summaryrefslogtreecommitdiffstats
path: root/progs/demos/dinoshade.c
blob: 451da2ec8955d3d38cdb36c6c37aa6011c3fc6a3 (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
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912

/* Copyright (c) Mark J. Kilgard, 1994, 1997.  */

/* This program is freely distributable without licensing fees 
   and is provided without guarantee or warrantee expressed or 
   implied. This program is -not- in the public domain. */

/* Example for PC game developers to show how to *combine* texturing,
   reflections, and projected shadows all in real-time with OpenGL.
   Robust reflections use stenciling.  Robust projected shadows
   use both stenciling and polygon offset.  PC game programmers
   should realize that neither stenciling nor polygon offset are 
   supported by Direct3D, so these real-time rendering algorithms
   are only really viable with OpenGL. 
   
   The program has modes for disabling the stenciling and polygon
   offset uses.  It is worth running this example with these features
   toggled off so you can see the sort of artifacts that result.
   
   Notice that the floor texturing, reflections, and shadowing
   all co-exist properly. */

/* When you run this program:  Left mouse button controls the
   view.  Middle mouse button controls light position (left &
   right rotates light around dino; up & down moves light
   position up and down).  Right mouse button pops up menu. */

/* Check out the comments in the "redraw" routine to see how the
   reflection blending and surface stenciling is done.  You can
   also see in "redraw" how the projected shadows are rendered,
   including the use of stenciling and polygon offset. */

/* This program is derived from glutdino.c */

/* Compile: cc -o dinoshade dinoshade.c -lglut -lGLU -lGL -lXmu -lXext -lX11 -lm */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>       /* for cos(), sin(), and sqrt() */
#include <stddef.h>	/* for ptrdiff_t, referenced by GL.h when GL_GLEXT_LEGACY defined */
#ifdef _WIN32
#include <windows.h>
#endif
#define GL_GLEXT_LEGACY
#include <GL/glew.h>    /* OpenGL Utility Toolkit header */
#include <GL/glut.h>    /* OpenGL Utility Toolkit header */

/* Some <math.h> files do not define M_PI... */
#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

/* Variable controlling various rendering modes. */
static int stencilReflection = 1, stencilShadow = 1, offsetShadow = 1;
static int renderShadow = 1, renderDinosaur = 1, renderReflection = 1;
static int linearFiltering = 0, useMipmaps = 0, useTexture = 1;
static int reportSpeed = 0;
static int animation = 1;
static GLboolean lightSwitch = GL_TRUE;
static int directionalLight = 1;
static int forceExtension = 0;

/* Time varying or user-controled variables. */
static float jump = 0.0;
static float lightAngle = 0.0, lightHeight = 20;
GLfloat angle = -150;   /* in degrees */
GLfloat angle2 = 30;   /* in degrees */

int moving, startx, starty;
int lightMoving = 0, lightStartX, lightStartY;

enum {
  MISSING, EXTENSION, ONE_DOT_ONE
};
int polygonOffsetVersion;

static GLdouble bodyWidth = 3.0;
/* *INDENT-OFF* */
static GLfloat body[][2] = { {0, 3}, {1, 1}, {5, 1}, {8, 4}, {10, 4}, {11, 5},
  {11, 11.5}, {13, 12}, {13, 13}, {10, 13.5}, {13, 14}, {13, 15}, {11, 16},
  {8, 16}, {7, 15}, {7, 13}, {8, 12}, {7, 11}, {6, 6}, {4, 3}, {3, 2},
  {1, 2} };
static GLfloat arm[][2] = { {8, 10}, {9, 9}, {10, 9}, {13, 8}, {14, 9}, {16, 9},
  {15, 9.5}, {16, 10}, {15, 10}, {15.5, 11}, {14.5, 10}, {14, 11}, {14, 10},
  {13, 9}, {11, 11}, {9, 11} };
static GLfloat leg[][2] = { {8, 6}, {8, 4}, {9, 3}, {9, 2}, {8, 1}, {8, 0.5}, {9, 0},
  {12, 0}, {10, 1}, {10, 2}, {12, 4}, {11, 6}, {10, 7}, {9, 7} };
static GLfloat eye[][2] = { {8.75, 15}, {9, 14.7}, {9.6, 14.7}, {10.1, 15},
  {9.6, 15.25}, {9, 15.25} };
static GLfloat lightPosition[4];
static GLfloat lightColor[] = {0.8, 1.0, 0.8, 1.0}; /* green-tinted */
static GLfloat skinColor[] = {0.1, 1.0, 0.1, 1.0}, eyeColor[] = {1.0, 0.2, 0.2, 1.0};
/* *INDENT-ON* */

