summaryrefslogtreecommitdiff
path: root/progs/demos/shadowtex.c
blob: 18aad47ed534e492b04f5affb3cb10d96890565f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
/*
 * Shadow demo using the GL_ARB_depth_texture, GL_ARB_shadow and
 * GL_ARB_shadow_ambient extensions (or the old SGIX extensions).
 *
 * Brian Paul
 * 19 Feb 2001
 *
 * Added GL_EXT_shadow_funcs support on 23 March 2002
 *
 * Copyright (C) 1999-2001  Brian Paul   All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */


#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glut.h>
#include "../util/showbuffer.c"

#if 0 /* change to 1 if you want to use the old SGIX extensions */
#undef GL_ARB_depth_texture
#undef GL_ARB_shadow
#undef GL_ARB_shadow_ambient
#endif


#define DEG_TO_RAD (3.14159 / 180.0)

static GLint WindowWidth = 450, WindowHeight = 300;
static GLfloat Xrot = 15, Yrot = 0, Zrot = 0;

static GLfloat Red[4] = {1, 0, 0, 1};
static GLfloat Green[4] = {0, 1, 0, 1};
static GLfloat Blue[4] = {0, 0, 1, 1};
static GLfloat Yellow[4] = {1, 1, 0, 1};

static GLfloat LightDist = 10;
static GLfloat LightLatitude = 45.0;
static GLfloat LightLongitude = 45.0;
static GLfloat LightPos[4];
static GLfloat SpotDir[3];
static GLfloat SpotAngle = 40.0 * DEG_TO_RAD;
static GLfloat ShadowNear = 4.0, ShadowFar = 24.0;
static GLint ShadowTexWidth = 256, ShadowTexHeight = 256;

static GLboolean LinearFilter = GL_FALSE;

static GLfloat Bias = -0.06;

static GLboolean Anim = GL_TRUE;

static GLboolean HaveEXTshadowFuncs = GL_FALSE;
static GLint Operator = 0;
static const GLenum OperatorFunc[8] = {
   GL_LEQUAL, GL_LESS, GL_GEQUAL, GL_GREATER,
   GL_EQUAL, GL_NOTEQUAL, GL_ALWAYS, GL_NEVER };
static const char *OperatorName[8] = {
   "GL_LEQUAL", "GL_LESS", "GL_GEQUAL", "GL_GREATER",
   "GL_EQUAL", "GL_NOTEQUAL", "GL_ALWAYS", "GL_NEVER" };


static GLuint DisplayMode;
#define SHOW_NORMAL         0
#define SHOW_DEPTH_IMAGE    1
#define SHOW_DEPTH_MAPPING  2
#define SHOW_DISTANCE       3



static void
DrawScene(void)
{
   GLfloat k = 6;
   /* sphere */
   glPushMatrix();
   glTranslatef(1.6, 2.2, 2.7);
   glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, Green);
   glColor4fv(Green);
   glutSolidSphere(1.5, 15, 15);
   glPopMatrix();
   /* dodecahedron */
   glPushMatrix();
   glTranslatef(-2.0, 1.2, 2.1);
   glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, Red);
   glColor4fv(Red);
   glutSolidDodecahedron();
   glPopMatrix();
   /* icosahedron */
   glPushMatrix();
   glTranslatef(-0.6, 1.3, -0.5);
   glScalef(1.5, 1.5, 1.5);
   glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, Yellow);
   glColor4fv(Red);
   glutSolidIcosahedron();
   glPopMatrix();
   /* a plane */
   glPushMatrix();
   glTranslatef(0, -1.1, 0);
   glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, Blue);
   glColor4fv(Blue);
   glNormal3f(0, 1, 0);
   glBegin(GL_POLYGON);
   glVertex3f(-k, 0, -k);
   glVertex3f( k, 0, -k);
   glVertex3f( k, 0,  k);
   glVertex3f(-k, 0,  k);
   glEnd();
   glPopMatrix();
}


