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.h"
  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 #if !defined(GLAPIENTRYP)
  27 #    define GLAPIENTRYP *
  28 #endif
  29
  30 typedef void (GLAPIENTRYP GLFOGCOORDFEXTPROC) (GLfloat f);
  31 typedef void (GLAPIENTRYP GLFOGCOORDPOINTEREXTPROC) (GLenum, GLsizei, const GLvoid *);
  32
  33 static GLFOGCOORDFEXTPROC glFogCoordf_ext;
  34 #if ARRAYS
  35 static GLFOGCOORDPOINTEREXTPROC glFogCoordPointer_ext;
  36 #endif
  37 static GLboolean have_fog_coord;
  38
  39 static GLfloat camz;
  40 static GLuint texture[1];
  41
  42 static GLint fogMode;
  43 static GLboolean fogCoord;
  44 static GLfloat fogDensity = 0.75;
  45 static GLfloat fogStart = 1.0, fogEnd = 40.0;
  46 static GLfloat fogColor[4] = {0.6f, 0.3f, 0.0f, 1.0f};
  47
  48
  49 static void APIENTRY glFogCoordf_nop (GLfloat f)
  50 {
  51    (void)f;
  52 }
  53
  54
  55 static int BuildTexture (const char *filename, GLuint texid[])
  56 {
  57    GLubyte *tex_data;
  58    GLenum tex_format;
  59    GLint tex_width, tex_height;
  60
  61    tex_data = LoadRGBImage(filename, &tex_width, &tex_height, &tex_format);
  62    if (tex_data == NULL) {
  63       return -1;
  64    }
  65
  66    {
  67       GLint tex_max;
  68       glGetIntegerv(GL_MAX_TEXTURE_SIZE, &tex_max);
  69       if ((tex_width > tex_max) || (tex_height > tex_max)) {
  70          return -1;
  71       }
  72    }
  73
  74    glGenTextures(1, texid);
  75
  76    glBindTexture(GL_TEXTURE_2D, texid[0]);
  77    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  78    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  79
  80    glTexImage2D(GL_TEXTURE_2D, 0, tex_format, tex_width, tex_height, 0,
  81                 tex_format, GL_UNSIGNED_BYTE, tex_data);
  82
  83    return 0;
  84 }
  85
  86
  87 static int SetFogMode (GLint fogMode)
  88 {
  89    fogMode &= 3;
  90    switch (fogMode) {
  91    case 0:
  92       glDisable(GL_FOG);
  93 #if VERBOSE
  94       printf("fog(disable)\n");
  95 #endif
  96       break;
  97    case 1:
  98       glEnable(GL_FOG);
  99       glFogi(GL_FOG_MODE, GL_LINEAR);
 100       glFogf(GL_FOG_START, fogStart);
 101       glFogf(GL_FOG_END, fogEnd);
 102 #if VERBOSE
 103       printf("fog(GL_LINEAR, %.2f, %.2f)\n", fogStart, fogEnd);
 104 #endif
 105       break;
 106    case 2:
 107       glEnable(GL_FOG);
 108       glFogi(GL_FOG_MODE, GL_EXP);
 109       glFogf(GL_FOG_DENSITY, fogDensity);
 110 #if VERBOSE
 111       printf("fog(GL_EXP, %.2f)\n", fogDensity);
 112 #endif
 113       break;
 114    case 3:
 115       glEnable(GL_FOG);
 116       glFogi(GL_FOG_MODE, GL_EXP2);
 117       glFogf(GL_FOG_DENSITY, fogDensity);
 118 #if VERBOSE
 119       printf("fog(GL_EXP2, %.2f)\n", fogDensity);
 120 #endif
 121       break;
 122    }
 123    return fogMode;
 124 }
 125
 126
 127 static GLboolean SetFogCoord (GLboolean fogCoord)
 128 {
 129    glFogCoordf_ext = glFogCoordf_nop;
 130
 131    if (!have_fog_coord) {
