protovis_dymaxion.js

/************************************************************************/
/* NOTE: in C, array indexing starts with element zero(0).  I choose   */
/*       to start my array indexing with elemennt one(1) so all arrays */
/*       are defined one element longer than they need to be.           */
/************************************************************************/

/************************************************************************/
/* global variables accessable to all procedures                        */
/************************************************************************/

const SQRT_3  = Math.sqrt(3);
const SQRT_5  = Math.sqrt(5);
const SQRT_8  = Math.sqrt(8);
const SQRT_10 = Math.sqrt(10);
const SQRT_15 = Math.sqrt(15);

var v_x = new Array(13);
var v_y = new Array(13);
var v_z = new Array(13);
var center_x = new Array(21);
var center_y = new Array(21);
var center_z = new Array(21);
var garc, gt, gdve, gel;


/****************************************/
/*      function definitions            */
/****************************************/
var last_lng = 100000;
var last_lat = 100000;
var last_point;
function convert_s_t_p_cache(lng, lat) {
  if(last_lng == lng && last_lat == lat) {
    return last_point;
  } else {
    last_lng = lng;
    last_lat = lat;
    last_point = convert_s_t_p(lng, lat);
    return last_point;
  }
}

function convert_s_t_p(lng, lat) {
  /***********************************************************/
  /* This is the main control procedure.                     */
  /***********************************************************/

  /* Convert the given(long.,lat.) coordinate into spherical */
  /* polar coordinates(r, theta, phi) with radius=1.         */
  /* Angles are given in radians, NOT degrees.               */

  // var sc = conv_ll_t_sc(lng, lat);
  var sc = recalc_radians(lng,lat);
  
  // var sc = new Object();
  // var π = Math.PI;
  // sc.theta = (π/2) - lat;
  // sc.phi = lng;


  /* convert the spherical polar coordinates into cartesian   */
  /* (x, y, z) coordinates.                                   */

  var h = s_to_c(sc.theta, sc.phi);

  /* determine which of the 20 spherical icosahedron triangles */
  /* the given point is in and the LCD triangle.               */

  var info = s_tri_info(h.x, h.y, h.z);

  /* Determine the corresponding Fuller map plane(x, y) point */
  return dymax_point(info.tri, info.hlcd, h.x, h.y, h.z);
}


function convert_i_t_p(i, t) {
  var x = 0;
  var y = 0;
  var z = 0;
  
  // We need to 'nudge' the point a little bit into the triangle
  // Hence we do a weighted average with point i having a massive weight
  for(var j = 0; j < 3; j++) {
    if(t[j] == i) {
      x += v_x[i] * 0.9999;
      y += v_y[i] * 0.9999;
      z += v_z[i] * 0.9999;
    } else {
      x += v_x[t[j]] * 0.00005;
      y += v_y[t[j]] * 0.00005;
      z += v_z[t[j]] * 0.00005;
    }
  }
  
  var info = s_tri_info(x, y, z);
  /* Determine the corresponding Fuller map plane(x, y) point */

  return dymax_point(info.tri, info.hlcd, x, y, z);
}


function conv_ll_t_sc(lng, lat) {
  /* convert(long., lat.) point into spherical polar coordinates */
  /* with r=radius=1.  Angles are given in radians.               */
  var sc = new Object();
  var h_theta, h_phi;
 
  h_theta = 90.0 - lat ;
  h_phi = lng;
  if(lng < 0.0) {h_phi = lng + 360.0;}
  sc.theta = radians(h_theta);
  sc.phi = radians(h_phi);

  return sc;
} /* end conv_ll_t_sc */

function recalc_radians(λ, φ) {
  /* convert(long., lat.) point into spherical polar coordinates */
  /* with r=radius=1.  Angles are given in radians.               */
  var sc = new Object();
  sc.theta = (Math.PI/2) - φ;
  sc.phi = λ;

  return sc;
} /* end conv_ll_t_sc */

function radians(degrees) {
    /* convert angles in degrees into angles in radians */
    return(Math.PI * degrees / 180);
} /* end of radians function */


function init_stuff() {
   /* initializes the global variables which includes the */
   /* vertix coordinates and mid-face coordinates.        */

   var i, hold_x, hold_y, hold_z, magn;
   var theta, phi;

