tweaks

README.md

@@ -1,6 +1,6 @@
 # MoonModel
 
-MoonModel creates hollow, terrain-accurate lunar globes as generic, material-aware 3MF files. It supports a one-piece display Moon, an eight-section large Moon, arbitrary named filament colors, nozzle-aware tonal dithering, optional coordinate lines, magnetic-box configuration, and a separate orbital-triskelion stand.
+MoonModel creates terrain-accurate lunar globes as generic, material-aware 3MF files. It supports a solid one-piece display Moon intended for slicer-controlled sparse infill, an optional hollow one-piece Moon, a hollow eight-section large Moon, arbitrary named filament colors, nozzle-aware tonal dithering, optional coordinate lines, magnetic-box configuration, and a separate orbital-triskelion stand.
 
 ## Setup and use
 
@@ -15,13 +15,13 @@ The executable begins with `require "bundler/setup"`, so all application imports
 bundle exec ruby bin/moon_model --config config/example.yml --output build/example
 ```
 
-The wizard first asks for a model name, then asks about the printer/tooling envelope, intended use, palette, grid, size or scale, vertical exaggeration, and assembly hardware. Named models are written to `build/<name>/`. Selecting an existing generated name offers to revise it, using its saved configuration as the defaults for a fresh wizard run. It displays maximum one-piece/eight-section sizes in millimeters and inches and a terrain-relief cheat sheet before generation.
+The wizard first asks for a model name, then asks about the printer/tooling envelope, intended use, palette, grid, size or scale, one-piece interior, vertical exaggeration, and assembly hardware. Named models are written to `build/<name>/`. Selecting an existing generated name offers to revise it, using its saved configuration as the defaults for a fresh wizard run. It displays maximum one-piece/eight-section sizes in millimeters and inches and a terrain-relief cheat sheet before generation.
 
 ## Output
 
-One-piece runs create `moon.3mf`. Segmented runs create eight print files, an assembled preview, and an assembly-key file. The optional one-piece, support-free orbital stand is emitted as `orbital_triskelion_stand.3mf` without a material assignment; its footprint scales with the Moon and is capped to the usable printer bed. Its saddles use conservative terrain-radius bounds so the Moon can be rotated freely while retaining a configurable 10 mm default clearance above the central hub. Every run includes its reusable YAML configuration, a slicer/spool manifest, and assembly instructions. Revisions are generated in a temporary directory and atomically replace the prior generated directory only after successful validation; unrelated directories are never overwritten. `--output DIR` continues to override the named default location.
+One-piece runs create `moon.3mf`. Their interior defaults to a watertight solid volume so the slicer can apply balanced sparse infill without generating inaccessible cavity supports; `shell.interior: hollow` retains the thin-wall alternative. Segmented runs remain hollow and create eight print files, an assembled preview, and an assembly-key file. The optional one-piece, support-free orbital stand is emitted as `orbital_triskelion_stand.3mf` without a material assignment; its footprint scales with the Moon and is capped to the usable printer bed. Its saddles use conservative terrain-radius bounds so the Moon can be rotated freely while retaining a configurable 10 mm default clearance above the central hub. Every run includes its reusable YAML configuration, a slicer/spool manifest, and assembly instructions. Revisions are generated in a temporary directory and atomically replace the prior generated directory only after successful validation; unrelated directories are never overwritten. `--output DIR` continues to override the named default location.
 
-Colors are closed surface inlay volumes over a continuous structural shell. Palette entry order defines filament slots 1 through N. The 3MF records portable material names/display colors and Bambu Studio part names/slot assignments; confirm the numbered slots against physical AMS or external-spool filaments. The structural shell and first-color surface remain separate bodies assigned to the same filament 1, so an N-color Moon may show N+1 bodies. The file has no fixed palette limit, though the printer and filament system will impose practical limits.
+Colors are closed surface inlay volumes over a continuous structural body. Palette entry order defines filament slots 1 through N. The 3MF records portable material names/display colors and Bambu Studio part names/slot assignments; confirm the numbered slots against physical AMS or external-spool filaments. The structural body and first-color surface remain separate bodies assigned to the same filament 1, so an N-color Moon may show N+1 bodies. The file has no fixed palette limit, though the printer and filament system will impose practical limits.
