1/*
2 * Use glCopyTexSubImage2D to draw animated gears on the sides of a box.
3 *
4 * Brian Paul
5 * 27 January 2006
6 */
7
8#include <math.h>
9#include <stdlib.h>
10#include <stdio.h>
11#include <string.h>
12#include "glut_wrap.h"
13
14#ifndef M_PI
15#define M_PI 3.14159265
16#endif
17
18static GLint WinWidth = 800, WinHeight = 500;
19static GLint TexWidth, TexHeight;
20static GLuint TexObj = 1;
21static GLenum IntFormat = GL_RGB;
22
23static GLboolean WireFrame = GL_FALSE;
24
25static GLint T0 = 0;
26static GLint Frames = 0;
27static GLint Win = 0;
28
29static GLfloat ViewRotX = 20.0, ViewRotY = 30.0, ViewRotZ = 0.0;
30static GLint Gear1, Gear2, Gear3;
31static GLfloat GearRot = 0.0;
32static GLfloat CubeRot = 0.0;
33
34
35/**
36  Draw a gear wheel.  You'll probably want to call this function when
37  building a display list since we do a lot of trig here.
38
39  Input:  inner_radius - radius of hole at center
40          outer_radius - radius at center of teeth
41          width - width of gear
42          teeth - number of teeth
43          tooth_depth - depth of tooth
44 **/
45static void
46gear(GLfloat inner_radius, GLfloat outer_radius, GLfloat width,
47     GLint teeth, GLfloat tooth_depth)
48{
49  GLint i;
50  GLfloat r0, r1, r2;
51  GLfloat angle, da;
52  GLfloat u, v, len;
53
54  r0 = inner_radius;
55  r1 = outer_radius - tooth_depth / 2.0;
56  r2 = outer_radius + tooth_depth / 2.0;
57
58  da = 2.0 * M_PI / teeth / 4.0;
59
60  glShadeModel(GL_FLAT);
61
62  glNormal3f(0.0, 0.0, 1.0);
63
64  /* draw front face */
65  glBegin(GL_QUAD_STRIP);
66  for (i = 0; i <= teeth; i++) {
67    angle = i * 2.0 * M_PI / teeth;
68    glVertex3f(r0 * cos(angle), r0 * sin(angle), width * 0.5);
69    glVertex3f(r1 * cos(angle), r1 * sin(angle), width * 0.5);
70    if (i < teeth) {
71      glVertex3f(r0 * cos(angle), r0 * sin(angle), width * 0.5);
72      glVertex3f(r1 * cos(angle + 3 * da), r1 * sin(angle + 3 * da), width * 0.5);
73    }
74  }
75  glEnd();
76
77  /* draw front sides of teeth */
78  glBegin(GL_QUADS);
79  da = 2.0 * M_PI / teeth / 4.0;
80  for (i = 0; i < teeth; i++) {
81    angle = i * 2.0 * M_PI / teeth;
82
83    glVertex3f(r1 * cos(angle), r1 * sin(angle), width * 0.5);
84    glVertex3f(r2 * cos(angle + da), r2 * sin(angle + da), width * 0.5);
85    glVertex3f(r2 * cos(angle + 2 * da), r2 * sin(angle + 2 * da), width * 0.5);
86    glVertex3f(r1 * cos(angle + 3 * da), r1 * sin(angle + 3 * da), width * 0.5);
87  }
88  glEnd();
89
90  glNormal3f(0.0, 0.0, -1.0);
91
92  /* draw back face */
93  glBegin(GL_QUAD_STRIP);
94  for (i = 0; i <= teeth; i++) {
95    angle = i * 2.0 * M_PI / teeth;
96    glVertex3f(r1 * cos(angle), r1 * sin(angle), -width * 0.5);
97    glVertex3f(r0 * cos(angle), r0 * sin(angle), -width * 0.5);
98    if (i < teeth) {
99      glVertex3f(r1 * cos(angle + 3 * da), r1 * sin(angle + 3 * da), -width * 0.5);
100      glVertex3f(r0 * cos(angle), r0 * sin(angle), -width * 0.5);
101    }
102  }
103  glEnd();
104
105  /* draw back sides of teeth */
106  glBegin(GL_QUADS);
107  da = 2.0 * M_PI / teeth / 4.0;
108  for (i = 0; i < teeth; i++) {
109    angle = i * 2.0 * M_PI / teeth;
110
111    glVertex3f(r1 * cos(angle + 3 * da), r1 * sin(angle + 3 * da), -width * 0.5);
112    glVertex3f(r2 * cos(angle + 2 * da), r2 * sin(angle + 2 * da), -width * 0.5);
113    glVertex3f(r2 * cos(angle + da), r2 * sin(angle + da), -width * 0.5);
114    glVertex3f(r1 * cos(angle), r1 * sin(angle), -width * 0.5);
115  }