   /* Cartesian coordinates for the 12 vertices of icosahedron */

   v_x[1] =    0.420152426708710003;
   v_y[1] =    0.078145249402782959;
   v_z[1] =    0.904082550615019298;
   v_x[2] =    0.995009439436241649;
   v_y[2] =   -0.091347795276427931;
   v_z[2] =    0.040147175877166645;
   v_x[3] =    0.518836730327364437;
   v_y[3] =    0.835420380378235850;
   v_z[3] =    0.181331837557262454;
   v_x[4] =   -0.414682225320335218;
   v_y[4] =    0.655962405434800777;
   v_z[4] =    0.630675807891475371;
   v_x[5] =   -0.515455959944041808;
   v_y[5] =   -0.381716898287133011;
   v_z[5] =    0.767200992517747538;
   v_x[6] =    0.355781402532944713;
   v_y[6] =   -0.843580002466178147;
   v_z[6] =    0.402234226602925571;
   v_x[7] =    0.414682225320335218;
   v_y[7] =   -0.655962405434800777;
   v_z[7] =   -0.630675807891475371;
   v_x[8] =    0.515455959944041808;
   v_y[8] =    0.381716898287133011;
   v_z[8] =   -0.767200992517747538;
   v_x[9] =   -0.355781402532944713;
   v_y[9] =    0.843580002466178147;
   v_z[9] =   -0.402234226602925571;
   v_x[10] =  -0.995009439436241649;
   v_y[10] =   0.091347795276427931;
   v_z[10] =  -0.040147175877166645;
   v_x[11] =  -0.518836730327364437;
   v_y[11] =  -0.835420380378235850;
   v_z[11] =  -0.181331837557262454;
   v_x[12] =  -0.420152426708710003;
   v_y[12] =  -0.078145249402782959;
   v_z[12] =  -0.904082550615019298;

   /* now calculate mid face coordinates             */

   hold_x = (v_x[1] + v_x[2] + v_x[3]) / 3.0 ;
   hold_y = (v_y[1] + v_y[2] + v_y[3]) / 3.0 ;
   hold_z = (v_z[1] + v_z[2] + v_z[3]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[1] = hold_x / magn;
   center_y[1] = hold_y / magn;
   center_z[1] = hold_z / magn;

   hold_x = (v_x[1] + v_x[3] + v_x[4]) / 3.0 ;
   hold_y = (v_y[1] + v_y[3] + v_y[4]) / 3.0 ;
   hold_z = (v_z[1] + v_z[3] + v_z[4]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[2] = hold_x / magn;
   center_y[2] = hold_y / magn;
   center_z[2] = hold_z / magn;

   hold_x = (v_x[1] + v_x[4] + v_x[5]) / 3.0 ;
   hold_y = (v_y[1] + v_y[4] + v_y[5]) / 3.0 ;
   hold_z = (v_z[1] + v_z[4] + v_z[5]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[3] = hold_x / magn;
   center_y[3] = hold_y / magn;
   center_z[3] = hold_z / magn;

   hold_x = (v_x[1] + v_x[5] + v_x[6]) / 3.0 ;
   hold_y = (v_y[1] + v_y[5] + v_y[6]) / 3.0 ;
   hold_z = (v_z[1] + v_z[5] + v_z[6]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[4] = hold_x / magn;
   center_y[4] = hold_y / magn;
   center_z[4] = hold_z / magn;

   hold_x = (v_x[1] + v_x[2] + v_x[6]) / 3.0 ;
   hold_y = (v_y[1] + v_y[2] + v_y[6]) / 3.0 ;
   hold_z = (v_z[1] + v_z[2] + v_z[6]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[5] = hold_x / magn;
   center_y[5] = hold_y / magn;
   center_z[5] = hold_z / magn;