/* Nice floor texture tiling pattern. */
static char *circles[] = {
  "....xxxx........",
  "..xxxxxxxx......",
  ".xxxxxxxxxx.....",
  ".xxx....xxx.....",
  "xxx......xxx....",
  "xxx......xxx....",
  "xxx......xxx....",
  "xxx......xxx....",
  ".xxx....xxx.....",
  ".xxxxxxxxxx.....",
  "..xxxxxxxx......",
  "....xxxx........",
  "................",
  "................",
  "................",
  "................",
};

static void
makeFloorTexture(void)
{
  GLubyte floorTexture[16][16][3];
  GLubyte *loc;
  int s, t;

  /* Setup RGB image for the texture. */
  loc = (GLubyte*) floorTexture;
  for (t = 0; t < 16; t++) {
    for (s = 0; s < 16; s++) {
      if (circles[t][s] == 'x') {
	/* Nice green. */
        loc[0] = 0x1f;
        loc[1] = 0x8f;
        loc[2] = 0x1f;
      } else {
	/* Light gray. */
        loc[0] = 0xaa;
        loc[1] = 0xaa;
        loc[2] = 0xaa;
      }
      loc += 3;
    }
  }

  glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

  if (useMipmaps) {
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
      GL_LINEAR_MIPMAP_LINEAR);
    gluBuild2DMipmaps(GL_TEXTURE_2D, 3, 16, 16,
      GL_RGB, GL_UNSIGNED_BYTE, floorTexture);
  } else {
    if (linearFiltering) {
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    } else {
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    }
    glTexImage2D(GL_TEXTURE_2D, 0, 3, 16, 16, 0,
      GL_RGB, GL_UNSIGNED_BYTE, floorTexture);
  }
}

enum {
  X, Y, Z, W
};
enum {
  A, B, C, D
};

/* Create a matrix that will project the desired shadow. */
static void
shadowMatrix(GLfloat shadowMat[4][4],
  GLfloat groundplane[4],
  GLfloat lightpos[4])
{
  GLfloat dot;

  /* Find dot product between light position vector and ground plane normal. */
  dot = groundplane[X] * lightpos[X] +
    groundplane[Y] * lightpos[Y] +
    groundplane[Z] * lightpos[Z] +
    groundplane[W] * lightpos[W];

  shadowMat[0][0] = dot - lightpos[X] * groundplane[X];
  shadowMat[1][0] = 0.f - lightpos[X] * groundplane[Y];
  shadowMat[2][0] = 0.f - lightpos[X] * groundplane[Z];
  shadowMat[3][0] = 0.f - lightpos[X] * groundplane[W];

  shadowMat[X][1] = 0.f - lightpos[Y] * groundplane[X];
  shadowMat[1][1] = dot - lightpos[Y] * groundplane[Y];
  shadowMat[2][1] = 0.f - lightpos[Y] * groundplane[Z];
  shadowMat[3][1] = 0.f - lightpos[Y] * groundplane[W];

  shadowMat[X][2] = 0.f - lightpos[Z] * groundplane[X];
  shadowMat[1][2] = 0.f - lightpos[Z] * groundplane[Y];
  shadowMat[2][2] = dot - lightpos[Z] * groundplane[Z];
  shadowMat[3][2] = 0.f - lightpos[Z] * groundplane[W];

  shadowMat[X][3] = 0.f - lightpos[W] * groundplane[X];
  shadowMat[1][3] = 0.f - lightpos[W] * groundplane[Y];
  shadowMat[2][3] = 0.f - lightpos[W] * groundplane[Z];
  shadowMat[3][3] = dot - lightpos[W] * groundplane[W];