/*
 * Load the GL_TEXTURE matrix with the projection from the light
 * source's point of view.
 */
static void
MakeShadowMatrix(const GLfloat lightPos[4], const GLfloat spotDir[3],
                 GLfloat spotAngle, GLfloat shadowNear, GLfloat shadowFar)
{
   GLfloat d;
   
   glMatrixMode(GL_TEXTURE);
   glLoadIdentity();
   glTranslatef(0.5, 0.5, 0.5 + Bias);
   glScalef(0.5, 0.5, 0.5);
   d = shadowNear * tan(spotAngle);
   glFrustum(-d, d, -d, d, shadowNear, shadowFar);
   gluLookAt(lightPos[0], lightPos[1], lightPos[2],
             lightPos[0] + spotDir[0],
             lightPos[1] + spotDir[1],
             lightPos[2] + spotDir[2],
             0, 1, 0);
   glMatrixMode(GL_MODELVIEW);
}


static void
EnableIdentityTexgen(void)
{
   /* texgen so that texcoord = vertex coord */
   static GLfloat sPlane[4] = { 1, 0, 0, 0 };
   static GLfloat tPlane[4] = { 0, 1, 0, 0 };
   static GLfloat rPlane[4] = { 0, 0, 1, 0 };
   static GLfloat qPlane[4] = { 0, 0, 0, 1 };

   glTexGenfv(GL_S, GL_EYE_PLANE, sPlane);
   glTexGenfv(GL_T, GL_EYE_PLANE, tPlane);
   glTexGenfv(GL_R, GL_EYE_PLANE, rPlane);
   glTexGenfv(GL_Q, GL_EYE_PLANE, qPlane);
   glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
   glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
   glTexGeni(GL_R, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
   glTexGeni(GL_Q, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);

   glEnable(GL_TEXTURE_GEN_S);
   glEnable(GL_TEXTURE_GEN_T);
   glEnable(GL_TEXTURE_GEN_R);
   glEnable(GL_TEXTURE_GEN_Q);
}


/*
 * Setup 1-D texgen so that the distance from the light source, between
 * the near and far planes maps to s=0 and s=1.  When we draw the scene,
 * the grayness will indicate the fragment's distance from the light
 * source.
 */
static void
EnableDistanceTexgen(const GLfloat lightPos[4], const GLfloat lightDir[3],
                     GLfloat lightNear, GLfloat lightFar)
{
   GLfloat m, d;
   GLfloat sPlane[4];
   GLfloat nearPoint[3];

   m = sqrt(lightDir[0] * lightDir[0] +
            lightDir[1] * lightDir[1] +
            lightDir[2] * lightDir[2]);

   d = lightFar - lightNear;

   /* nearPoint = point on light direction vector which intersects the
    * near plane of the light frustum.
    */
   nearPoint[0] = LightPos[0] + lightDir[0] / m * lightNear;
   nearPoint[1] = LightPos[1] + lightDir[1] / m * lightNear;
   nearPoint[2] = LightPos[2] + lightDir[2] / m * lightNear;

   sPlane[0] = lightDir[0] / d / m;
   sPlane[1] = lightDir[1] / d / m;
   sPlane[2] = lightDir[2] / d / m;
   sPlane[3] = -(sPlane[0] * nearPoint[0]
               + sPlane[1] * nearPoint[1]
               + sPlane[2] * nearPoint[2]);

   glTexGenfv(GL_S, GL_EYE_PLANE, sPlane);
   glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
   glEnable(GL_TEXTURE_GEN_S);
}


static void
DisableTexgen(void)
{
   glDisable(GL_TEXTURE_GEN_S);
   glDisable(GL_TEXTURE_GEN_T);
   glDisable(GL_TEXTURE_GEN_R);
   glDisable(GL_TEXTURE_GEN_Q);
}


static void
ComputeLightPos(GLfloat dist, GLfloat latitude, GLfloat longitude,
                GLfloat pos[4], GLfloat dir[3])
{

   pos[0] = dist * sin(longitude * DEG_TO_RAD);
   pos[1] = dist * sin(latitude * DEG_TO_RAD);
   pos[2] = dist * cos(latitude * DEG_TO_RAD) * cos(longitude * DEG_TO_RAD);
   pos[3] = 1;
   dir[0] = -pos[0];
   dir[1] = -pos[1];
   dir[2] = -pos[2];
}


static void
Display(void)
{
   GLfloat ar = (GLfloat) WindowWidth / (GLfloat) WindowHeight;
   GLfloat d;
   GLenum error;

   ComputeLightPos(LightDist, LightLatitude, LightLongitude,
                   LightPos, SpotDir);
   /*
    * Step 1: render scene from point of view of the light source
    */
   /* compute frustum to enclose spot light cone */
   d = ShadowNear * tan(SpotAngle);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glFrustum(-d, d, -d, d, ShadowNear, ShadowFar);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
   gluLookAt(LightPos[0], LightPos[1], LightPos[2], /* from */
             0, 0, 0, /* target */
             0, 1, 0); /* up */

   glViewport(0, 0, ShadowTexWidth, ShadowTexHeight);
   glClear(GL_DEPTH_BUFFER_BIT);
   DrawScene();