   hold_x = (v_x[2] + v_x[3] + v_x[8]) / 3.0 ;
   hold_y = (v_y[2] + v_y[3] + v_y[8]) / 3.0 ;
   hold_z = (v_z[2] + v_z[3] + v_z[8]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[6] = hold_x / magn;
   center_y[6] = hold_y / magn;
   center_z[6] = hold_z / magn;

   hold_x = (v_x[8] + v_x[3] + v_x[9]) / 3.0 ;
   hold_y = (v_y[8] + v_y[3] + v_y[9]) / 3.0 ;
   hold_z = (v_z[8] + v_z[3] + v_z[9]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[7] = hold_x / magn;
   center_y[7] = hold_y / magn;
   center_z[7] = hold_z / magn;

   hold_x = (v_x[9] + v_x[3] + v_x[4]) / 3.0 ;
   hold_y = (v_y[9] + v_y[3] + v_y[4]) / 3.0 ;
   hold_z = (v_z[9] + v_z[3] + v_z[4]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[8] = hold_x / magn;
   center_y[8] = hold_y / magn;
   center_z[8] = hold_z / magn;

   hold_x = (v_x[10] + v_x[9] + v_x[4]) / 3.0 ;
   hold_y = (v_y[10] + v_y[9] + v_y[4]) / 3.0 ;
   hold_z = (v_z[10] + v_z[9] + v_z[4]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[9] = hold_x / magn;
   center_y[9] = hold_y / magn;
   center_z[9] = hold_z / magn;

   hold_x = (v_x[5] + v_x[10] + v_x[4]) / 3.0 ;
   hold_y = (v_y[5] + v_y[10] + v_y[4]) / 3.0 ;
   hold_z = (v_z[5] + v_z[10] + v_z[4]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[10] = hold_x / magn;
   center_y[10] = hold_y / magn;
   center_z[10] = hold_z / magn;

   hold_x = (v_x[5] + v_x[11] + v_x[10]) / 3.0 ;
   hold_y = (v_y[5] + v_y[11] + v_y[10]) / 3.0 ;
   hold_z = (v_z[5] + v_z[11] + v_z[10]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[11] = hold_x / magn;
   center_y[11] = hold_y / magn;
   center_z[11] = hold_z / magn;

   hold_x = (v_x[5] + v_x[6] + v_x[11]) / 3.0 ;
   hold_y = (v_y[5] + v_y[6] + v_y[11]) / 3.0 ;
   hold_z = (v_z[5] + v_z[6] + v_z[11]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[12] = hold_x / magn;
   center_y[12] = hold_y / magn;
   center_z[12] = hold_z / magn;

   hold_x = (v_x[11] + v_x[6] + v_x[7]) / 3.0 ;
   hold_y = (v_y[11] + v_y[6] + v_y[7]) / 3.0 ;
   hold_z = (v_z[11] + v_z[6] + v_z[7]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[13] = hold_x / magn;
   center_y[13] = hold_y / magn;
   center_z[13] = hold_z / magn;

   hold_x = (v_x[7] + v_x[6] + v_x[2]) / 3.0 ;
   hold_y = (v_y[7] + v_y[6] + v_y[2]) / 3.0 ;
   hold_z = (v_z[7] + v_z[6] + v_z[2]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[14] = hold_x / magn;
   center_y[14] = hold_y / magn;
   center_z[14] = hold_z / magn;

   hold_x = (v_x[8] + v_x[7] + v_x[2]) / 3.0 ;
   hold_y = (v_y[8] + v_y[7] + v_y[2]) / 3.0 ;
   hold_z = (v_z[8] + v_z[7] + v_z[2]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[15] = hold_x / magn;
   center_y[15] = hold_y / magn;
   center_z[15] = hold_z / magn;

   hold_x = (v_x[12] + v_x[9] + v_x[8]) / 3.0 ;
   hold_y = (v_y[12] + v_y[9] + v_y[8]) / 3.0 ;
   hold_z = (v_z[12] + v_z[9] + v_z[8]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[16] = hold_x / magn;
   center_y[16] = hold_y / magn;
   center_z[16] = hold_z / magn;

