#! /usr/bin/gawk -f
# Last edited on 1999-02-13 21:03:44 by stolfi

BEGIN {
  abort = -1;
  usage = ( \
    "pebbles-make.awk \\\n" \
    "  > pebbles.incx" \
  );
  
  # Generates a POVRay "#include" file that defines the pebbles
  # expected by ring.incx, namely pebble_K_NN where
  # K is a color gun index (0..2) and NN an age index (00..15).
  
  nAges = 16;
  core_y_fin = 0.50
  core_y_mid = (2-core_y_fin)+2*sqrt(1-core_y_fin);
  
  make_pebbles();
}

function make_pebbles(  gun,age)
{
  # Writes a POV include file to standard output.

  write_pov_header();
  for (gun=0; gun<3; gun++)
    { for (age=0; age<nAges; age++)
        { 
          write_pov_item(gun, age);
        }
    }
  
  write_pov_tailer();
}

function write_pov_header()
{
  printf "//  Pebbles\n";
  printf "//  Created by pebbles-make.awk - DO NOT EDIT\n";
  printf "\n";
  printf "//  Requires\n";
  printf "//  Defines\n";
  printf "//    pebble_K_NN\n";
  printf "//      where K={0,1,2} NN={00..%02d}\n", nAges-1;
  printf "\n";
}

function write_pov_item(gun,age,  r,g,b, sy,sr,sg,sb, hy,hr,hg,hb, amb,dif,spc, sz,hrad)
{
  # Writes a pebble declaration for the given "gun" (0,1,2)
  # and the given pebble "age"

  # basic hue "r,g,b":
  if (gun == 0)
    { r=1; g=0; b=0; }
  else if (gun == 1)
    { r=0; g=1; b=0; }
  else
    { r=0; g=0; b=1; }
  
  # evolution parameter "t" in [0_1]
  if (age == 0) 
    { t = 0; hrad = 0; }
  else
    { t = age/(nAges-1); t = t*t;
      t = core_y_fin*t + core_y_mid*t*(1 - t);
    }

  # nominal pebble luminosity "y"
  sy = 1.1 * t;
  if (sy > 1) { sy = 1; }
  if (sy < 0) { sy = 0; }

  # pebble color "sr,sg,sb":
  sr = (1-sy)*0.15 + sy*r;
  sg = (1-sy)*0.15 + sy*g;
  sb = (1-sy)*0.15 + sy*b;
  
  # pebble finish "amb,dif,spc":
  amb = sy;
  dif = 0.90*(1 - amb);
  spc = 0.50*(1 - amb);

  # pebble thickness "sz"
  # sz = 0.33333 + 0.33333*t;
  sz = 0.33333;
  
  # halo radius "hrad"
  # hrad = 2.5*t;
  hrad = 0;

  # extra halo luminosity "hy"
  hy = 0.5*t;

  # halo color "hr,hg,hb":
  hr = (1-hy)*r + hy;
  hg = (1-hy)*g + hy;
  hb = (1-hy)*b + hy;
  
  printf "#declare pebble_%d_%02d = %s\n", gun, age, (hrad > sz ? "union{" : "");
  printf "  sphere{ <0,0,0>, 1\n";
  printf "    texture{\n";
  printf "      pigment { color rgb < %5.3f, %5.3f, %5.3f > }\n", sr, sg, sb;
  printf "      finish { ambient %5.3f diffuse %5.3f specular %5.3f roughness 0.01 }\n", \
                 amb, dif, spc;
  printf "    }\n";
  printf "    scale <1.00,1.00,%.2f>\n", sz;
  printf "  }\n";

  if (hrad > sz)
    { printf "  sphere{ <0,0,0>, 1 hollow\n";
      printf "    pigment { color rgbt <1,1,1,1> }\n";
      printf "    interior{ \n";
      printf "      media{ \n";
      printf "        emission rgb <%5.3f, %5.3f, %5.3f>\n", hr, hg, hb;
      printf "        density{ spherical scallop_wave }\n";
      printf "      }\n";
      printf "    }\n";
      printf "    scale %5.3f\n", hrad;
      printf "  }\n";
    }
  if (hrad > sz) { printf "}\n"; }
  printf "\n";
}

function write_pov_tailer()
{
  printf "//  Done.\n";
}

function arg_error(msg)
{
  printf "*** %s\n", msg > "/dev/stderr";
  abort = 1; exit abort;
}