116  glEnd();
117
118  /* draw outward faces of teeth */
119  glBegin(GL_QUAD_STRIP);
120  for (i = 0; i < teeth; i++) {
121    angle = i * 2.0 * M_PI / teeth;
122
123    glVertex3f(r1 * cos(angle), r1 * sin(angle), width * 0.5);
124    glVertex3f(r1 * cos(angle), r1 * sin(angle), -width * 0.5);
125    u = r2 * cos(angle + da) - r1 * cos(angle);
126    v = r2 * sin(angle + da) - r1 * sin(angle);
127    len = sqrt(u * u + v * v);
128    u /= len;
129    v /= len;
130    glNormal3f(v, -u, 0.0);
131    glVertex3f(r2 * cos(angle + da), r2 * sin(angle + da), width * 0.5);
132    glVertex3f(r2 * cos(angle + da), r2 * sin(angle + da), -width * 0.5);
133    glNormal3f(cos(angle), sin(angle), 0.0);
134    glVertex3f(r2 * cos(angle + 2 * da), r2 * sin(angle + 2 * da), width * 0.5);
135    glVertex3f(r2 * cos(angle + 2 * da), r2 * sin(angle + 2 * da), -width * 0.5);
136    u = r1 * cos(angle + 3 * da) - r2 * cos(angle + 2 * da);
137    v = r1 * sin(angle + 3 * da) - r2 * sin(angle + 2 * da);
138    glNormal3f(v, -u, 0.0);
139    glVertex3f(r1 * cos(angle + 3 * da), r1 * sin(angle + 3 * da), width * 0.5);
140    glVertex3f(r1 * cos(angle + 3 * da), r1 * sin(angle + 3 * da), -width * 0.5);
141    glNormal3f(cos(angle), sin(angle), 0.0);
142  }
143
144  glVertex3f(r1 * cos(0), r1 * sin(0), width * 0.5);
145  glVertex3f(r1 * cos(0), r1 * sin(0), -width * 0.5);
146
147  glEnd();
148
149  glShadeModel(GL_SMOOTH);
150
151  /* draw inside radius cylinder */
152  glBegin(GL_QUAD_STRIP);
153  for (i = 0; i <= teeth; i++) {
154    angle = i * 2.0 * M_PI / teeth;
155    glNormal3f(-cos(angle), -sin(angle), 0.0);
156    glVertex3f(r0 * cos(angle), r0 * sin(angle), -width * 0.5);
157    glVertex3f(r0 * cos(angle), r0 * sin(angle), width * 0.5);
158  }
159  glEnd();
160
161}
162
163static void
164cleanup(void)
165{
166   glDeleteTextures(1, &TexObj);
167   glDeleteLists(Gear1, 1);
168   glDeleteLists(Gear2, 1);
169   glDeleteLists(Gear3, 1);
170   glutDestroyWindow(Win);
171}
172
173
174static void
175DrawGears(void)
176{
177   if (WireFrame) {
178      glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
179   }
180
181   glPushMatrix();
182      glRotatef(20/*ViewRotX*/, 1.0, 0.0, 0.0);
183      glRotatef(ViewRotY, 0.0, 1.0, 0.0);
184      glRotatef(ViewRotZ, 0.0, 0.0, 1.0);
185
186      glPushMatrix();
187         glTranslatef(-3.0, -2.0, 0.0);
188         glRotatef(GearRot, 0.0, 0.0, 1.0);
189         glCallList(Gear1);
190      glPopMatrix();
191
192      glPushMatrix();
193         glTranslatef(3.1, -2.0, 0.0);
194         glRotatef(-2.0 * GearRot - 9.0, 0.0, 0.0, 1.0);
195         glCallList(Gear2);
196      glPopMatrix();
197
198      glPushMatrix();
199         glTranslatef(-3.1, 4.2, 0.0);
200         glRotatef(-2.0 * GearRot - 25.0, 0.0, 0.0, 1.0);
201         glCallList(Gear3);
202      glPopMatrix();
203
204  glPopMatrix();
205
206  glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
207}
208
209
210static void
211DrawCube(void)
212{
213   static const GLfloat texcoords[4][2] = {
214      { 0, 0 }, { 1, 0 }, { 1, 1 }, { 0, 1 }
215   };
216   static const GLfloat vertices[4][2] = {
217      { -1, -1 }, { 1, -1 }, { 1, 1 }, { -1, 1 }
218   };
219   static const GLfloat xforms[6][4] = {
220      {   0, 0, 1, 0 },
221      {  90, 0, 1, 0 },
222      { 180, 0, 1, 0 },
223      { 270, 0, 1, 0 },
224      {  90, 1, 0, 0 },
225      { -90, 1, 0, 0 }
226   };
227   static const GLfloat mat[4] = { 1.0, 1.0, 0.5, 1.0 };
228   GLint i, j;