}

/* Find the plane equation given 3 points. */
static void
findPlane(GLfloat plane[4],
  GLfloat v0[3], GLfloat v1[3], GLfloat v2[3])
{
  GLfloat vec0[3], vec1[3];

  /* Need 2 vectors to find cross product. */
  vec0[X] = v1[X] - v0[X];
  vec0[Y] = v1[Y] - v0[Y];
  vec0[Z] = v1[Z] - v0[Z];

  vec1[X] = v2[X] - v0[X];
  vec1[Y] = v2[Y] - v0[Y];
  vec1[Z] = v2[Z] - v0[Z];

  /* find cross product to get A, B, and C of plane equation */
  plane[A] = vec0[Y] * vec1[Z] - vec0[Z] * vec1[Y];
  plane[B] = -(vec0[X] * vec1[Z] - vec0[Z] * vec1[X]);
  plane[C] = vec0[X] * vec1[Y] - vec0[Y] * vec1[X];

  plane[D] = -(plane[A] * v0[X] + plane[B] * v0[Y] + plane[C] * v0[Z]);
}

static void
extrudeSolidFromPolygon(GLfloat data[][2], unsigned int dataSize,
  GLdouble thickness, GLuint side, GLuint edge, GLuint whole)
{
  static GLUtriangulatorObj *tobj = NULL;
  GLdouble vertex[3], dx, dy, len;
  int i;
  int count = (int) (dataSize / (2 * sizeof(GLfloat)));

  if (tobj == NULL) {
    tobj = gluNewTess();  /* create and initialize a GLU
                             polygon tesselation object */
    gluTessCallback(tobj, GLU_BEGIN, glBegin);
    gluTessCallback(tobj, GLU_VERTEX, glVertex2fv);  /* semi-tricky */
    gluTessCallback(tobj, GLU_END, glEnd);
  }
  glNewList(side, GL_COMPILE);
  glShadeModel(GL_SMOOTH);  /* smooth minimizes seeing
                               tessellation */
  gluBeginPolygon(tobj);
  for (i = 0; i < count; i++) {
    vertex[0] = data[i][0];
    vertex[1] = data[i][1];
    vertex[2] = 0;
    gluTessVertex(tobj, vertex, data[i]);
  }
  gluEndPolygon(tobj);
  glEndList();
  glNewList(edge, GL_COMPILE);
  glShadeModel(GL_FLAT);  /* flat shade keeps angular hands
                             from being "smoothed" */
  glBegin(GL_QUAD_STRIP);
  for (i = 0; i <= count; i++) {
#if 1 /* weird, but seems to be legal */
    /* mod function handles closing the edge */
    glVertex3f(data[i % count][0], data[i % count][1], 0.0);
    glVertex3f(data[i % count][0], data[i % count][1], thickness);
    /* Calculate a unit normal by dividing by Euclidean
       distance. We * could be lazy and use
       glEnable(GL_NORMALIZE) so we could pass in * arbitrary
       normals for a very slight performance hit. */
    dx = data[(i + 1) % count][1] - data[i % count][1];
    dy = data[i % count][0] - data[(i + 1) % count][0];
    len = sqrt(dx * dx + dy * dy);
    glNormal3f(dx / len, dy / len, 0.0);
#else /* the nice way of doing it */
    /* Calculate a unit normal by dividing by Euclidean
       distance. We * could be lazy and use
       glEnable(GL_NORMALIZE) so we could pass in * arbitrary
       normals for a very slight performance hit. */
    dx = data[i % count][1] - data[(i - 1 + count) % count][1];
    dy = data[(i - 1 + count) % count][0] - data[i % count][0];
    len = sqrt(dx * dx + dy * dy);
    glNormal3f(dx / len, dy / len, 0.0);
    /* mod function handles closing the edge */
    glVertex3f(data[i % count][0], data[i % count][1], 0.0);
    glVertex3f(data[i % count][0], data[i % count][1], thickness);
#endif
  }
  glEnd();
  glEndList();
  glNewList(whole, GL_COMPILE);
  glFrontFace(GL_CW);
  glCallList(edge);
  glNormal3f(0.0, 0.0, -1.0);  /* constant normal for side */
  glCallList(side);
  glPushMatrix();
  glTranslatef(0.0, 0.0, thickness);
  glFrontFace(GL_CCW);
  glNormal3f(0.0, 0.0, 1.0);  /* opposite normal for other side */
  glCallList(side);
  glPopMatrix();
  glEndList();
}