   /*
    * Step 2: copy depth buffer into texture map
    */
   if (DisplayMode == SHOW_DEPTH_MAPPING) {
      /* load depth image as gray-scale luminance texture */
      GLfloat *depth = (GLfloat *) malloc(ShadowTexWidth * ShadowTexHeight
                                          * sizeof(GLfloat));
      if (depth) {
         glReadPixels(0, 0, ShadowTexWidth, ShadowTexHeight,
                      GL_DEPTH_COMPONENT, GL_FLOAT, depth);
         glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE,
                      ShadowTexWidth, ShadowTexHeight, 0,
                      GL_LUMINANCE, GL_FLOAT, depth);
         free(depth);
      }
   }
   else {
      /* The normal shadow case */
      glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT,
                       0, 0, ShadowTexWidth, ShadowTexHeight, 0);
   }

   /*
    * Step 3: render scene from point of view of the camera
    */
   glViewport(0, 0, WindowWidth, WindowHeight);
   if (DisplayMode == SHOW_DEPTH_IMAGE) {
      ShowDepthBuffer(WindowWidth, WindowHeight, 0, 1);
   }
   else {
      glMatrixMode(GL_PROJECTION);
      glLoadIdentity();
      glFrustum(-ar, ar, -1.0, 1.0, 4.0, 50.0);
      glMatrixMode(GL_MODELVIEW);
      glLoadIdentity();
      glTranslatef(0.0, 0.0, -22.0);
      glRotatef(Xrot, 1, 0, 0);
      glRotatef(Yrot, 0, 1, 0);
      glRotatef(Zrot, 0, 0, 1);
      glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
      glLightfv(GL_LIGHT0, GL_POSITION, LightPos);
      if (LinearFilter) {
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
      }
      else {
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
      }
      if (DisplayMode == SHOW_DEPTH_MAPPING) {
#if defined(GL_ARB_shadow)
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE_ARB, GL_NONE);
#elif defined(GL_SGIX_shadow)
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_SGIX, GL_FALSE);
#endif
         glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
         glEnable(GL_TEXTURE_2D);
         MakeShadowMatrix(LightPos, SpotDir, SpotAngle, ShadowNear, ShadowFar);
         EnableIdentityTexgen();
      }
      else if (DisplayMode == SHOW_DISTANCE) {
         glMatrixMode(GL_TEXTURE);
         glLoadIdentity();
         glMatrixMode(GL_MODELVIEW);
         EnableDistanceTexgen(LightPos, SpotDir, ShadowNear+Bias, ShadowFar);
         glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
         glEnable(GL_TEXTURE_1D);
      }
      else {
         assert(DisplayMode == SHOW_NORMAL);
#if defined(GL_ARB_shadow)
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE_ARB,
                         GL_COMPARE_R_TO_TEXTURE_ARB);
#elif defined(GL_SGIX_shadow)
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_SGIX, GL_TRUE);
#endif
         glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
         glEnable(GL_TEXTURE_2D);
         MakeShadowMatrix(LightPos, SpotDir, SpotAngle, ShadowNear, ShadowFar);
         EnableIdentityTexgen();
      }
      DrawScene();
      DisableTexgen();
      glDisable(GL_TEXTURE_1D);
      glDisable(GL_TEXTURE_2D);
   }

   glutSwapBuffers();

   error = glGetError();
   if (error) {
      printf("GL Error: %s\n", (char *) gluErrorString(error));
   }
}


static void
Reshape(int width, int height)
{
   WindowWidth = width;
   WindowHeight = height;
   if (width >= 512 && height >= 512) {
      ShadowTexWidth = ShadowTexHeight = 512;
   }
   else if (width >= 256 && height >= 256) {
      ShadowTexWidth = ShadowTexHeight = 256;
   }
   else {
      ShadowTexWidth = ShadowTexHeight = 128;
   }
   printf("Using %d x %d depth texture\n", ShadowTexWidth, ShadowTexHeight);
}


static void
Idle(void)
{
   Yrot += 5.0;
   /*LightLongitude -= 5.0;*/
   glutPostRedisplay();
}