229
230   glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, mat);
231   glEnable(GL_TEXTURE_2D);
232
233   glPushMatrix();
234      glRotatef(ViewRotX, 1.0, 0.0, 0.0);
235      glRotatef(15, 1, 0, 0);
236      glRotatef(CubeRot, 0, 1, 0);
237      glScalef(4, 4, 4);
238
239      for (i = 0; i < 6; i++) {
240         glPushMatrix();
241            glRotatef(xforms[i][0], xforms[i][1], xforms[i][2], xforms[i][3]);
242            glTranslatef(0, 0, 1.1);
243            glBegin(GL_POLYGON);
244               glNormal3f(0, 0, 1);
245               for (j = 0; j < 4; j++) {
246                  glTexCoord2fv(texcoords[j]);
247                  glVertex2fv(vertices[j]);
248               }
249            glEnd();
250         glPopMatrix();
251      }
252   glPopMatrix();
253
254   glDisable(GL_TEXTURE_2D);
255}
256
257
258static void
259draw(void)
260{
261   float ar;
262
263   glMatrixMode(GL_MODELVIEW);
264   glLoadIdentity();
265   glTranslatef(0.0, 0.0, -40.0);
266
267   /* clear whole depth buffer */
268   glDisable(GL_SCISSOR_TEST);
269   glClear(GL_DEPTH_BUFFER_BIT);
270   glEnable(GL_SCISSOR_TEST);
271
272   /* clear upper-left corner of color buffer (unused space) */
273   glScissor(0, TexHeight, TexWidth, WinHeight - TexHeight);
274   glClearColor(0.0, 0.0, 0.0, 0.0);
275   glClear(GL_COLOR_BUFFER_BIT);
276
277   /* clear lower-left corner of color buffer */
278   glViewport(0, 0, TexWidth, TexHeight);
279   glScissor(0, 0, TexWidth, TexHeight);
280   glClearColor(1, 1, 1, 0);
281   glClear(GL_COLOR_BUFFER_BIT);
282
283   /* draw gears in lower-left corner */
284   glMatrixMode(GL_PROJECTION);
285   glLoadIdentity();
286   glFrustum(-1.0, 1.0, -1.0, 1.0, 5.0, 60.0);
287   glMatrixMode(GL_MODELVIEW);
288   DrawGears();
289
290   /* copy color buffer to texture */
291   glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, TexWidth, TexHeight);
292
293   /* clear right half of color buffer */
294   glViewport(TexWidth, 0, WinWidth - TexWidth, WinHeight);
295   glScissor(TexWidth, 0, WinWidth - TexWidth, WinHeight);
296   glClearColor(0.5, 0.5, 0.8, 0.0);
297   glClear(GL_COLOR_BUFFER_BIT);
298
299   /* draw textured cube in right half of window */
300   ar = (float) (WinWidth - TexWidth) / WinHeight;
301   glMatrixMode(GL_PROJECTION);
302   glLoadIdentity();
303   glFrustum(-ar, ar, -1.0, 1.0, 5.0, 60.0);
304   glMatrixMode(GL_MODELVIEW);
305   DrawCube();
306
307   /* finish up */
308   glutSwapBuffers();
309
310   Frames++;
311   {
312      GLint t = glutGet(GLUT_ELAPSED_TIME);
313      if (t - T0 >= 5000) {
314         GLfloat seconds = (t - T0) / 1000.0;
315         GLfloat fps = Frames / seconds;
316         printf("%d frames in %6.3f seconds = %6.3f FPS\n", Frames, seconds, fps);
317         fflush(stdout);
318         T0 = t;
319         Frames = 0;
320      }
321   }
322}
323
324
325static void
326idle(void)
327{
328  static double t0 = -1.;
329  double dt, t = glutGet(GLUT_ELAPSED_TIME) / 1000.0;
330  if (t0 < 0.0)
331    t0 = t;
332  dt = t - t0;
333  t0 = t;
334
335  /* fmod to prevent overflow */
336  GearRot = fmod(GearRot + 70.0 * dt, 360.0);  /* 70 deg/sec */
337  CubeRot = fmod(CubeRot + 15.0 * dt, 360.0);  /* 15 deg/sec */
338
339  glutPostRedisplay();
340}
341
342
343/* change view angle, exit upon ESC */
344static void
345key(unsigned char k, int x, int y)
346{
347   (void) x;
348   (void) y;
349   switch (k) {
350   case 'w':
351      WireFrame = !WireFrame;
352      break;
353   case 'z':