/* Enumerants for refering to display lists. */
typedef enum {
  RESERVED, BODY_SIDE, BODY_EDGE, BODY_WHOLE, ARM_SIDE, ARM_EDGE, ARM_WHOLE,
  LEG_SIDE, LEG_EDGE, LEG_WHOLE, EYE_SIDE, EYE_EDGE, EYE_WHOLE
} displayLists;

static void
makeDinosaur(void)
{
  extrudeSolidFromPolygon(body, sizeof(body), bodyWidth,
    BODY_SIDE, BODY_EDGE, BODY_WHOLE);
  extrudeSolidFromPolygon(arm, sizeof(arm), bodyWidth / 4,
    ARM_SIDE, ARM_EDGE, ARM_WHOLE);
  extrudeSolidFromPolygon(leg, sizeof(leg), bodyWidth / 2,
    LEG_SIDE, LEG_EDGE, LEG_WHOLE);
  extrudeSolidFromPolygon(eye, sizeof(eye), bodyWidth + 0.2,
    EYE_SIDE, EYE_EDGE, EYE_WHOLE);
}

static void
drawDinosaur(void)

{
  glPushMatrix();
  /* Translate the dinosaur to be at (0,8,0). */
  glTranslatef(-8, 0, -bodyWidth / 2);
  glTranslatef(0.0, jump, 0.0);
  glMaterialfv(GL_FRONT, GL_DIFFUSE, skinColor);
  glCallList(BODY_WHOLE);
  glTranslatef(0.0, 0.0, bodyWidth);
  glCallList(ARM_WHOLE);
  glCallList(LEG_WHOLE);
  glTranslatef(0.0, 0.0, -bodyWidth - bodyWidth / 4);
  glCallList(ARM_WHOLE);
  glTranslatef(0.0, 0.0, -bodyWidth / 4);
  glCallList(LEG_WHOLE);
  glTranslatef(0.0, 0.0, bodyWidth / 2 - 0.1);
  glMaterialfv(GL_FRONT, GL_DIFFUSE, eyeColor);
  glCallList(EYE_WHOLE);
  glPopMatrix();
}

static GLfloat floorVertices[4][3] = {
  { -20.0, 0.0, 20.0 },
  { 20.0, 0.0, 20.0 },
  { 20.0, 0.0, -20.0 },
  { -20.0, 0.0, -20.0 },
};

/* Draw a floor (possibly textured). */
static void
drawFloor(void)
{
  glDisable(GL_LIGHTING);

  if (useTexture) {
    glEnable(GL_TEXTURE_2D);
  }

  glBegin(GL_QUADS);
    glTexCoord2f(0.0, 0.0);
    glVertex3fv(floorVertices[0]);
    glTexCoord2f(0.0, 16.0);
    glVertex3fv(floorVertices[1]);
    glTexCoord2f(16.0, 16.0);
    glVertex3fv(floorVertices[2]);
    glTexCoord2f(16.0, 0.0);
    glVertex3fv(floorVertices[3]);
  glEnd();

  if (useTexture) {
    glDisable(GL_TEXTURE_2D);
  }

  glEnable(GL_LIGHTING);
}

static GLfloat floorPlane[4];
static GLfloat floorShadow[4][4];

static void
redraw(void)
{
  int start, end;

  if (reportSpeed) {
    start = glutGet(GLUT_ELAPSED_TIME);
  }

  /* Clear; default stencil clears to zero. */
  if ((stencilReflection && renderReflection) || (stencilShadow && renderShadow)) {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
  } else {
    /* Avoid clearing stencil when not using it. */
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  }

