/* gears4.c  from mesa deoms, counts frames per second */
/* Command line options:                               */
/*    -info      print GL implementation information   */
/*    -exit      automatically exit after 30 seconds   */
/* arrow keys rotate about X or Y axis, 'z' and 'Z'    */

#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <GL/glut.h>

#ifndef M_PI
#define M_PI 3.14159265
#endif

static GLint T0 = 0;
static GLint Frames = 0;
static GLint autoexit = 0;
static int winHeight = 500;
static int winWidth  = 500;
static int background = 0;

/* Draw a gear wheel.                                */
/* Input:  inner_radius - radius of hole at center   */
/*         outer_radius - radius at center of teeth  */
/*         width - width of gear                     */
/*         teeth - number of teeth                   */
/*         tooth_depth - depth of tooth              */

static void gear(GLfloat inner_radius, GLfloat outer_radius, GLfloat width,
                 GLint teeth, GLfloat tooth_depth)
{
  GLint i;
  GLfloat r0, r1, r2;
  GLfloat angle, da;
  GLfloat u, v, len;

  r0 = inner_radius;
  r1 = outer_radius - tooth_depth / 2.0;
  r2 = outer_radius + tooth_depth / 2.0;
  da = 2.0 * M_PI / teeth / 4.0;
  glShadeModel(GL_FLAT);
  glNormal3f(0.0, 0.0, 1.0);

  /* draw front face */
  glBegin(GL_QUAD_STRIP);
  for (i = 0; i <= teeth; i++) {
    angle = i * 2.0 * M_PI / teeth;
    glVertex3f(r0 * cos(angle), r0 * sin(angle), width * 0.5);
    glVertex3f(r1 * cos(angle), r1 * sin(angle), width * 0.5);
    if (i < teeth) {
      glVertex3f(r0 * cos(angle), r0 * sin(angle), width * 0.5);
      glVertex3f(r1 * cos(angle + 3 * da), r1 * sin(angle + 3 * da), width * 0.5);
    }
  }
  glEnd();

  /* draw front sides of teeth */
  glBegin(GL_QUADS);
  da = 2.0 * M_PI / teeth / 4.0;
  for (i = 0; i < teeth; i++) {
    angle = i * 2.0 * M_PI / teeth;
    glVertex3f(r1 * cos(angle), r1 * sin(angle), width * 0.5);
    glVertex3f(r2 * cos(angle + da), r2 * sin(angle + da), width * 0.5);
    glVertex3f(r2 * cos(angle + 2 * da), r2 * sin(angle + 2 * da), width * 0.5);
    glVertex3f(r1 * cos(angle + 3 * da), r1 * sin(angle + 3 * da), width * 0.5);
  }
  glEnd();
  glNormal3f(0.0, 0.0, -1.0);

  /* draw back face */
  glBegin(GL_QUAD_STRIP);
  for (i = 0; i <= teeth; i++) {
    angle = i * 2.0 * M_PI / teeth;
    glVertex3f(r1 * cos(angle), r1 * sin(angle), -width * 0.5);
    glVertex3f(r0 * cos(angle), r0 * sin(angle), -width * 0.5);
    if (i < teeth) {
      glVertex3f(r1 * cos(angle + 3 * da), r1 * sin(angle + 3 * da), -width * 0.5);
      glVertex3f(r0 * cos(angle), r0 * sin(angle), -width * 0.5);
    }
  }
  glEnd();

  /* draw back sides of teeth */
  glBegin(GL_QUADS);
  da = 2.0 * M_PI / teeth / 4.0;
  for (i = 0; i < teeth; i++) {
    angle = i * 2.0 * M_PI / teeth;
    glVertex3f(r1 * cos(angle + 3 * da), r1 * sin(angle + 3 * da), -width * 0.5);
    glVertex3f(r2 * cos(angle + 2 * da), r2 * sin(angle + 2 * da), -width * 0.5);
    glVertex3f(r2 * cos(angle + da), r2 * sin(angle + da), -width * 0.5);
    glVertex3f(r1 * cos(angle), r1 * sin(angle), -width * 0.5);
  }
  glEnd();

