Function DrawMapSquare

xcharts0.cpp:1781–1824

// squares should be nested a specified number of levels deep.

void DrawMapSquare(real lon1, real lat1, real lon2, real lat2,
  real lon3, real lat3, real lon4, real lat4,
  flag fGlobe, int nScl, CIRC *pcr, real deg, int nLevel, int grf)
{
  real x0, y0, x1, y1, x2, y2, x3, y3, x4, y4;

  // Recursive case: Draw four smaller squares composing this square.
  if (nLevel > 0) {
    // Square's center is the midpoint of the midpoints of opposite corners.
    SphRatio(lon1, lat1, lon3, lat3, 0.5, &x1, &y1);
    SphRatio(lon2, lat2, lon4, lat4, 0.5, &x2, &y2);
    SphRatio(x1, y1, x2, y2, 0.5, &x0, &y0);

    SphRatio(lon1, lat1, lon2, lat2, 0.5, &x1, &y1);
    SphRatio(lon2, lat2, lon3, lat3, 0.5, &x2, &y2);
    SphRatio(lon3, lat3, lon4, lat4, 0.5, &x3, &y3);
    SphRatio(lon4, lat4, lon1, lat1, 0.5, &x4, &y4);
    DrawMapSquare(lon1, lat1, x1, y1, x0, y0, x4, y4, fGlobe, nScl, pcr, deg,
      nLevel-1, (grf | 2) & 11);
    DrawMapSquare(x1, y1, lon2, lat2, x2, y2, x0, y0, fGlobe, nScl, pcr, deg,
      nLevel-1, (grf | 4) &  7);
    DrawMapSquare(x0, y0, x2, y2, lon3, lat3, x3, y3, fGlobe, nScl, pcr, deg,
      nLevel-1, (grf | 8) & 14);
    DrawMapSquare(x4, y4, x0, y0, x3, y3, lon4, lat4, fGlobe, nScl, pcr, deg,
      nLevel-1, (grf | 1) & 13);
    return;
  }

  // Base case: Draw the four sides of the square.
  if (!fGlobe) {
    lon1 = Mod(lon1 + deg);
    lon2 = Mod(lon2 + deg);
    lon3 = Mod(lon3 + deg);
    lon4 = Mod(lon4 + deg);
  }
  if (grf & 1)
    DrawMapLine(lon1, lat1, lon2, lat2, fGlobe, nScl, pcr, deg);
  if (grf & 2)
    DrawMapLine(lon2, lat2, lon3, lat3, fGlobe, nScl, pcr, deg);
  if (grf & 4)
    DrawMapLine(lon3, lat3, lon4, lat4, fGlobe, nScl, pcr, deg);
  if (grf & 8)
    DrawMapLine(lon4, lat4, lon1, lat1, fGlobe, nScl, pcr, deg);
}


// Draw a grid of triangles or squares over the surface of the planet.