  /* Reposition the light source. */
  lightPosition[0] = 12*cos(lightAngle);
  lightPosition[1] = lightHeight;
  lightPosition[2] = 12*sin(lightAngle);
  if (directionalLight) {
    lightPosition[3] = 0.0;
  } else {
    lightPosition[3] = 1.0;
  }

  shadowMatrix(floorShadow, floorPlane, lightPosition);

  glPushMatrix();
    /* Perform scene rotations based on user mouse input. */
    glRotatef(angle2, 1.0, 0.0, 0.0);
    glRotatef(angle, 0.0, 1.0, 0.0);
     
    /* Tell GL new light source position. */
    glLightfv(GL_LIGHT0, GL_POSITION, lightPosition);

    if (renderReflection) {
      if (stencilReflection) {
        /* We can eliminate the visual "artifact" of seeing the "flipped"
  	   dinosaur underneath the floor by using stencil.  The idea is
	   draw the floor without color or depth update but so that 
	   a stencil value of one is where the floor will be.  Later when
	   rendering the dinosaur reflection, we will only update pixels
	   with a stencil value of 1 to make sure the reflection only
	   lives on the floor, not below the floor. */

        /* Don't update color or depth. */
        glDisable(GL_DEPTH_TEST);
        glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);

        /* Draw 1 into the stencil buffer. */
        glEnable(GL_STENCIL_TEST);
        glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE);
        glStencilFunc(GL_ALWAYS, 1, 0xffffffff);

        /* Now render floor; floor pixels just get their stencil set to 1. */
        drawFloor();

        /* Re-enable update of color and depth. */ 
        glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
        glEnable(GL_DEPTH_TEST);

        /* Now, only render where stencil is set to 1. */
        glStencilFunc(GL_EQUAL, 1, 0xffffffff);  /* draw if ==1 */
        glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
      }

      glPushMatrix();

        /* The critical reflection step: Reflect dinosaur through the floor
           (the Y=0 plane) to make a relection. */
        glScalef(1.0, -1.0, 1.0);

	/* Reflect the light position. */
        glLightfv(GL_LIGHT0, GL_POSITION, lightPosition);

        /* To avoid our normals getting reversed and hence botched lighting
	   on the reflection, turn on normalize.  */
        glEnable(GL_NORMALIZE);
        glCullFace(GL_FRONT);

        /* Draw the reflected dinosaur. */
        drawDinosaur();

        /* Disable noramlize again and re-enable back face culling. */
        glDisable(GL_NORMALIZE);
        glCullFace(GL_BACK);

      glPopMatrix();

      /* Switch back to the unreflected light position. */
      glLightfv(GL_LIGHT0, GL_POSITION, lightPosition);

      if (stencilReflection) {
        glDisable(GL_STENCIL_TEST);
      }
    }

    /* Back face culling will get used to only draw either the top or the
       bottom floor.  This let's us get a floor with two distinct
       appearances.  The top floor surface is reflective and kind of red.
       The bottom floor surface is not reflective and blue. */

    /* Draw "bottom" of floor in blue. */
    glFrontFace(GL_CW);  /* Switch face orientation. */
    glColor4f(0.1, 0.1, 0.7, 1.0);
    drawFloor();
    glFrontFace(GL_CCW);

    if (renderShadow) {
      if (stencilShadow) {
	/* Draw the floor with stencil value 3.  This helps us only 
	   draw the shadow once per floor pixel (and only on the
	   floor pixels). */
        glEnable(GL_STENCIL_TEST);
        glStencilFunc(GL_ALWAYS, 3, 0xffffffff);
        glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
      }
    }

    /* Draw "top" of floor.  Use blending to blend in reflection. */
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glColor4f(0.7, 0.0, 0.0, 0.3);
    glColor4f(1.0, 1.0, 1.0, 0.3);
    drawFloor();
    glDisable(GL_BLEND);

    if (renderDinosaur) {
      /* Draw "actual" dinosaur, not its reflection. */
      drawDinosaur();
    }

    if (renderShadow) {

      /* Render the projected shadow. */

      if (stencilShadow) {

        /* Now, only render where stencil is set above 2 (ie, 3 where
	   the top floor is).  Update stencil with 2 where the shadow
	   gets drawn so we don't redraw (and accidently reblend) the
	   shadow). */
        glStencilFunc(GL_LESS, 2, 0xffffffff);  /* draw if ==1 */
        glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE);
      }