 132 #if VERBOSE
 133       printf("fog(GL_FRAGMENT_DEPTH_EXT)%s\n", fogCoord ? " EXT_fog_coord not available!" : "");
 134 #endif
 135       return GL_FALSE;
 136    }
 137
 138    if (fogCoord) {
 139       glFogCoordf_ext = (GLFOGCOORDFEXTPROC)glutGetProcAddress("glFogCoordfEXT");
 140       glFogi(GL_FOG_COORDINATE_SOURCE_EXT, GL_FOG_COORDINATE_EXT);
 141 #if VERBOSE
 142       printf("fog(GL_FOG_COORDINATE_EXT)\n");
 143 #endif
 144    } else {
 145       glFogi(GL_FOG_COORDINATE_SOURCE_EXT, GL_FRAGMENT_DEPTH_EXT);
 146 #if VERBOSE
 147       printf("fog(GL_FRAGMENT_DEPTH_EXT)\n");
 148 #endif
 149    }
 150    return fogCoord;
 151 }
 152
 153
 154 #if ARRAYS
 155 /* could reuse vertices */
 156 static GLuint vertex_index[] = {
 157    /* Back */
 158    0, 1, 2, 3,
 159
 160    /* Floor */
 161    4, 5, 6, 7,
 162
 163    /* Roof */
 164    8, 9, 10, 11,
 165
 166    /* Right */
 167    12, 13, 14, 15,
 168
 169    /* Left */
 170    16, 17, 18, 19
 171 };
 172
 173 static GLfloat vertex_pointer[][3] = {
 174    /* Back */
 175    {-2.5f,-2.5f,-DEPTH}, { 2.5f,-2.5f,-DEPTH}, { 2.5f, 2.5f,-DEPTH}, {-2.5f, 2.5f,-DEPTH},
 176
 177    /* Floor */
 178    {-2.5f,-2.5f,-DEPTH}, { 2.5f,-2.5f,-DEPTH}, { 2.5f,-2.5f, DEPTH}, {-2.5f,-2.5f, DEPTH},
 179
 180    /* Roof */
 181    {-2.5f, 2.5f,-DEPTH}, { 2.5f, 2.5f,-DEPTH}, { 2.5f, 2.5f, DEPTH}, {-2.5f, 2.5f, DEPTH},
 182
 183    /* Right */
 184    { 2.5f,-2.5f, DEPTH}, { 2.5f, 2.5f, DEPTH}, { 2.5f, 2.5f,-DEPTH}, { 2.5f,-2.5f,-DEPTH},
 185
 186    /* Left */
 187    {-2.5f,-2.5f, DEPTH}, {-2.5f, 2.5f, DEPTH}, {-2.5f, 2.5f,-DEPTH}, {-2.5f,-2.5f,-DEPTH}
 188 };
 189
 190 static GLfloat texcoord_pointer[][2] = {
 191    /* Back */
 192    {0.0f, 0.0f}, {1.0f, 0.0f}, {1.0f, 1.0f}, {0.0f, 1.0f},
 193
 194    /* Floor */
 195    {0.0f, 0.0f}, {1.0f, 0.0f}, {1.0f, 1.0f}, {0.0f, 1.0f},
 196
 197    /* Roof */
 198    {0.0f, 0.0f}, {1.0f, 0.0f}, {1.0f, 1.0f}, {0.0f, 1.0f},
 199
 200    /* Right */
 201    {0.0f, 0.0f}, {0.0f, 1.0f}, {1.0f, 1.0f}, {1.0f, 0.0f},
 202
 203    /* Left */
 204    {0.0f, 0.0f}, {0.0f, 1.0f}, {1.0f, 1.0f}, {1.0f, 0.0f}
 205 };
 206
 207 static GLfloat fogcoord_pointer[][1] = {
 208    /* Back */
 209    {1.0f}, {1.0f}, {1.0f}, {1.0f},
 210
 211    /* Floor */
 212    {1.0f}, {1.0f}, {0.0f}, {0.0f},
 213
 214    /* Roof */
 215    {1.0f}, {1.0f}, {0.0f}, {0.0f},
 216
 217    /* Right */
 218    {0.0f}, {0.0f}, {1.0f}, {1.0f},
 219
 220    /* Left */
 221    {0.0f}, {0.0f}, {1.0f}, {1.0f}
 222 };
 223 #endif
 224
 225
 226 static void Display( void )
 227 {
 228    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 229    glLoadIdentity ();
 230
 231    glTranslatef(0.0f, 0.0f, camz);
 232
 233 #if ARRAYS
 234    glDrawElements(GL_QUADS, sizeof(vertex_index) / sizeof(vertex_index[0]), GL_UNSIGNED_INT, vertex_index);
 235 #else
 236    /* Back */
 237    glBegin(GL_QUADS);
 238    glFogCoordf_ext(1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-2.5f,-2.5f,-DEPTH);
