffers();
 271 }
 272
 273
 274 static void Reshape( int width, int height )
 275 {
 276    glViewport(0, 0, width, height);
 277    glMatrixMode(GL_PROJECTION);
 278    glLoadIdentity();
 279    gluPerspective(45.0f, (GLfloat)(width)/(GLfloat)(height), 0.1f, 100.0f);
 280    glMatrixMode(GL_MODELVIEW);
 281    glLoadIdentity();
 282 }
 283
 284
 285 static void Key( unsigned char key, int x, int y )
 286 {
 287    (void) x;
 288    (void) y;
 289    switch (key) {
 290       case 'f':
 291          fogMode = SetFogMode(fogMode + 1);
 292          break;
 293       case '+':
 294          if (fogDensity < 1.0) {
 295             fogDensity += 0.05;
 296          }
 297          SetFogMode(fogMode);
 298          break;
 299       case '-':
 300          if (fogDensity > 0.0) {
 301             fogDensity -= 0.05;
 302          }
 303          SetFogMode(fogMode);
 304          break;
 305       case 's':
 306          if (fogStart > 0.0) {
 307             fogStart -= 1.0;
 308          }
 309          SetFogMode(fogMode);
 310          break;
 311       case 'S':
 312          if (fogStart < fogEnd) {
 313             fogStart += 1.0;
 314          }
 315          SetFogMode(fogMode);
 316          break;
 317       case 'e':
 318          if (fogEnd > fogStart) {
 319             fogEnd -= 1.0;
 320          }
 321          SetFogMode(fogMode);
 322          break;
 323       case 'E':
 324          if (fogEnd < 100.0) {
 325             fogEnd += 1.0;
 326          }
 327          SetFogMode(fogMode);
 328          break;
 329       case 'c':
 330          fogCoord = SetFogCoord(fogCoord ^ GL_TRUE);
 331          break;
 332       case 27:
 333          exit(0);
 334          break;
 335    }
 336    glutPostRedisplay();
 337 }
 338
 339
 340 static void SpecialKey( int key, int x, int y )
 341 {
 342    (void) x;
 343    (void) y;
 344    switch (key) {
 345       case GLUT_KEY_UP:
 346          if (camz < (DEPTH - 1.0)) {
 347             camz += 1.0f;
 348          }
 349          break;
 350       case GLUT_KEY_DOWN:
 351          if (camz > -19.0) {
 352             camz -= 1.0f;
 353          }
 354          break;
 355    }
 356    glutPostRedisplay();
 357 }
 358
 359
 360 static void Init( void )
 361 {
 362    have_fog_coord = glutExtensionSupported("GL_EXT_fog_coord");
 363
 364    if (BuildTexture(TEXTURE_FILE, texture) == -1) {
 365       exit(1);
 366    }
 367
 368    glEnable(GL_TEXTURE_2D);
 369    glClearColor(0.0f, 0.0f, 0.0f, 0.5f);
 370    glClearDepth(1.0f);
 371    glDepthFunc(GL_LEQUAL);
 372    glEnable(GL_DEPTH_TEST);
 373    glShadeModel(GL_SMOOTH);
 374    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
 375
 376    glFogfv(GL_FOG_COLOR, fogColor);
 377    glHint(GL_FOG_HINT, GL_NICEST);
 378    fogCoord = SetFogCoord(GL_TRUE); /* try to enable fog_coord */
 379    fogMode = SetFogMode(2);         /* GL_EXP */
 380
 381    camz = -19.0f;
 382
 383 #if ARRAYS
 384    glEnableClientState(GL_VERTEX_ARRAY);
 385    glVertexPointer(3, GL_FLOAT, 0, vertex_pointer);
 386
 387    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
 388    glTexCoordPointer(2, GL_FLOAT, 0, texcoord_pointer);
 389
 390    if (have_fog_coord) {
 391       glFogCoordPointer_ext = (GLFOGCOORDPOINTEREXTPROC)glutGetProcAddress("glFogCoordPointerEXT");
 392       glEnableClientState(GL_FOG_COORDINATE_ARRAY_EXT);
 393       glFogCoordPointer_ext(GL_FLOAT, 0, fogcoord_pointer);
 394    }
 395 #endif
 396 }
 397
 398
 399 int main( int argc, char *argv[] )
 400 {
 401    glutInit( &argc, argv );
 402    glutInitWindowPosition( 0, 0 );
 403    glutInitWindowSize( 640, 480 );
 404    glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
 405    glutCreateWindow(argv[0]);
 406    glutReshapeFunc( Reshape );
 407    glutKeyboardFunc( Key );
 408    glutSpecialFunc( SpecialKey );
 409    glutDisplayFunc( Display );
 410    Init();
 411    glutMainLoop();
 412    return 0;
 413 }