  /* draw outward faces of teeth */
  glBegin(GL_QUAD_STRIP);
  for (i = 0; i < teeth; i++) {
    angle = i * 2.0 * M_PI / teeth;
    glVertex3f(r1 * cos(angle), r1 * sin(angle), width * 0.5);
    glVertex3f(r1 * cos(angle), r1 * sin(angle), -width * 0.5);
    u = r2 * cos(angle + da) - r1 * cos(angle);
    v = r2 * sin(angle + da) - r1 * sin(angle);
    len = sqrt(u * u + v * v);
    u /= len;
    v /= len;
    glNormal3f(v, -u, 0.0);
    glVertex3f(r2 * cos(angle + da), r2 * sin(angle + da), width * 0.5);
    glVertex3f(r2 * cos(angle + da), r2 * sin(angle + da), -width * 0.5);
    glNormal3f(cos(angle), sin(angle), 0.0);
    glVertex3f(r2 * cos(angle + 2 * da), r2 * sin(angle + 2 * da), width * 0.5);
    glVertex3f(r2 * cos(angle + 2 * da), r2 * sin(angle + 2 * da), -width * 0.5);
    u = r1 * cos(angle + 3 * da) - r2 * cos(angle + 2 * da);
    v = r1 * sin(angle + 3 * da) - r2 * sin(angle + 2 * da);
    glNormal3f(v, -u, 0.0);
    glVertex3f(r1 * cos(angle + 3 * da), r1 * sin(angle + 3 * da), width * 0.5);
    glVertex3f(r1 * cos(angle + 3 * da), r1 * sin(angle + 3 * da), -width * 0.5);
    glNormal3f(cos(angle), sin(angle), 0.0);
  }
    glVertex3f(r1 * cos(0), r1 * sin(0), width * 0.5);
    glVertex3f(r1 * cos(0), r1 * sin(0), -width * 0.5);
  glEnd();
  glShadeModel(GL_SMOOTH);

  /* draw inside radius cylinder */
  glBegin(GL_QUAD_STRIP);
  for (i = 0; i <= teeth; i++) {
    angle = i * 2.0 * M_PI / teeth;
    glNormal3f(-cos(angle), -sin(angle), 0.0);
    glVertex3f(r0 * cos(angle), r0 * sin(angle), -width * 0.5);
    glVertex3f(r0 * cos(angle), r0 * sin(angle), width * 0.5);
  }
  glEnd();
} /* end of gear drawing function */

static void drawText(void)
{
  char  msg1[] = "'A' or 'a' for rotation speed";
  char  msg2[] = "arrows and 'Z' or 'z' rotation about axis";
  GLfloat wht[4] = {1.0, 1.0, 1.0, 1.0};
  int   i, len;

  /* Draw text */
  glMatrixMode(GL_PROJECTION);
  glPushMatrix();
    glLoadIdentity();
    glOrtho(0, winWidth, 0, winHeight, -1, 1);
    glMatrixMode(GL_MODELVIEW);
    glPushMatrix();
      glLoadIdentity();
      glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, wht);
      glRasterPos2i(10, 10);
      len = strlen(msg1);
      for (i=0; i<len; i++)
        glutBitmapCharacter(GLUT_BITMAP_TIMES_ROMAN_24, msg1[i]);
      glRasterPos2i(10, 40);
      len = strlen(msg2);
      for (i=0; i<len; i++)
        glutBitmapCharacter(GLUT_BITMAP_TIMES_ROMAN_24, msg2[i]);
      glMatrixMode(GL_PROJECTION);
    glPopMatrix();
    glMatrixMode(GL_MODELVIEW);
  glPopMatrix();
}

static GLfloat view_rotx = 20.0, view_roty = 30.0, view_rotz = 0.0;
static GLint gear1, gear2, gear3;
static GLint gear4; /* JSS */
static GLfloat angle = 0.0;
static GLfloat incAngle = 1.0;

static void draw(void)
{
  if(background) glClearColor(1.0, 1.0, 1.0, 1.0);
  else           glClearColor(0.0, 0.0, 0.0, 1.0);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glPushMatrix();
    glRotatef(view_rotx, 1.0, 0.0, 0.0);
    glRotatef(view_roty, 0.0, 1.0, 0.0);
    glRotatef(view_rotz, 0.0, 0.0, 1.0);

    glPushMatrix();
      glTranslatef(-3.0, -2.0, 0.0);
      glRotatef(angle, 0.0, 0.0, 1.0);
      glCallList(gear1);
    glPopMatrix();

    glPushMatrix();
      glTranslatef(3.1, -2.0, 0.0);
      glRotatef(-2.0 * angle - 9.0, 0.0, 0.0, 1.0);
      glCallList(gear2);
    glPopMatrix();

    glPushMatrix();
      glTranslatef(-3.1, 4.2, 0.0);
      glRotatef(-2.0 * angle - 25.0, 0.0, 0.0, 1.0);
      glCallList(gear3);
    glPopMatrix();

    glPushMatrix(); /* JSS */
      glTranslatef(3.8, 4.1, 0.0);
      glRotatef(angle-0.75, 0.0, 0.0, 1.0);
      glCallList(gear4);
    glPopMatrix();

  glPopMatrix();
  drawText();
  glutSwapBuffers();

  Frames++;