      /* To eliminate depth buffer artifacts, we use polygon offset
	 to raise the depth of the projected shadow slightly so
	 that it does not depth buffer alias with the floor. */
      if (offsetShadow) {
	switch (polygonOffsetVersion) {
	case EXTENSION:
#ifdef GL_EXT_polygon_offset
	  glEnable(GL_POLYGON_OFFSET_EXT);
	  break;
#endif
#ifdef GL_VERSION_1_1
	case ONE_DOT_ONE:
          glEnable(GL_POLYGON_OFFSET_FILL);
	  break;
#endif
	case MISSING:
	  /* Oh well. */
	  break;
	}
      }

      /* Render 50% black shadow color on top of whatever the
         floor appareance is. */
      glEnable(GL_BLEND);
      glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
      glDisable(GL_LIGHTING);  /* Force the 50% black. */
      glColor4f(0.0, 0.0, 0.0, 0.5);

      glPushMatrix();
	/* Project the shadow. */
        glMultMatrixf((GLfloat *) floorShadow);
        drawDinosaur();
      glPopMatrix();

      glDisable(GL_BLEND);
      glEnable(GL_LIGHTING);

      if (offsetShadow) {
	switch (polygonOffsetVersion) {
#ifdef GL_EXT_polygon_offset
	case EXTENSION:
	  glDisable(GL_POLYGON_OFFSET_EXT);
	  break;
#endif
#ifdef GL_VERSION_1_1
	case ONE_DOT_ONE:
          glDisable(GL_POLYGON_OFFSET_FILL);
	  break;
#endif
	case MISSING:
	  /* Oh well. */
	  break;
	}
      }
      if (stencilShadow) {
        glDisable(GL_STENCIL_TEST);
      }
    }

    glPushMatrix();
    glDisable(GL_LIGHTING);
    glColor3f(1.0, 1.0, 0.0);
    if (directionalLight) {
      /* Draw an arrowhead. */
      glDisable(GL_CULL_FACE);
      glTranslatef(lightPosition[0], lightPosition[1], lightPosition[2]);
      glRotatef(lightAngle * -180.0 / M_PI, 0, 1, 0);
      glRotatef(atan(lightHeight/12) * 180.0 / M_PI, 0, 0, 1);
      glBegin(GL_TRIANGLE_FAN);
	glVertex3f(0, 0, 0);
	glVertex3f(2, 1, 1);
	glVertex3f(2, -1, 1);
	glVertex3f(2, -1, -1);
	glVertex3f(2, 1, -1);
	glVertex3f(2, 1, 1);
      glEnd();
      /* Draw a white line from light direction. */
      glColor3f(1.0, 1.0, 1.0);
      glBegin(GL_LINES);
	glVertex3f(0, 0, 0);
	glVertex3f(5, 0, 0);
      glEnd();
      glEnable(GL_CULL_FACE);
    } else {
      /* Draw a yellow ball at the light source. */
      glTranslatef(lightPosition[0], lightPosition[1], lightPosition[2]);
      glutSolidSphere(1.0, 5, 5);
    }
    glEnable(GL_LIGHTING);
    glPopMatrix();

  glPopMatrix();

  if (reportSpeed) {
    glFinish();
    end = glutGet(GLUT_ELAPSED_TIME);
    printf("Speed %.3g frames/sec (%d ms)\n", 1000.0/(end-start), end-start);
  }

  glutSwapBuffers();
}

/* ARGSUSED2 */
static void
mouse(int button, int state, int x, int y)
{
  if (button == GLUT_LEFT_BUTTON) {
    if (state == GLUT_DOWN) {
      moving = 1;
      startx = x;
      starty = y;
    }
    if (state == GLUT_UP) {
      moving = 0;
    }
  }
  if (button == GLUT_MIDDLE_BUTTON) {
    if (state == GLUT_DOWN) {
      lightMoving = 1;
      lightStartX = x;
      lightStartY = y;
    }
    if (state == GLUT_UP) {
      lightMoving = 0;
    }
  }
}

