Module chain in JSON

gistfile1.json

{
  "modules": [
    { "type": "constant",                "key": "tile_air",                  "value": "1" },
    { "type": "constant",                "key": "tile_dirt",                 "value": "2" },
    { "type": "constant",                "key": "tile_stone",                "value": "3" },
    { "type": "constant",                "key": "tile_copper",               "value": "4" },
    { "type": "constant",                "key": "tile_silver",               "value": "5" },
    { "type": "constant",                "key": "tile_gold",                 "value": "6" },

    { "type": "gradient",                "key": "contour_gradient",          "x0":"0.00", "x1":"0.00", "y0": "0.00", "y1": "1.00" },
    { "type": "fractal",                 "key": "contour_fractal",           "fractal": "fbm", "basis": "gradient", "interpolation": "quintic", "octaves": "3", "frequency": "2.00" },
    { "type": "cache",                   "key": "contour_fractal_cache",     "source": "contour_fractal" },
    { "type": "scale_offset",            "key": "contour_scale",             "source": "contour_fractal_cache", "scale": "0.50", "offset": "0.00" },
    { "type": "scale_domain",            "key": "contour_scale_y",           "source": "contour_scale", "y": "0.00" },
    { "type": "translate_domain",        "key": "contour_perturb",           "source": "contour_gradient", "y": "contour_scale_y" },

    { "type": "scale_offset",            "key": "contour_overhang_scale",    "source": "contour_fractal_cache", "scale": "0.50", "offset": "0.00" },
    { "type": "translate_domain",        "key": "contour_overhang_perturb",  "source": "contour_perturb", "x": "contour_overhang_scale" },

    { "type": "gradient",                "key": "ground_gradient",           "x0":"0.00", "x1":"0.00", "y0": "0.00", "y1": "0.90" },
    { "type": "clamp",                   "key": "ground_gradient_clamp",     "source": "ground_gradient", "low":"0.00", "high": "1.00" },
    { "type": "fractal",                 "key": "ground_fractal",            "fractal": "ridged_multi", "basis": "gradient", "interpolation": "quintic", "octaves": "3", "frequency": "10.00" },

    { "type": "combiner",                "key": "ground_gradient_combiner",  "type": "multiply", 
	  "sources": [
        { "source": "ground_fractal" },
        { "source": "ground_gradient_clamp" }
      ]
    },

    { "type": "select",                  "key": "ground_1",                  "source": "ground_gradient_combiner", "low": "tile_dirt", "high": "tile_stone", "threshold": "0.50" },
    { "type": "select",                  "key": "ground_2",                  "source": "ground_gradient_combiner", "low": "ground_1", "high": "tile_stone", "threshold": "0.80" },
    { "type": "select",                  "key": "ground_select",             "source": "contour_overhang_perturb", "low": "tile_air", "high": "ground_2", "threshold": "0.50" }
  ],
  "source": "ground_select"
}