 
 ## Modeling notes
 

config/example.yml

@@ -19,6 +19,8 @@ palette:
 grid:
   enabled: false
   interval_degrees: 30
+shell:
+  interior: solid
 stand:
   enabled: true
   style: orbital_triskelion

config/example_box.yml

@@ -16,6 +16,7 @@ grid:
   interval_degrees: 30
   line_width_mm: 1.2
   color_name: Highland silver
+shell: {interior: hollow}
 magnets: {diameter_mm: 6, thickness_mm: 3, count: 8}
 stand: {enabled: true, style: orbital_triskelion, base_clearance_mm: 10.0, material: null}
 resolution: {longitude_segments: 360}

lib/moon_model/config.rb

@@ -70,6 +70,7 @@ module MoonModel
     def derive!
       nozzle = Float(data["nozzle_mm"])
       shell = data["shell"]
+      shell["interior"] ||= "solid"
       shell["wall_mm"] ||= 4.0 * nozzle
       shell["inlay_depth_mm"] ||= 2.0 * nozzle
       shell["minimum_feature_mm"] ||= 2.0 * nozzle
@@ -84,6 +85,7 @@ module MoonModel
       raise ArgumentError, "build volume requires three positive dimensions" unless build_volume.length == 3 && build_volume.all?(&:positive?)
       raise ArgumentError, "purpose must be display or box" unless %w[display box].include?(self["purpose"])
       raise ArgumentError, "assembly must be auto, one_piece, or eight_piece" unless %w[auto one_piece eight_piece].include?(self["assembly"])
+      raise ArgumentError, "shell interior must be solid or hollow" unless %w[solid hollow].include?(self["shell"]["interior"])
       raise ArgumentError, "unsupported stand style" unless self["stand"]["style"] == "orbital_triskelion"
       raise ArgumentError, "stand base clearance must be nonnegative" if Float(self["stand"]["base_clearance_mm"]).negative?
       raise ArgumentError, "palette must contain at least one color" if self["palette"].empty?

lib/moon_model/generator.rb

@@ -166,6 +166,7 @@ module MoonModel
 
         - Mode: #{result.segmented? ? "eight section" : "one piece"} (#{result.mode_source})
         - Purpose: #{config["purpose"]}
+        - Interior: #{result.statistics["interior"] == "solid" ? "solid slicer volume (use configured infill)" : "hollow shell"}
         - Datum diameter: #{format("%.2f", result.statistics["diameter_mm"])} mm (#{format("%.3f", result.statistics["diameter_mm"] / 25.4)} in)
         - Final terrain envelope: #{format("%.2f", result.statistics["final_envelope_mm"])} mm (#{format("%.3f", result.statistics["final_envelope_mm"] / 25.4)} in)
         - Vertical exaggeration: #{config["vertical_exaggeration"]}×
@@ -186,7 +187,7 @@ module MoonModel
         |---|---|---:|
         #{bodies}
 
-        The structural shell remains separate from the colored surface. Both the structure and the first-color surface use filament 1, so an N-color Moon can contain N+1 bodies. The 3MF contains standard material names/colors plus Bambu Studio part names and slot assignments; confirm physical AMS or external-spool mappings in the slicer. The stand intentionally has no material assignment.
+        The structural volume remains separate from the colored surface. Both the structure and the first-color surface use filament 1, so an N-color Moon can contain N+1 bodies. The 3MF contains standard material names/colors plus Bambu Studio part names and slot assignments; confirm physical AMS or external-spool mappings in the slicer. The stand intentionally has no material assignment.
 
         ## Files
 
@@ -241,7 +242,15 @@ module MoonModel
           4. Apply adhesive to the recessed equatorial land, align longitude seams, and close the second hemisphere from the outside.
         MD
       else
-        "# Printing\n\nThe one-piece hollow Moon requires slicer-generated build-plate adhesion and support appropriate to the selected material.\n"
+        if result.statistics["interior"] == "solid"
+          <<~MD
+            # Printing
+
+            The one-piece Moon is a watertight solid slicer volume. Select the desired sparse infill pattern and percentage in the slicer; no internal cavity supports are required. Configure build-plate adhesion and external support for the lower surface as appropriate to the selected material and printer.