/* ARGSUSED1 */
static void
motion(int x, int y)
{
  if (moving) {
    angle = angle + (x - startx);
    angle2 = angle2 + (y - starty);
    startx = x;
    starty = y;
    glutPostRedisplay();
  }
  if (lightMoving) {
    lightAngle += (x - lightStartX)/40.0;
    lightHeight += (lightStartY - y)/20.0;
    lightStartX = x;
    lightStartY = y;
    glutPostRedisplay();
  }
}

/* Advance time varying state when idle callback registered. */
static void
idle(void)
{
  static float time = 0.0;

  time = glutGet(GLUT_ELAPSED_TIME) / 500.0;

  jump = 4.0 * fabs(sin(time)*0.5);
  if (!lightMoving) {
    lightAngle += 0.03;
  }
  glutPostRedisplay();
}

enum {
  M_NONE, M_MOTION, M_LIGHT, M_TEXTURE, M_SHADOWS, M_REFLECTION, M_DINOSAUR,
  M_STENCIL_REFLECTION, M_STENCIL_SHADOW, M_OFFSET_SHADOW,
  M_POSITIONAL, M_DIRECTIONAL, M_PERFORMANCE
};

static void
controlLights(int value)
{
  switch (value) {
  case M_NONE:
    return;
  case M_MOTION:
    animation = 1 - animation;
    if (animation) {
      glutIdleFunc(idle);
    } else {
      glutIdleFunc(NULL);
    }
    break;
  case M_LIGHT:
    lightSwitch = !lightSwitch;
    if (lightSwitch) {
      glEnable(GL_LIGHT0);
    } else {
      glDisable(GL_LIGHT0);
    }
    break;
  case M_TEXTURE:
    useTexture = !useTexture;
    break;
  case M_SHADOWS:
    renderShadow = 1 - renderShadow;
    break;
  case M_REFLECTION:
    renderReflection = 1 - renderReflection;
    break;
  case M_DINOSAUR:
    renderDinosaur = 1 - renderDinosaur;
    break;
  case M_STENCIL_REFLECTION:
    stencilReflection = 1 - stencilReflection;
    break;
  case M_STENCIL_SHADOW:
    stencilShadow = 1 - stencilShadow;
    break;
  case M_OFFSET_SHADOW:
    offsetShadow = 1 - offsetShadow;
    break;
  case M_POSITIONAL:
    directionalLight = 0;
    break;
  case M_DIRECTIONAL:
    directionalLight = 1;
    break;
  case M_PERFORMANCE:
    reportSpeed = 1 - reportSpeed;
    break;
  }
  glutPostRedisplay();
}

/* When not visible, stop animating.  Restart when visible again. */
static void 
visible(int vis)
{
  if (vis == GLUT_VISIBLE) {
    if (animation)
      glutIdleFunc(idle);
  } else {
    if (!animation)
      glutIdleFunc(NULL);
  }
}

/* Press any key to redraw; good when motion stopped and
   performance reporting on. */
/* ARGSUSED */
static void
key(unsigned char c, int x, int y)
{
  if (c == 27) {
    exit(0);  /* IRIS GLism, Escape quits. */
  }
  glutPostRedisplay();
}

/* Press any key to redraw; good when motion stopped and
   performance reporting on. */
/* ARGSUSED */
static void
special(int k, int x, int y)
{
  glutPostRedisplay();
}

static int
supportsOneDotOne(void)
{
  const char *version;
  int major, minor;

  version = (char *) glGetString(GL_VERSION);
  if (sscanf(version, "%d.%d", &major, &minor) == 2)
    return major * 10 + minor >= 11;
  return 0;            /* OpenGL version string malformed! */
}

int
main(int argc, char **argv)
{
  int i;

  glutInit(&argc, argv);

  for (i=1; i<argc; i++) {
    if (!strcmp("-linear", argv[i])) {
      linearFiltering = 1;
    } else if (!strcmp("-mipmap", argv[i])) {
      useMipmaps = 1;
    } else if (!strcmp("-ext", argv[i])) {
      forceExtension = 1;
    }
  }

  glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH | GLUT_STENCIL);