 239    glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 2.5f,-2.5f,-DEPTH);
 240    glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 2.5f, 2.5f,-DEPTH);
 241    glFogCoordf_ext(1.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-2.5f, 2.5f,-DEPTH);
 242    glEnd();
 243
 244    /* Floor */
 245    glBegin(GL_QUADS);
 246    glFogCoordf_ext(1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-2.5f,-2.5f,-DEPTH);
 247    glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 2.5f,-2.5f,-DEPTH);
 248    glFogCoordf_ext(0.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 2.5f,-2.5f, DEPTH);
 249    glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-2.5f,-2.5f, DEPTH);
 250    glEnd();
 251
 252    /* Roof */
 253    glBegin(GL_QUADS);
 254    glFogCoordf_ext(1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-2.5f, 2.5f,-DEPTH);
 255    glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 2.5f, 2.5f,-DEPTH);
 256    glFogCoordf_ext(0.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 2.5f, 2.5f, DEPTH);
 257    glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-2.5f, 2.5f, DEPTH);
 258    glEnd();
 259
 260    /* Right */
 261    glBegin(GL_QUADS);
 262    glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f( 2.5f,-2.5f, DEPTH);
 263    glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f( 2.5f, 2.5f, DEPTH);
 264    glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 2.5f, 2.5f,-DEPTH);
 265    glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 2.5f,-2.5f,-DEPTH);
 266    glEnd();
 267
 268    /* Left */
 269    glBegin(GL_QUADS);
 270    glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-2.5f,-2.5f, DEPTH);
 271    glFogCoordf_ext(0.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-2.5f, 2.5f, DEPTH);
 272    glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f(-2.5f, 2.5f,-DEPTH);
 273    glFogCoordf_ext(1.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f(-2.5f,-2.5f,-DEPTH);
 274    glEnd();
 275 #endif
 276
 277    glutSwapBuffers();
 278 }
 279
 280
 281 static void Reshape( int width, int height )
 282 {
 283    glViewport(0, 0, width, height);
 284    glMatrixMode(GL_PROJECTION);
 285    glLoadIdentity();
 286    gluPerspective(45.0f, (GLfloat)(width)/(GLfloat)(height), 0.1f, 100.0f);
 287    glMatrixMode(GL_MODELVIEW);
 288    glLoadIdentity();
 289 }
 290
 291
 292 static void Key( unsigned char key, int x, int y )
 293 {
 294    (void) x;
 295    (void) y;
 296    switch (key) {
 297       case 'f':
 298          fogMode = SetFogMode(fogMode + 1);
 299          break;
 300       case '+':
 301          if (fogDensity < 1.0) {
 302             fogDensity += 0.05;
 303          }
 304          SetFogMode(fogMode);
 305          break;
 306       case '-':
 307          if (fogDensity > 0.0) {
 308             fogDensity -= 0.05;
 309          }
 310          SetFogMode(fogMode);
 311          break;
 312       case 's':
 313          if (fogStart > 0.0) {
