depthcue.c Example C Language Program

/* depthcue.c Example C Language Program 
 *
 * Draws a depthcue'd 3-d wireframe cube with lots of 
 * little points inside. Moving the mouse rotates the
 * cube.
 * NEAR and FAR (Z) clipplanes map to z values of
 * getgdesc(GD_ZMIN) and getgdesc(GD_ZMAX) respectively.
 * Points near NEAR are the brightest, those near FAR are
 * the dimmest. Give two hexadecimal values on the command
 * line to specify which zvalues are mapped to bright
 * and dark.
 *
 * Press the middle mouse to quit.
 */

#include <gl/gl.h>
#include <gl/device.h>
#include <math.h>

#define CUBE 9531

float hrand();

/*Hold the colormap values*/
static short *CarrayR, *CarrayG, *CarrayB;

main (argc,argv)
int argc;
char **argv;
{
  int val, i;
  long near, far,           /*Z buffer and depth cueing*/
     nearest, farthest;     /*information*/
  float inc, c;
  short lo_end=128,         /*Low/High index of the colormap*/ 
     hi_end=255;            /*Used for the depth cueing*/

  prefposition(200, 600, 200, 600);
  winopen("depthcue");
  winconstraints();
  doublebuffer();
  gconfig();

  /*Find out the nearest and farthest values of the z mapping*/
  nearest   = getgdesc(GD_ZMIN);
  farthest  = getgdesc(GD_ZMAX);

  if (argc == 5) {
    near = strtol(argv[1], (char **) NULL, 0);
    far = strtol(argv[2], (char **) NULL, 0);
    lo_end = strtol(argv[3], (char **) NULL, 0);
    hi_end = strtol(argv[4], (char **) NULL, 0);

  }
  else if (argc == 3)  {
    near = strtol(argv[1], (char **) NULL, 0);
    far = strtol(argv[2], (char **) NULL, 0);
  }
  else {
    near = nearest;
    far  = farthest;
  }

  if (near < nearest)  near=nearest; /*Clamp to adapters constraints*/
  if (far  > farthest) far=farthest;

  reshapeviewport();
  perspective(600, 1.0, 350.0, 1400.0);
  lookat(0.0, 0.0, 700.0, 0.0, 0.0, 0.0, 0);
  qdevice(KEYBD);    
  makeobj(CUBE);              /* generate a bunch of random points */
  for (i = 0; i < 100; i++)
    pnt(hrand(-200.0,200.0), hrand(-200.0,200.0), 
        hrand(-200.0,200.0)); /* and a cube */
  movei(-200, -200, -200);
  drawi( 200, -200, -200);
  drawi( 200,  200, -200);
  drawi(-200,  200, -200);
  drawi(-200, -200, -200);
  drawi(-200, -200,  200);
  drawi(-200,  200,  200);
  drawi(-200,  200, -200);
  movei(-200,  200,  200);
  drawi( 200,  200,  200);
  drawi( 200, -200,  200);
  drawi(-200, -200,  200);
  movei( 200,  200,  200);
  drawi( 200,  200, -200);
  movei( 200, -200, -200);
  drawi( 200, -200,  200);
  closeobj();

  /*Save the current colormap so it can be reset when the program ends*/
  save_cmap(lo_end,hi_end); 

  /* load the color map with a cyan ramp */
  /* starting at lo_end and going to hi_end inclusively */

  inc = 255.0/((float)(hi_end-lo_end));
  c = 0.0;
  for (i = lo_end; i <= hi_end; i++)
    {
      c += inc;
      mapcolor(i, 0,(Int16) c, (Int16) c);
    }

  /*Print out the information about the color and z buffer*/
  printf (" near    = %ld, far      = %ld \n", near, far);
  printf (" nearest = %ld, farthest = %ld \n", nearest, farthest);
  printf (" low colormap = %d, high colormap = %d\n", lo_end, hi_end);
  printf (" number of colors in ramp = %d \n", 1+hi_end-lo_end);

  /* Set the range of z values that will be stored in the  */
  /* bitplanes.  The percentage takes care of the error    */
  /* accumulation that occurs when the farthest limits are */
  /* used.                                                 */
  lsetdepth((long)(near*0.98), (long)(far*0.98));

  /* set up the mapping of z values to color map           */
  /* indexes: z value nearest is mapped to index lo_end    */
  /* and z value farthest is mapped to index hi_end        */
  lshaderange(lo_end,hi_end,nearest,farthest);

  /* turn on depthcue mode:  the color index of each       */
  /* pixel in points and lines is determined from the      */
  /* z value of the pixel                                  */
  depthcue(TRUE);

  /* until a key is pressed, rotate cube according to      */
  /* movement of the mouse                                 */
  while (!getbutton(MIDDLEMOUSE)) {
    pushmatrix();
    rotate(3*getvaluator(MOUSEY), 'x');
    rotate(3*getvaluator(MOUSEX), 'y');
    color(BLACK);
    clear();
    callobj(CUBE);
    popmatrix();
    swapbuffers();
  }

  /*Restore the colormap*/
  restore_cmap(lo_end,hi_end);
  /*Exit gracefully*/
  gexit();
  exit(1);
}

/* this routine returns random numbers in the            */
/* specified range                                       */
float hrand(low,high)
float low,high;
{
  float val;    
  val = ((float)( (short)rand() & 0xffff)) / ((float)0xffff);
  return( (2.0 * val * (high-low)) + low);
}

/*This saves the colormap*/
save_cmap(lo_end,hi_end)
short lo_end,hi_end;
{

  CarrayR = calloc (lo_end+hi_end,sizeof(short));
  CarrayG = calloc (lo_end+hi_end,sizeof(short));
  CarrayB = calloc (lo_end+hi_end,sizeof(short));

  getmcolors ((Int16 const)lo_end,(Int16 const)hi_end,
     CarrayR, CarrayG, CarrayB);
}

/*This restores the colormap*/
restore_cmap(lo_end,hi_end)
short lo_end,hi_end;
{
  mapcolors ((Int16 const)lo_end,(Int16 const)hi_end,
     CarrayR, CarrayG, CarrayB);
}

/*Changes
    -  Put constants in the program for the colormap creation
    -  This program accept 2 arguments that are the nearest and
       farthest z values which are used for the depth cueing.
       This program called: lshaderange(128,255,-0x40000,0x3FFFFF);
       now:    lshaderange(lo_end,hi_end,nearest,farthest);
    -  Used a define for the object number (called CUBE)
    -  Save/restore the colormap
    -  The defaults of the near and far z mappings are no longer
       hard coded  ( near = -0x400000; far = 0x3fffff;), but are
       initialized with getgdesc.  Also the near and far mappings
       are clamped to there min and max values respectively.
*/

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