354      ViewRotZ += 5.0;
355      break;
356   case 'Z':
357      ViewRotZ -= 5.0;
358      break;
359   case 27:  /* Escape */
360      cleanup();
361      exit(0);
362      break;
363   default:
364      return;
365   }
366   glutPostRedisplay();
367}
368
369/* change view angle */
370static void
371special(int k, int x, int y)
372{
373   (void) x;
374   (void) y;
375   switch (k) {
376   case GLUT_KEY_UP:
377      ViewRotX += 5.0;
378      break;
379   case GLUT_KEY_DOWN:
380      ViewRotX -= 5.0;
381      break;
382   case GLUT_KEY_LEFT:
383      ViewRotY += 5.0;
384      break;
385   case GLUT_KEY_RIGHT:
386      ViewRotY -= 5.0;
387      break;
388   default:
389      return;
390   }
391   glutPostRedisplay();
392}
393
394
395/* new window size or exposure */
396static void
397reshape(int width, int height)
398{
399  WinWidth = width;
400  WinHeight = height;
401}
402
403
404static void
405init(int argc, char *argv[])
406{
407  static GLfloat pos[4] = {5.0, 5.0, 10.0, 0.0};
408  static GLfloat red[4] = {0.8, 0.1, 0.0, 1.0};
409  static GLfloat green[4] = {0.0, 0.8, 0.2, 1.0};
410  static GLfloat blue[4] = {0.2, 0.2, 1.0, 1.0};
411  GLint i;
412
413  glLightfv(GL_LIGHT0, GL_POSITION, pos);
414#if 0
415  glEnable(GL_CULL_FACE);
416#endif
417  glEnable(GL_LIGHTING);
418  glEnable(GL_LIGHT0);
419  glEnable(GL_DEPTH_TEST);
420
421  /* make the gears */
422  Gear1 = glGenLists(1);
423  glNewList(Gear1, GL_COMPILE);
424  glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, red);
425  gear(1.0, 4.0, 1.0, 20, 0.7);
426  glEndList();
427
428  Gear2 = glGenLists(1);
429  glNewList(Gear2, GL_COMPILE);
430  glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, green);
431  gear(0.5, 2.0, 2.0, 10, 0.7);
432  glEndList();
433
434  Gear3 = glGenLists(1);
435  glNewList(Gear3, GL_COMPILE);
436  glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, blue);
437  gear(1.3, 2.0, 0.5, 10, 0.7);
438  glEndList();
439
440  glEnable(GL_NORMALIZE);
441
442  /* xxx make size dynamic */
443  TexWidth = 256;
444  TexHeight = 256;
445
446   glBindTexture(GL_TEXTURE_2D, TexObj);
447   glTexImage2D(GL_TEXTURE_2D, 0, IntFormat, TexWidth, TexHeight, 0,
448                GL_RGBA, GL_UNSIGNED_BYTE, NULL);
449   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
450   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
451   glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
452
453  for ( i=1; i<argc; i++ ) {
454    if (strcmp(argv[i], "-info")==0) {
455      printf("GL_RENDERER   = %s\n", (char *) glGetString(GL_RENDERER));
456      printf("GL_VERSION    = %s\n", (char *) glGetString(GL_VERSION));
457      printf("GL_VENDOR     = %s\n", (char *) glGetString(GL_VENDOR));
458      printf("GL_EXTENSIONS = %s\n", (char *) glGetString(GL_EXTENSIONS));
459    }
460  }
461}
462
463
464static void
465visible(int vis)
466{
467  if (vis == GLUT_VISIBLE)
468    glutIdleFunc(idle);
469  else
470    glutIdleFunc(NULL);
471}
472
473
474int
475main(int argc, char *argv[])
476{
477   glutInitWindowSize(WinWidth, WinHeight);
478   glutInit(&argc, argv);
479   glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
480
481   Win = glutCreateWindow("gearbox");
482   init(argc, argv);
483
484   glutDisplayFunc(draw);
485   glutReshapeFunc(reshape);
486   glutKeyboardFunc(key);
487   glutSpecialFunc(special);
488   glutVisibilityFunc(visible);
489
490   glutMainLoop();
491   return 0;             /* ANSI C requires main to return int. */
492}
493