static void
Key(unsigned char key, int x, int y)
{
   const GLfloat step = 3.0;
   (void) x;
   (void) y;
   switch (key) {
      case 'a':
         Anim = !Anim;
         if (Anim)
            glutIdleFunc(Idle);
         else
            glutIdleFunc(NULL);
         break;
      case 'b':
         Bias -= 0.01;
         printf("Bias %g\n", Bias);
         break;
      case 'B':
         Bias += 0.01;
         printf("Bias %g\n", Bias);
         break;
      case 'd':
         DisplayMode = SHOW_DISTANCE;
         break;
      case 'f':
         LinearFilter = !LinearFilter;
         printf("%s filtering\n", LinearFilter ? "Bilinear" : "Nearest");
         break;
      case 'i':
         DisplayMode = SHOW_DEPTH_IMAGE;
         break;
      case 'm':
         DisplayMode = SHOW_DEPTH_MAPPING;
         break;
      case 'n':
      case ' ':
         DisplayMode = SHOW_NORMAL;
         break;
      case 'o':
         if (HaveEXTshadowFuncs) {
            Operator++;
            if (Operator >= 8)
               Operator = 0;
            printf("Operator: %s\n", OperatorName[Operator]);
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC_ARB,
                            OperatorFunc[Operator]);
         }
         break;
      case 'z':
         Zrot -= step;
         break;
      case 'Z':
         Zrot += step;
         break;
      case 27:
         exit(0);
         break;
   }
   glutPostRedisplay();
}


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


static void
Init(void)
{
#if defined(GL_ARB_depth_texture) && defined(GL_ARB_shadow)
   if (!glutExtensionSupported("GL_ARB_depth_texture") ||
       !glutExtensionSupported("GL_ARB_shadow")) {
      printf("Sorry, this demo requires the GL_ARB_depth_texture and GL_ARB_shadow extensions\n");
      exit(1);
   }
   printf("Using GL_ARB_depth_texture and GL_ARB_shadow\n");
#elif defined(GL_SGIX_depth_texture) && defined(GL_SGIX_shadow)
   if (!glutExtensionSupported("GL_SGIX_depth_texture") ||
       !glutExtensionSupported("GL_SGIX_shadow")) {
      printf("Sorry, this demo requires the GL_SGIX_depth_texture and GL_SGIX_shadow extensions\n");
      exit(1);
   }
   printf("Using GL_SGIX_depth_texture and GL_SGIX_shadow\n");
#endif
   HaveEXTshadowFuncs = glutExtensionSupported("GL_EXT_shadow_funcs");

   glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_WRAP_S, GL_CLAMP);
   glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
   glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
   glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_WRAP_T, GL_CLAMP);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
#if defined(GL_ARB_shadow)
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE_ARB,
                   GL_COMPARE_R_TO_TEXTURE_ARB);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC_ARB, GL_LEQUAL);
#elif defined(GL_SGIX_shadow)
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_OPERATOR_SGIX,
                   GL_TEXTURE_LEQUAL_R_SGIX);
#endif

#if defined(GL_ARB_shadow_ambient)
   if (glutExtensionSupported("GL_ARB_shadow_ambient")) {
      glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FAIL_VALUE_ARB, 0.3);
      printf("and GL_ARB_shadow_ambient\n");
   }
#elif defined(GL_SGIX_shadow_ambient)
   if (glutExtensionSupported("GL_SGIX_shadow_ambient")) {
      glTexParameterf(GL_TEXTURE_2D, GL_SHADOW_AMBIENT_SGIX, 0.3);
      printf("and GL_SGIX_shadow_ambient\n");
   }
#endif

   /* setup 1-D grayscale texture image for SHOW_DISTANCE mode */
   {
      GLuint i;
      GLubyte image[256];
      for (i = 0; i < 256; i++)
         image[i] = i;
      glTexImage1D(GL_TEXTURE_1D, 0, GL_LUMINANCE,
                   256, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, image);
   }

   glEnable(GL_DEPTH_TEST);
   glEnable(GL_LIGHTING);
   glEnable(GL_LIGHT0);
}


static void
PrintHelp(void)
{
   printf("Keys:\n");
   printf("  a = toggle animation\n");
   printf("  i = show depth texture image\n");
   printf("  m = show depth texture mapping\n");
   printf("  d = show fragment distance from light source\n");
   printf("  n = show normal, shadowed image\n");
   printf("  f = toggle nearest/bilinear texture filtering\n");
   printf("  b/B = decrease/increase shadow map Z bias\n");
   printf("  cursor keys = rotate scene\n");
   printf("  <shift> + cursor keys = rotate light source\n");
   if (HaveEXTshadowFuncs)
      printf("  o = cycle through comparison modes\n");
}


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