#if 0
  /* In GLUT 4.0, you'll be able to do this an be sure to
     get 2 bits of stencil if the machine has it for you. */
  glutInitDisplayString("samples stencil>=2 rgb double depth");
#endif

  glutCreateWindow("Shadowy Leapin' Lizards");
  glewInit();

  if (glutGet(GLUT_WINDOW_STENCIL_SIZE) <= 1) {
    printf("dinoshade: Sorry, I need at least 2 bits of stencil.\n");
    exit(1);
  }

  /* Register GLUT callbacks. */
  glutDisplayFunc(redraw);
  glutMouseFunc(mouse);
  glutMotionFunc(motion);
  glutVisibilityFunc(visible);
  glutKeyboardFunc(key);
  glutSpecialFunc(special);

  glutCreateMenu(controlLights);

  glutAddMenuEntry("Toggle motion", M_MOTION);
  glutAddMenuEntry("-----------------------", M_NONE);
  glutAddMenuEntry("Toggle light", M_LIGHT);
  glutAddMenuEntry("Toggle texture", M_TEXTURE);
  glutAddMenuEntry("Toggle shadows", M_SHADOWS);
  glutAddMenuEntry("Toggle reflection", M_REFLECTION);
  glutAddMenuEntry("Toggle dinosaur", M_DINOSAUR);
  glutAddMenuEntry("-----------------------", M_NONE);
  glutAddMenuEntry("Toggle reflection stenciling", M_STENCIL_REFLECTION);
  glutAddMenuEntry("Toggle shadow stenciling", M_STENCIL_SHADOW);
  glutAddMenuEntry("Toggle shadow offset", M_OFFSET_SHADOW);
  glutAddMenuEntry("----------------------", M_NONE);
  glutAddMenuEntry("Positional light", M_POSITIONAL);
  glutAddMenuEntry("Directional light", M_DIRECTIONAL);
  glutAddMenuEntry("-----------------------", M_NONE);
  glutAddMenuEntry("Toggle performance", M_PERFORMANCE);
  glutAttachMenu(GLUT_RIGHT_BUTTON);
  makeDinosaur();

#ifdef GL_VERSION_1_1
  if (supportsOneDotOne() && !forceExtension) {
    polygonOffsetVersion = ONE_DOT_ONE;
    glPolygonOffset(-2.0, -9.0);
  } else
#endif
  {
#ifdef GL_EXT_polygon_offset
  /* check for the polygon offset extension */
  if (glutExtensionSupported("GL_EXT_polygon_offset")) {
    polygonOffsetVersion = EXTENSION;
    glPolygonOffsetEXT(-2.0, -0.002);
  } else 
#endif
    {
      polygonOffsetVersion = MISSING;
      printf("\ndinoshine: Missing polygon offset.\n");
      printf("           Expect shadow depth aliasing artifacts.\n\n");
    }
  }

  glEnable(GL_CULL_FACE);
  glEnable(GL_DEPTH_TEST);
  glEnable(GL_TEXTURE_2D);
  glLineWidth(3.0);

  glMatrixMode(GL_PROJECTION);
  gluPerspective( /* field of view in degree */ 40.0,
  /* aspect ratio */ 1.0,
    /* Z near */ 20.0, /* Z far */ 100.0);
  glMatrixMode(GL_MODELVIEW);
  gluLookAt(0.0, 8.0, 60.0,  /* eye is at (0,8,60) */
    0.0, 8.0, 0.0,      /* center is at (0,8,0) */
    0.0, 1.0, 0.);      /* up is in postivie Y direction */

  glLightModeli(GL_LIGHT_MODEL_LOCAL_VIEWER, 1);
  glLightfv(GL_LIGHT0, GL_DIFFUSE, lightColor);
  glLightf(GL_LIGHT0, GL_CONSTANT_ATTENUATION, 0.1);
  glLightf(GL_LIGHT0, GL_LINEAR_ATTENUATION, 0.05);
  glEnable(GL_LIGHT0);
  glEnable(GL_LIGHTING);

  makeFloorTexture();

  /* Setup floor plane for projected shadow calculations. */
  findPlane(floorPlane, floorVertices[1], floorVertices[2], floorVertices[3]);

  glutMainLoop();
  return 0;             /* ANSI C requires main to return int. */
}