   hold_x = (v_x[12] + v_x[9] + v_x[10]) / 3.0 ;
   hold_y = (v_y[12] + v_y[9] + v_y[10]) / 3.0 ;
   hold_z = (v_z[12] + v_z[9] + v_z[10]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[17] = hold_x / magn;
   center_y[17] = hold_y / magn;
   center_z[17] = hold_z / magn;

   hold_x = (v_x[12] + v_x[11] + v_x[10]) / 3.0 ;
   hold_y = (v_y[12] + v_y[11] + v_y[10]) / 3.0 ;
   hold_z = (v_z[12] + v_z[11] + v_z[10]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[18] = hold_x / magn;
   center_y[18] = hold_y / magn;
   center_z[18] = hold_z / magn;

   hold_x = (v_x[12] + v_x[11] + v_x[7]) / 3.0 ;
   hold_y = (v_y[12] + v_y[11] + v_y[7]) / 3.0 ;
   hold_z = (v_z[12] + v_z[11] + v_z[7]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[19] = hold_x / magn;
   center_y[19] = hold_y / magn;
   center_z[19] = hold_z / magn;

   hold_x = (v_x[12] + v_x[8] + v_x[7]) / 3.0 ;
   hold_y = (v_y[12] + v_y[8] + v_y[7]) / 3.0 ;
   hold_z = (v_z[12] + v_z[8] + v_z[7]) / 3.0 ;
   magn = Math.sqrt(hold_x * hold_x + hold_y * hold_y + hold_z * hold_z);
   center_x[20] = hold_x / magn;
   center_y[20] = hold_y / magn;
   center_z[20] = hold_z / magn;

   garc = 2.0 * Math.asin( Math.sqrt( 5 - SQRT_5) / SQRT_10 );
   gt = garc / 2.0;

   gdve = Math.sqrt( 3 + SQRT_5 ) / Math.sqrt( 5 + SQRT_5 );
   gel = SQRT_8 / Math.sqrt(5 + SQRT_5);
} /* end of int_stuff procedure */


function s_to_c(theta, phi) {
    /* Covert spherical polar coordinates to cartesian coordinates. */
    /* The angles are given in radians.                             */
    var c = new Object();
    c.x = Math.sin(theta) * Math.cos(phi);
    c.y = Math.sin(theta) * Math.sin(phi);
    c.z = Math.cos(theta);
    
    return c;
 } /* end s_to_c */


function c_to_s(x, y, z) {
    /* convert cartesian coordinates into spherical polar coordinates. */
    /* The angles are given in radians.                                */
    var s = new Object();
    var a;

    if(x>0.0 && y>0.0) {a = radians(0.0);}
    if(x<0.0 && y>0.0) {a = radians(180.0);}
    if(x<0.0 && y<0.0) {a = radians(180.0);}
    if(x>0.0 && y<0.0) {a = radians(360.0);}
    s.lat = Math.acos(z);
    if(x==0.0 && y>0.0) {s.lng = radians(90.0);}
    if(x==0.0 && y<0.0) {s.lng = radians(270.0);}
    if(x>0.0 && y==0.0) {s.lng = radians(0.0);}
    if(x<0.0 && y==0.0) {s.lng = radians(180.0);}
    if(x!=0.0 && y!=0.0){s.lng = Math.atan(y/x) + a;}
    
    return s;
} /* end c_to_s */


function s_tri_info(x, y, z) {
  /* Determine which triangle and LCD triangle the point is in. */

  var h_dist1, h_dist2, h_dist3, h1, h2, h3; // double
  var i, h_tri, h_lcd ;  //int
  var v1, v2, v3;       // int
  
  var info = new Object();

  h_tri = 0;
  h_dist1 = 9999.0;

