#!/usr/bin/env python  exaggeration = 20 header       = ('Mars %s-times-exaggerated elevation model by CMG Lee using MGS MOLA data.'                 % (exaggeration)) path_png_alt = 'mars_elevation.png' ## 1-channel equirectangular PNG luma_datum   = 42                   ## of 0-255 intensity levels radius_datum = 3389.5               ## in km f_wgs84      = 1 - 3376.2 / 3396.2  ## WGS84 flattening factor km_per_luma  = 0.155 * exaggeration ## found from Olympus Mons scale        = 1e-2                 ## overall scale of model lat_offset   = 1.0 / 8              ## rotation around planet axis in revolutions n_division   = 200                  ## each cubic face divided into n_division^2 squares  class Png:  def __init__(self, path):   (self.width, self.height, self.pixels, self.metadatas) = png.Reader(path).read_flat()  def __str__(self): return str((self.width, self.height, len(self.pixels), self.metadatas))  import time, re, math, struct, png time.start = time.time() def log(string): print('%6.3fs\t%s' % (time.time() - time.start, string)) def fmt(string): ## string.format(**vars()) using tags {expression!format} by CMG Lee  def f(tag): i_sep = tag.rfind('!'); return (re.sub('\.0+$', '', str(eval(tag[1:-1])))   if (i_sep < 0) else ('{:%s}' % tag[i_sep + 1:-1]).format(eval(tag[1:i_sep])))  return (re.sub(r'(?<!{){[^{}]+}', lambda m:f(m.group()), string)          .replace('{{', '{').replace('}}', '}')) def append(obj, string): return obj.append(fmt(string)) def tabbify(cellss, separator='|'):  cellpadss = [list(rows) + [''] * (len(max(cellss, key=len)) - len(rows)) for rows in cellss]  fmts = ['%%%ds' % (max([len(str(cell)) for cell in cols])) for cols in zip(*cellpadss)]  return '\n'.join([separator.join(fmts) % tuple(rows) for rows in cellpadss]) def hex_rgb(colour): ## convert [#]RGB to #RRGGBB and [#]RRGGBB to #RRGGBB  return '#%s' % (colour if len(colour) > 4 else ''.join([c * 2 for c in colour])).lstrip('#') def viscam_colour(colour):  colour_hex      = hex_rgb(colour)  colour_top5bits = [int(colour_hex[i:i+2], 16) >> 3 for i in range(1,7,2)]  return (1 << 15) + (colour_top5bits[0] << 10) + (colour_top5bits[1] << 5) + colour_top5bits[2] def roundm(x, multiple=1):  if   (isinstance(x, tuple)): return tuple(roundm(list(x), multiple))  elif (isinstance(x, list )): return [roundm(x_i, multiple) for x_i in x]  else: return int(math.floor(float(x) / multiple + 0.5)) * multiple def average(xs): return None if (len(xs) == 0) else float(sum(xs)) / len(xs) def flatten(lss): return [l for ls in lss for l in ls] def rotate(facetss, degs): ## around x then y then z axes  (deg_x,deg_y,deg_z) = degs  (sin_x,cos_x) = (math.sin(math.radians(deg_x)), math.cos(math.radians(deg_x)))  (sin_y,cos_y) = (math.sin(math.radians(deg_y)), math.cos(math.radians(deg_y)))  (sin_z,cos_z) = (math.sin(math.radians(deg_z)), math.cos(math.radians(deg_z)))  facet_rotatess = []  for facets in facetss:   facet_rotates = []   for i_point in range(4):    (x,y,z) = [facets[3 * i_point + i_xyz] for i_xyz in range(3)]    if (x is None or y is None or z is None): facet_rotates += [x,y,z]     else:     (y,z) = (y * cos_x - z * sin_x, y * sin_x + z * cos_x) ## rotate about x     (x,z) = (x * cos_y + z * sin_y,-x * sin_y + z * cos_y) ## rotate about y     (x,y) = (x * cos_z - y * sin_z, x * sin_z + y * cos_z) ## rotate about z     facet_rotates += [round(value, 9) for value in [x,y,z]]   facet_rotatess.append(facet_rotates)  return facet_rotatess def translate(facetss, ds): ## ds = (dx,dy,dz)  return [facets[:3] + [facets[3 * i_point + i_xyz] + ds[i_xyz]                        for i_point in range(1,4) for i_xyz in range(3)]  for facets in facetss] def flip(facetss): return [facets[:3]+facets[6:9]+facets[3:6]+facets[9:] for facets in facetss]  def cube_xyz_to_sphere_xyz(cube_xyzs):  (x,y,z)                         = [float(xyz) for xyz in cube_xyzs]  (x_squared,y_squared,z_squared) = (x * x,y * y,z * z)  return (x * (1 - (y_squared + z_squared) / 2 + y_squared * z_squared / 3) ** 0.5,          y * (1 - (x_squared + z_squared) / 2 + x_squared * z_squared / 3) ** 0.5,          z * (1 - (y_squared + x_squared) / 2 + y_squared * x_squared / 3) ** 0.5) def xyz_to_lla(xyzs):  (x,y,z) = xyzs  alt     = (x * x + y * y + z * z) ** 0.5  lon     = math.atan2(y, x)  lat     = math.asin(z / alt)  return (lat,lon,alt) deg_90 = math.pi / 2 def find_alt(lat_lons, altss):   (lat,lon) = lat_lons   if   (lat ==  deg_90): alt = average(altss[ 0])   elif (lat == -deg_90): alt = average(altss[-1])   else:    (width,height) = (len(altss[0]),len(altss))    x              = (0.5 + lon / (deg_90 * 4) + lat_offset) * width    y              = (0.5 - lat / (deg_90 * 2)             ) * height    (x_int,y_int)  = (int(x)   , int(y)   )    (x_dec,y_dec)  = (x - x_int, y - y_int)    (x0,x1)        = (x_int % width , (x_int + 1) % width )    (y0,y1)        = (y_int % height, (y_int + 1) % height)    alt            = ((altss[y0][x0] * (1 - x_dec) + altss[y1][x0] * x_dec) * (1 - y_dec) +                      (altss[y0][x1] * (1 - x_dec) + altss[y1][x1] * x_dec) *      y_dec)   # print(map(math.degrees, lat_lons), y,x, alt)   return alt def radius_wgs84(lat):  if (lat in radius_wgs84.cachess): return radius_wgs84.cachess[lat]  (sin_lat, cos_lat)        = (math.sin(lat), math.cos(lat))  ff                        = (1 - f_wgs84) ** 2  c                         = 1 / (cos_lat ** 2 + ff * sin_lat ** 2) ** 0.5  s                         = c * ff  radius_c_s_s              = (radius_datum * c, radius_datum * s)  radius_wgs84.cachess[lat] = radius_c_s_s  return radius_c_s_s radius_wgs84.cachess = {} def lla_to_sphere_xyz(llas):  (lat,lon,alt)        = llas  (sin_lat,sin_lon)    = (math.sin(lat),math.sin(lon))  (cos_lat,cos_lon)    = (math.cos(lat),math.cos(lon))  (radius_c, radius_s) = [(c_s_radius + alt * km_per_luma) * scale                          for c_s_radius in radius_wgs84(lat)]  return (radius_c * cos_lat * cos_lon,radius_c * cos_lat * sin_lon,radius_s * sin_lat) def xyz_alt_to_xyza(xyzs, altss):  (lat,lon,alt) = xyz_to_lla(xyzs)  alt           = find_alt((lat,lon), altss)  lla_alts      = [list(lla_to_sphere_xyz((lat,lon,alt))), alt]  return lla_alts  log("Read elevation data") png_alt = Png(path_png_alt) if (png_alt.metadatas['planes'] != 1): print("%s not 1-channel PNG" % (path_png_alt)); sys.exit(1) log(png_alt) altss = [[png_alt.pixels[png_alt.width * y + x] - luma_datum           for x in range(png_alt.width)] for