+          MD
+        else
+          "# Printing\n\nThe one-piece hollow Moon requires slicer-generated build-plate adhesion and support appropriate to the selected material. Internal supports may be difficult to remove and can break loose inside the finished Moon.\n"
+        end
       end
       path = File.join(write_dir, "ASSEMBLY.md")
       File.write(path, text)

lib/moon_model/geometry.rb

@@ -9,12 +9,13 @@ module MoonModel
 
     def build(config, data_set)
       sizing = Sizing.calculate(config, data_set)
+      interior = sizing.segmented? ? "hollow" : config["shell"]["interior"]
       diameter = sizing.datum_diameter_mm
       lon_segments = sizing.longitude_segments
       lat_segments = sizing.latitude_segments
       palette = Color.ordered_palette(config["palette"])
       ranges = sizing.segmented? ? section_ranges : [[-90.0, 90.0, 0.0, 360.0, "moon"]]
-      parts = build_parts(config, data_set, diameter, ranges, lon_segments, lat_segments, palette)
+      parts = build_parts(config, data_set, diameter, ranges, lon_segments, lat_segments, palette, interior)
       radius = diameter / 2.0
       all_meshes = parts.flat_map { |part| part[:meshes] }
       keys = sizing.segmented? ? build_keys(config, radius) : []
@@ -36,6 +37,7 @@ module MoonModel
                       "safe_exaggeration" => sizing.safe_exaggeration, "mode" => sizing.mode, "mode_source" => sizing.mode_source,
                       "longitude_segments" => lon_segments,
                       "latitude_segments" => lat_segments, "part_count" => parts.length,
+                      "interior" => interior,
                       "minimum_radius_mm" => sizing.minimum_radius_mm,
                       "maximum_radius_mm" => sizing.maximum_radius_mm,
                       "relief_range_mm" => relief_range_mm(config, data_set, diameter),
@@ -53,10 +55,10 @@ module MoonModel
       requested
     end
 
-    def build_parts(config, data_set, diameter, ranges, lon_segments, lat_segments, palette)
+    def build_parts(config, data_set, diameter, ranges, lon_segments, lat_segments, palette, interior)
       radius = diameter / 2.0
       ranges.map do |lat0, lat1, lon0, lon1, name|
-        build_patch(config, data_set, radius, lat0, lat1, lon0, lon1, name, lon_segments, lat_segments, palette)
+        build_patch(config, data_set, radius, lat0, lat1, lon0, lon1, name, lon_segments, lat_segments, palette, interior)
       end
     end
 
@@ -67,13 +69,14 @@ module MoonModel
       end
     end
 
-    def build_patch(config, data_set, radius, lat0, lat1, lon0, lon1, name, global_lon_segments, global_lat_segments, palette)
+    def build_patch(config, data_set, radius, lat0, lat1, lon0, lon1, name, global_lon_segments, global_lat_segments, palette, interior)
       nlon = [(global_lon_segments * (lon1 - lon0) / 360.0).round, 2].max
       nlat = [(global_lat_segments * (lat1 - lat0) / 180.0).round, 2].max
       base = Mesh.new(name: "#{name}_structure", material: config["palette"].first)
       color_meshes = palette.to_h { |color| [color["name"], Mesh.new(name: "#{name}_#{slug(color["name"])}", material: color)] }
       multicolor = palette.length > 1
-      unified_base = multicolor || !config["grid"]["enabled"]
+      solid = interior == "solid"
+      unified_base = solid || multicolor || !config["grid"]["enabled"]
       substrate_vertices = {}
       inner_vertices = {}
       boundary_edges = {}
@@ -99,26 +102,35 @@ module MoonModel
             else
               0.0
             end
-            substrate = coords.map { |lat, lon| point(config, data_set, radius, lat, lon, surface_offset) }
+            substrate = if solid && !multicolor && config["grid"]["enabled"]
-            inner = coords.map { |lat, lon| point(config, data_set, radius, lat, lon, -config["shell"]["wall_mm"]) }
+              coords.map do |lat, lon|
+                vertex_is_grid = on_grid?(config, lat, lon, radius, (a1 - a0).abs / 2.0, (o1 - o0).abs / 2.0)
+                point(config, data_set, radius, lat, lon, vertex_is_grid ? -config["grid"]["depth_mm"] : 0.0)
+              end
+            else
+              coords.map { |lat, lon| point(config, data_set, radius, lat, lon, surface_offset) }
+            end
+            inner = solid ? nil : coords.map { |lat, lon| point(config, data_set, radius, lat, lon, -config["shell"]["wall_mm"]) }
             if unified_base
               outer_ids = coords.each_with_index.map do |coord, index|
                 substrate_vertices[coordinate_key(coord)] ||= base.vertex(substrate[index])
               end
-              inner_ids = coords.each_with_index.map do |coord, index|
-                inner_vertices[coordinate_key(coord)] ||= base.vertex(inner[index])
-              end
               base.triangle(*outer_ids)
-              base.triangle(inner_ids[0], inner_ids[2], inner_ids[1])
+              unless solid
-              3.times do |edge|
+                inner_ids = coords.each_with_index.map do |coord, index|
-                next_edge = (edge + 1) % 3
+                  inner_vertices[coordinate_key(coord)] ||= base.vertex(inner[index])
-                key = [coordinate_key(coords[edge]), coordinate_key(coords[next_edge])].sort
+                end