  /* Which triangle face center is the closest to the given point */
  /* is the triangle in which the given point is in.              */

  for(i = 1; i <=20; i = i + 1) {
     h1 = center_x[i] - x;
     h2 = center_y[i] - y;
     h3 = center_z[i] - z;
     h_dist2 = Math.sqrt(h1 * h1 + h2 * h2 + h3 * h3);
     if(h_dist2 < h_dist1) {
        h_tri = i;
        h_dist1 = h_dist2;
      } /* end the if statement */
   }  /* end the for statement */

   info.tri = h_tri;

   /* Now the LCD triangle is determined. */

   switch(h_tri)
   {
    case 1:  v1 =  1; v2 =  3; v3 =  2; break;
    case 2:  v1 =  1; v2 =  4; v3 =  3; break;
    case 3:  v1 =  1; v2 =  5; v3 =  4; break;
    case 4:  v1 =  1; v2 =  6; v3 =  5; break;
    case 5:  v1 =  1; v2 =  2; v3 =  6; break;
    case 6:  v1 =  2; v2 =  3; v3 =  8; break;
    case 7:  v1 =  3; v2 =  9; v3 =  8; break;
    case 8:  v1 =  3; v2 =  4; v3 =  9; break;
    case 9:  v1 =  4; v2 = 10; v3 =  9; break;
    case 10: v1 =  4; v2 =  5; v3 = 10; break;
    case 11: v1 =  5; v2 = 11; v3 = 10; break;
    case 12: v1 =  5; v2 =  6; v3 = 11; break;
    case 13: v1 =  6; v2 =  7; v3 = 11; break;
    case 14: v1 =  2; v2 =  7; v3 =  6; break;
    case 15: v1 =  2; v2 =  8; v3 =  7; break;
    case 16: v1 =  8; v2 =  9; v3 = 12; break;
    case 17: v1 =  9; v2 = 10; v3 = 12; break;
    case 18: v1 = 10; v2 = 11; v3 = 12; break;
    case 19: v1 = 11; v2 =  7; v3 = 12; break;
    case 20: v1 =  8; v2 = 12; v3 =  7; break;
   } /* end of switch statement */

   h1 = x - v_x[v1];
   h2 = y - v_y[v1];
   h3 = z - v_z[v1];
   h_dist1 = Math.sqrt(h1 * h1 + h2 * h2 + h3 * h3);

   h1 = x - v_x[v2];
   h2 = y - v_y[v2];
   h3 = z - v_z[v2];
   h_dist2 = Math.sqrt(h1 * h1 + h2 * h2 + h3 * h3);

   h1 = x - v_x[v3];
   h2 = y - v_y[v3];
   h3 = z - v_z[v3];
   h_dist3 = Math.sqrt(h1 * h1 + h2 * h2 + h3 * h3);

   if( (h_dist1 <= h_dist2) && (h_dist2 <= h_dist3) ) {h_lcd = 1; }
   if( (h_dist1 <= h_dist3) && (h_dist3 <= h_dist2) ) {h_lcd = 6; }
   if( (h_dist2 <= h_dist1) && (h_dist1 <= h_dist3) ) {h_lcd = 2; }
   if( (h_dist2 <= h_dist3) && (h_dist3 <= h_dist1) ) {h_lcd = 3; }
   if( (h_dist3 <= h_dist1) && (h_dist1 <= h_dist2) ) {h_lcd = 5; }
   if( (h_dist3 <= h_dist2) && (h_dist2 <= h_dist1) ) {h_lcd = 4; }

   info.hlcd = h_lcd;

   return info;
} /* end s_tri_info */


function dymax_point(tri, lcd, x, y, z) {
  var axis, v1;  // int
  var h;

  var gs; // double
  var gx, gy, gz, ga1,ga2,ga3,ga1p,ga2p,ga3p,gxp,gyp,gzp; // double