y in range(png_alt.height)] ## altss[y][x]  log("Find vertices") k       = 2.0 / n_division range_k = range(n_division + 1) face_vertex_llassss = [ ## [0=top][i_y][i_x][xyz,alt]  [[xyz_alt_to_xyza((x*k-1,y*k-1,    1), altss) for y in range_k] for x in range_k],  [[xyz_alt_to_xyza((x*k-1,   -1,y*k-1), altss) for y in range_k] for x in range_k],  [[xyz_alt_to_xyza((    1,x*k-1,y*k-1), altss) for y in range_k] for x in range_k],  [[xyz_alt_to_xyza((y*k-1,x*k-1,   -1), altss) for y in range_k] for x in range_k],  [[xyz_alt_to_xyza((y*k-1,    1,x*k-1), altss) for y in range_k] for x in range_k],  [[xyz_alt_to_xyza((   -1,y*k-1,x*k-1), altss) for y in range_k] for x in range_k], ]  log("Add facets") ## cube xyz -> ll(a) -> image xy -> a -> sphere xyz facetss = [] for (i_face,face_vertex_llasss) in enumerate(face_vertex_llassss):  for  v in range(n_division):   for u in range(n_division):    (xyz00, alt00) = face_vertex_llasss[v    ][u    ]    (xyz01, alt01) = face_vertex_llasss[v    ][u + 1]    (xyz10, alt10) = face_vertex_llasss[v + 1][u    ]    (xyz11, alt11) = face_vertex_llasss[v + 1][u + 1]    (xyz_m, alt_m) = xyz_alt_to_xyza([average(xyzs) for xyzs in zip(*(xyz00,xyz01,xyz10,xyz11))],                                     altss)    if (alt_m > max(alt00,alt01,alt10,alt11) or alt_m < min(alt00,alt01,alt10,alt11)):     facetss.append([None,0,0] + xyz_m + xyz00 + xyz10)     facetss.append([None,0,0] + xyz_m + xyz10 + xyz11)     facetss.append([None,0,0] + xyz_m + xyz11 + xyz01)     facetss.append([None,0,0] + xyz_m + xyz01 + xyz00)    else:     if (abs(alt00 - alt11) < abs(alt01 - alt10)):      facetss.append([None,0,0] + xyz00 + xyz10 + xyz11)      facetss.append([None,0,0] + xyz11 + xyz01 + xyz00)     else:      facetss.append([None,0,0] + xyz10 + xyz11 + xyz01)      facetss.append([None,0,0] + xyz01 + xyz00 + xyz10)  log("Calculate normals") for facets in facetss:  if (facets[0] is None or facets[1] is None or facets[2] is None):   us      = [facets[i_xyz + 9] - facets[i_xyz + 6] for i_xyz in range(3)]   vs      = [facets[i_xyz + 6] - facets[i_xyz + 3] for i_xyz in range(3)]   normals = [us[1]*vs[2] - us[2]*vs[1], us[2]*vs[0] - us[0]*vs[2], us[0]*vs[1] - us[1]*vs[0]]   normal_length = sum([component * component for component in normals]) ** 0.5   facets[:3] = [-round(component / normal_length, 10) for component in normals]  # log(tabbify([['N%s'  % (xyz   )                   for xyz in list('xyz')] + #              ['%s%d' % (xyz, n) for n in range(3) for xyz in list('XYZ')] + ['RGB']] + facetss))  log("Compile STL") outss = ([[('STL\n\n%-73s\n\n' % (header[:73])).encode('utf-8'), struct.pack('<L',len(facetss))]] +          [[struct.pack('<f',float(value)) for value in facets[:12]] +           [struct.pack('<H',0 if (len(facets) <= 12) else                             viscam_colour(facets[12]))] for facets in facetss]) out   = b''.join([bytes(out) for outs in outss for out in outs]) # out += ('\n\n## Python script to generate STL\n\n%s\n' % (open(__file__).read())).encode('utf-8') log("Write STL") with open(__file__[:__file__.rfind('.')] + '.stl', 'wb') as f_out: f_out.write(out) log("#bytes:%d\t#facets:%d\ttitle:\"%-73s\"" % (len(out), len(facetss), header[:73]))