 314             fogStart -= 1.0;
 315          }
 316          SetFogMode(fogMode);
 317          break;
 318       case 'S':
 319          if (fogStart < fogEnd) {
 320             fogStart += 1.0;
 321          }
 322          SetFogMode(fogMode);
 323          break;
 324       case 'e':
 325          if (fogEnd > fogStart) {
 326             fogEnd -= 1.0;
 327          }
 328          SetFogMode(fogMode);
 329          break;
 330       case 'E':
 331          if (fogEnd < 100.0) {
 332             fogEnd += 1.0;
 333          }
 334          SetFogMode(fogMode);
 335          break;
 336       case 'c':
 337          fogCoord = SetFogCoord(fogCoord ^ GL_TRUE);
 338          break;
 339       case 27:
 340          exit(0);
 341          break;
 342    }
 343    glutPostRedisplay();
 344 }
 345
 346
 347 static void SpecialKey( int key, int x, int y )
 348 {
 349    (void) x;
 350    (void) y;
 351    switch (key) {
 352       case GLUT_KEY_UP:
 353          if (camz < (DEPTH - 1.0)) {
 354             camz += 1.0f;
 355          }
 356          break;
 357       case GLUT_KEY_DOWN:
 358          if (camz > -19.0) {
 359             camz -= 1.0f;
 360          }
 361          break;
 362    }
 363    glutPostRedisplay();
 364 }
 365
 366
 367 static void Init( void )
 368 {
 369    have_fog_coord = glutExtensionSupported("GL_EXT_fog_coord");
 370
 371    if (BuildTexture(TEXTURE_FILE, texture) == -1) {
 372       exit(1);
 373    }
 374
 375    glEnable(GL_TEXTURE_2D);
 376    glClearColor(0.0f, 0.0f, 0.0f, 0.5f);
 377    glClearDepth(1.0f);
 378    glDepthFunc(GL_LEQUAL);
 379    glEnable(GL_DEPTH_TEST);
 380    glShadeModel(GL_SMOOTH);
 381    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
 382
 383    glFogfv(GL_FOG_COLOR, fogColor);
 384    glHint(GL_FOG_HINT, GL_NICEST);
 385    fogCoord = SetFogCoord(GL_TRUE); /* try to enable fog_coord */
 386    fogMode = SetFogMode(2);         /* GL_EXP */
 387
 388    camz = -19.0f;
 389
 390 #if ARRAYS
 391    glEnableClientState(GL_VERTEX_ARRAY);
 392    glVertexPointer(3, GL_FLOAT, 0, vertex_pointer);
 393
 394    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
 395    glTexCoordPointer(2, GL_FLOAT, 0, texcoord_pointer);
 396
 397    if (have_fog_coord) {
 398       glFogCoordPointer_ext = (GLFOGCOORDPOINTEREXTPROC)glutGetProcAddress("glFogCoordPointerEXT");
 399       glEnableClientState(GL_FOG_COORDINATE_ARRAY_EXT);
 400       glFogCoordPointer_ext(GL_FLOAT, 0, fogcoord_pointer);
 401    }
 402 #endif
 403 }
 404
 405
 406 int main( int argc, char *argv[] )
 407 {
 408    glutInit( &argc, argv );
 409    glutInitWindowPosition( 0, 0 );
 410    glutInitWindowSize( 640, 480 );
 411    glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
 412    glutCreateWindow(argv[0]);
 413    glutReshapeFunc( Reshape );
 414    glutKeyboardFunc( Key );
 415    glutSpecialFunc( SpecialKey );
 416    glutDisplayFunc( Display );
 417    Init();
 418    glutMainLoop();
 419    return 0;
 420 }