  /* In order to rotate the given point into the template spherical */
  /* triangle, we need the spherical polar coordinates of the center */
  /* of the face and one of the face vertices. So set up which vertex */
  /* to use.                                                          */

   switch(tri)
   {
    case 1:  v1 =  1;  break;
    case 2:  v1 =  1;  break;
    case 3:  v1 =  1;  break;
    case 4:  v1 =  1;  break;
    case 5:  v1 =  1;  break;
    case 6:  v1 =  2;  break;
    case 7:  v1 =  3;  break;
    case 8:  v1 =  3;  break;
    case 9:  v1 =  4;  break;
    case 10: v1 =  4;  break;
    case 11: v1 =  5;  break;
    case 12: v1 =  5;  break;
    case 13: v1 =  6;  break;
    case 14: v1 =  2;  break;
    case 15: v1 =  2;  break;
    case 16: v1 =  8;  break;
    case 17: v1 =  9;  break;
    case 18: v1 = 10;  break;
    case 19: v1 = 11;  break;
    case 20: v1 =  8;  break;
   } /* end of switch statement */

   var h0 = new Object();
   h0.x = x;
   h0.y = y;
   h0.z = z;

   var h1 = new Object();
   h1.x = v_x[v1];
   h1.y = v_y[v1];
   h1.z = v_z[v1];

   h = c_to_s(center_x[tri], center_y[tri], center_z[tri]);

   axis = 3;
   rotate3d(axis,h.lng,h0);
   rotate3d(axis,h.lng,h1);

   axis = 2;
   rotate3d(axis,h.lat,h0);
   rotate3d(axis,h.lat,h1);

   h = c_to_s(h1.x,h1.y,h1.z);
   h.lng = h.lng - radians(90.0);

   axis = 3;
   rotate3d(axis,h.lng,h0);

   /* exact transformation equations */

   gz = Math.sqrt(1 - h0.x * h0.x - h0.y * h0.y);
   gs = Math.sqrt( 5 + 2 * SQRT_5 ) / ( gz * SQRT_15 );

   gxp = h0.x * gs ;
   gyp = h0.y * gs ;

   ga1p = 2.0 * gyp / SQRT_3 + (gel / 3.0) ;
   ga2p = gxp - (gyp / SQRT_3) +  (gel / 3.0) ;
   ga3p = (gel / 3.0) - gxp - (gyp / SQRT_3);

   ga1 = gt + Math.atan( (ga1p - 0.5 * gel) / gdve);
   ga2 = gt + Math.atan( (ga2p - 0.5 * gel) / gdve);
   ga3 = gt + Math.atan( (ga3p - 0.5 * gel) / gdve);

   gx = 0.5 * (ga2 - ga3) ;

   gy = (1.0 / (2.0 * SQRT_3) ) * (2 * ga1 - ga2 - ga3);

   /* Re-scale so plane triangle edge length is 1. */

   var pt = new Object();
   pt.x = gx / garc;
   pt.y = gy / garc;

  /* rotate and translate to correct position          */
  var point2d = new Object();
  
  switch(tri)
   {
     case  1: rotate2d(240.0,pt);
          point2d.x = pt.x + 2.0; point2d.y = pt.y + 7.0 / (2.0 * SQRT_3) ; break;
     case  2: rotate2d(300.0, pt); point2d.x = pt.x + 2.0;
              point2d.y = pt.y + 5.0 / (2.0 * SQRT_3) ; break;
     case  3: rotate2d(0.0, pt);
             point2d.x = pt.x + 2.5; point2d.y = pt.y + 2.0 / SQRT_3; break;
     case  4: rotate2d(60.0, pt);
              point2d.x = pt.x + 3.0; point2d.y = pt.y + 5.0 / (2.0 * SQRT_3) ; break;
     case  5: rotate2d(180.0, pt);
          point2d.x = pt.x + 2.5; point2d.y = pt.y + 4.0 * SQRT_3 / 3.0; break;
     case  6: rotate2d(300.0, pt);
              point2d.x = pt.x + 1.5; point2d.y = pt.y + 4.0 * SQRT_3 / 3.0; break;
     case  7: rotate2d(300.0, pt);
              point2d.x = pt.x + 1.0; point2d.y = pt.y + 5.0 / (2.0 * SQRT_3) ; break;
     case  8: rotate2d(0.0, pt);
              point2d.x = pt.x + 1.5; point2d.y = pt.y + 2.0 / SQRT_3; break;
     case  9: if(lcd > 2)
          {
          rotate2d(300.0, pt);
          point2d.x = pt.x + 1.5; point2d.y = pt.y + 1.0 / SQRT_3;
          }
          else
          {
          rotate2d(0.0, pt);
          point2d.x = pt.x + 2.0; point2d.y = pt.y + 1.0 / (2.0 * SQRT_3);
          }
          break;