  {
     GLint t = glutGet(GLUT_ELAPSED_TIME);
     if (t - T0 >= 5000) {
        GLfloat seconds = (t - T0) / 1000.0;
        GLfloat fps = Frames / seconds;
        printf("%d frames in %6.3f seconds = %6.3f FPS\n", Frames, seconds, fps);
        T0 = t;
        Frames = 0;
        if ((t >= 999.0 * autoexit) && (autoexit))
           exit(0);
     }
  }
} /* end draw function */

static void idle(void)
{
  angle += incAngle;
  glutPostRedisplay();
}

static void key(unsigned char k, int x, int y)
{
  switch (k) {
  case 'z':
    view_rotz += 5.0;
    break;
  case 'Z':
    view_rotz -= 5.0;
    break;
  case 'a':
    incAngle -= 0.25;
    break;
  case 'A':
    incAngle += 0.25;
    break;
  case 'W':
    background = 1;
    break;
  case 'B':
    background = 0;
    break;
  case 'q':
    exit(0);
    break;
  default:
    return;
  }
  glutPostRedisplay();
} /* end key function */

/* change view angle */
static void special(int k, int x, int y)
{
  switch (k) {
  case GLUT_KEY_UP: /* up arrow */
    view_rotx += 5.0;
    break;
  case GLUT_KEY_DOWN:
    view_rotx -= 5.0;
    break;
  case GLUT_KEY_LEFT: /* left arrow */
    view_roty += 5.0;
    break;
  case GLUT_KEY_RIGHT:
    view_roty -= 5.0;
    break;
  default:
    return;
  }
  glutPostRedisplay();
}

/* new window size or exposure */
static void reshape(int width, int height)
{
  GLfloat hw = (GLfloat)height / (GLfloat)width;

  glViewport(0, 0, (GLint)width, (GLint)height);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glFrustum(-1.0, 1.0, -hw, hw, 5.0, 60.0);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glTranslatef(0.0, 0.0, -50.0);
  winHeight = height;
  winWidth  = width;
} /* end reshape */

static void init(int argc, char *argv[])
{
  static GLfloat pos[4] = {5.0, 5.0, 10.0, 0.0};
  static GLfloat red[4] = {0.8, 0.1, 0.0, 1.0};
  static GLfloat green[4] = {0.0, 0.8, 0.2, 1.0};
  static GLfloat blue[4] = {0.2, 0.2, 1.0, 1.0};
  static GLfloat gray[4] = {0.5, 0.5, 0.5, 1.0}; /* JSS */
  GLint i;

  glLightfv(GL_LIGHT0, GL_POSITION, pos);
  glEnable(GL_CULL_FACE);
  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
  glEnable(GL_DEPTH_TEST);

  /* make the gears */
  gear1 = glGenLists(1);
  glNewList(gear1, GL_COMPILE);
  glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, red);
  gear(1.0, 4.0, 1.0, 20, 0.7);
  glEndList();

  gear2 = glGenLists(1);
  glNewList(gear2, GL_COMPILE);
  glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, green);
  gear(0.5, 2.0, 2.0, 10, 0.7);
  glEndList();

  gear3 = glGenLists(1);
  glNewList(gear3, GL_COMPILE);
  glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, blue);
  gear(1.3, 2.0, 0.5, 10, 0.7);
  glEndList();

  gear4 = glGenLists(1); /* JSS */
  glNewList(gear4, GL_COMPILE);
  glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, gray);
  gear(2.0, 4.0, 3.0, 20, 0.7);
  glEndList();


  glEnable(GL_NORMALIZE);

  for ( i=1; i<argc; i++ ) {
    if (strcmp(argv[i], "-info")==0) {
      printf("GL_RENDERER   = %s\n", (char *) glGetString(GL_RENDERER));
      printf("GL_VERSION    = %s\n", (char *) glGetString(GL_VERSION));
      printf("GL_VENDOR     = %s\n", (char *) glGetString(GL_VENDOR));
      printf("GL_EXTENSIONS = %s\n", (char *) glGetString(GL_EXTENSIONS));
    }
    else if ( strcmp(argv[i], "-exit")==0) {
      autoexit = 30;
      printf("Auto Exit after %i seconds.\n", autoexit );
    }
  }
} /* end init function */

static void visible(int vis)
{
  if (vis == GLUT_VISIBLE)
    glutIdleFunc(idle);
  else
    glutIdleFunc(NULL);
}

int main(int argc, char *argv[])
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);

  glutInitWindowPosition(0, 0);
  glutInitWindowSize(winHeight, winWidth);
  glutCreateWindow(argv[0]);
  init(argc, argv);

  glutDisplayFunc(draw);
  glutReshapeFunc(reshape);
  glutKeyboardFunc(key);
  glutSpecialFunc(special);
  glutVisibilityFunc(visible);

  glutMainLoop();
  return 0;
} /* end main function of gears4.c file */