Function OrbitPlot

xcharts1.cpp:2521–2573

// so its distance from the central body is on a logarithmic scale.

void OrbitPlot(real *pxp, real *pyp, real *pzp, real sz, int obj, PT3R *rgspc)
{
  real xp, yp, zp, xd, yd, zd, rDist;
  int objCenter;
  PT3R *spc;

  // Copy input parameters. Only care about Z-axis in 3D wireframe charts.
  xp = *pxp; yp = *pyp;
  zp = pzp != NULL ? *pzp : 0.0;

  // Tempoarily treat things orbiting planets as that planet's position.
  objCenter = ObjOrbit(obj);
  if (objCenter >= 0 && objCenter != oSun) {
    spc = rgspc + objCenter;
    xd = (xp - spc->x);
    yd = (yp - spc->y);
    zd = (zp - spc->z);
    xp = spc->x;
    yp = spc->y;
    zp = spc->z;
  }

  // Compute distance, determine ratio, and recompute coordinates.
  rDist = RLength3(xp, yp, zp);
  if (rDist < rSmall)
    return;
  rDist = (RLog(rDist / sz * 100.0 + 1.0) / rLog101) / (rDist / sz);
  xp *= rDist; yp *= rDist; zp *= rDist;

  // Scale things orbiting planets to be more distant from them.
  if (objCenter >= 0 && objCenter != oSun) {
    rDist = 1000.0 * (objCenter == oEar ? 1.0 : (objCenter == oMar ? 15.0 :
      (objCenter == oJup ? 0.9 : (objCenter == oSat ? 0.7 :
      (objCenter == oUra ? 4.0 : (objCenter == oNep ? 0.4 : 25.0))))));
#if FALSE
    // Modify radius with AstroExpression if one set.
    if (!us.fExpOff && FSzSet(us.szExpOrbit)) {
      ExpSetN(iLetterY, obj);
      ExpSetR(iLetterZ, rDist);
      ParseExpression(us.szExpOrbit);
      rDist = RExpGet(iLetterZ);
    }
#endif
    xp += xd * rDist;
    yp += yd * rDist;
    zp += zd * rDist;
  }

  // Copy back to input parameters.
  *pxp = xp; *pyp = yp;
  if (pzp != NULL)
    *pzp = zp;
}


// This is a subprocedure of XChartOrbit(). Append the current set of planet