     case 10: rotate2d(60.0, pt);
              point2d.x = pt.x + 2.5; point2d.y = pt.y + 1.0 / SQRT_3; break;
     case 11: rotate2d(60.0, pt);
              point2d.x = pt.x + 3.5; point2d.y = pt.y + 1.0 / SQRT_3; break;
     case 12: rotate2d(120.0, pt);
              point2d.x = pt.x + 3.5; point2d.y = pt.y + 2.0 / SQRT_3; break;
     case 13: rotate2d(60.0, pt);
              point2d.x = pt.x + 4.0; point2d.y = pt.y + 5.0 / (2.0 * SQRT_3); break;
     case 14: rotate2d(0.0, pt);
          point2d.x = pt.x + 4.0; point2d.y = pt.y + 7.0 / (2.0 * SQRT_3) ; break;
     case 15: rotate2d(0.0, pt);
          point2d.x = pt.x + 5.0; point2d.y = pt.y + 7.0 / (2.0 * SQRT_3) ; break;
     case 16: if(lcd < 4)
          {
        rotate2d(60.0, pt);
        point2d.x = pt.x + 0.5; point2d.y = pt.y + 1.0 / SQRT_3;
           }
           else
           {
        rotate2d(0.0, pt);
        point2d.x = pt.x + 5.5; point2d.y = pt.y + 2.0 / SQRT_3;
           }
           break;
     case 17: rotate2d(0.0, pt);
          point2d.x = pt.x + 1.0; point2d.y = pt.y + 1.0 / (2.0 * SQRT_3); break;
     case 18: rotate2d(120.0, pt);
              point2d.x = pt.x + 4.0; point2d.y = pt.y + 1.0 / (2.0 * SQRT_3); break;
     case 19: rotate2d(120.0, pt);
              point2d.x = pt.x + 4.5; point2d.y = pt.y + 2.0 / SQRT_3; break;
     case 20: rotate2d(300.0, pt);
              point2d.x = pt.x + 5.0; point2d.y = pt.y + 5.0 / (2.0 * SQRT_3); break;

   } /* end switch statement */
   
   return point2d;
} /* end of dymax_point */


function rotate2d(angle, point2d) {
  /* Rotate the point to correct orientation in XY-plane. */

  var ha, hx, hy; // double

  ha = radians(angle);
  hx = point2d.x;
  hy = point2d.y;
  point2d.x = hx * Math.cos(ha) - hy * Math.sin(ha);
  point2d.y = hx * Math.sin(ha) + hy * Math.cos(ha);
  
  return point2d;
} /* end rotate procedure */


function rotate3d(axis, alpha, point3d) {
  /* Rotate a 3-D point about the specified axis.         */

  var a = point3d.x;
  var b = point3d.y;
  var c = point3d.z;
  
  if(axis == 1) {
    point3d.y = b * Math.cos(alpha) + c * Math.sin(alpha);
    point3d.z = c * Math.cos(alpha) - b * Math.sin(alpha);
  }

  if(axis == 2) {
    point3d.x = a * Math.cos(alpha) - c * Math.sin(alpha);
    point3d.z = a * Math.sin(alpha) + c * Math.cos(alpha);
  }

  if(axis == 3) {
    point3d.x = a * Math.cos(alpha) + b * Math.sin(alpha);
    point3d.y = b * Math.cos(alpha) - a * Math.sin(alpha);
  }
  
  return point3d;
} /* end of r2 */


init_stuff();