-                record = boundary_edges[key]
+                base.triangle(inner_ids[0], inner_ids[2], inner_ids[1])
-                if record
+                3.times do |edge|
-                  record[:count] += 1
+                  next_edge = (edge + 1) % 3
-                else
+                  key = [coordinate_key(coords[edge]), coordinate_key(coords[next_edge])].sort
-                  boundary_edges[key] = { count: 1, outer: [outer_ids[edge], outer_ids[next_edge]],
+                  record = boundary_edges[key]
-                                          inner: [inner_ids[edge], inner_ids[next_edge]] }
+                  if record
+                    record[:count] += 1
+                  else
+                    boundary_edges[key] = { count: 1, outer: [outer_ids[edge], outer_ids[next_edge]],
+                                            inner: [inner_ids[edge], inner_ids[next_edge]] }
+                  end
                 end
               end
             else
@@ -135,6 +147,7 @@ module MoonModel
       if unified_base
         boundary_edges.each_value do |edge|
           next unless edge[:count] == 1
+          next if solid
           base.quad(edge[:outer][0], edge[:outer][1], edge[:inner][1], edge[:inner][0])
         end
       end

lib/moon_model/sizing.rb

@@ -40,12 +40,13 @@ module MoonModel
       dimensions = unit.map { |min, max| (max - min) * datum }
       minimum_radius, maximum_radius = conservative_radial_bounds(config, data_set, datum, exaggeration,
                                                                    lon_segments, lat_segments)
-      safe = validate_safety ? maximum_safe_exaggeration(config, data_set) : nil
+      interior = prospective_interior(config, data_set, datum, exaggeration, lon_segments, lat_segments)
+      safe = validate_safety ? maximum_safe_exaggeration(config, data_set, interior: interior) : nil
       if safe && exaggeration > safe + 1e-9
         raise ArgumentError, format("vertical exaggeration %.3gx is unsafe; maximum is %.3gx", exaggeration, safe)
       end
-
       mode, source = resolve_mode(config, data_set, datum, exaggeration, lon_segments, lat_segments)
+
       Result.new(
         datum_diameter_mm: datum,
         final_envelope_mm: dimensions.max,
@@ -61,6 +62,14 @@ module MoonModel
       )
     end
 
+    def prospective_interior(config, data_set, datum, exaggeration, lon_segments, lat_segments)
+      return "hollow" if config["purpose"] == "box" || config["assembly"] == "eight_piece"
+      return config["shell"]["interior"] if config["assembly"] == "one_piece"
+
+      dimensions = full_dimensions(data_set, datum, exaggeration, lon_segments, lat_segments)
+      fits?(dimensions, config) ? config["shell"]["interior"] : "hollow"
+    end
+
     def conservative_radial_bounds(config, data_set, datum, exaggeration, lon_segments, lat_segments)
       base_radius = datum / 2.0
       radii = (0..lat_segments).flat_map do |iy|
@@ -112,11 +121,13 @@ module MoonModel
       bounds
     end
 
-    def maximum_safe_exaggeration(config, data_set)
+    def maximum_safe_exaggeration(config, data_set, interior: config["shell"]["interior"])
       minimum_offset = data_set.metadata.fetch("elevation_offset_range_m", [-data_set.relief_range_m, 0]).first.to_f
       return Float::INFINITY unless minimum_offset.negative?
 
-      required = config["shell"]["wall_mm"] + config["shell"]["minimum_feature_mm"]
+      solid = interior == "solid"
+      required = config["shell"]["minimum_feature_mm"]
+      required += config["shell"]["wall_mm"] unless solid
       if config["size"]["meaning"] == "datum"
         available = config.diameter_mm / 2.0
         return 0.0 if available <= required
@@ -132,7 +143,8 @@ module MoonModel
         mid = (low + high) / 2.0
         factor = sampled_bounds(data_set, mid, segment_count(config), segment_count(config) / 2).map { |a, b| b - a }.max
         radius = config.diameter_mm / (2.0 * factor)
-        inner = radius * (1.0 + minimum_offset / DataSet::DATUM_RADIUS_M * mid) - config["shell"]["wall_mm"]
+        inner = radius * (1.0 + minimum_offset / DataSet::DATUM_RADIUS_M * mid)
+        inner -= config["shell"]["wall_mm"] unless solid
         inner >= config["shell"]["minimum_feature_mm"] ? low = mid : high = mid
       end
       low

lib/moon_model/wizard.rb

@@ -152,6 +152,10 @@ module MoonModel
         end
         values["size"] = { "input" => "diameter", "value" => value, "unit" => unit, "meaning" => meaning }
       end
+      shell = values.fetch("shell", {}).dup
+      shell["interior"] = yes_no("For a one-piece Moon, use slicer-controlled infill instead of a hollow cavity?",
+                                  shell.fetch("interior", "solid") == "solid") ? "solid" : "hollow"
+      values["shell"] = shell
       io.say("Terrain sizing at this size:")
       [1, 2, 5, 10].each do |factor|
         trial = Config.new(values.merge("vertical_exaggeration" => factor))
@@ -179,6 +183,10 @@ module MoonModel
       io.say("Datum diameter: #{units(summary.datum_diameter_mm)}")
       io.say("Finished envelope: #{units(summary.final_envelope_mm)}; relief #{format('%.3f', summary.relief_range_mm)} mm")
       io.say("Maximum safe exaggeration: #{format('%.2f', summary.safe_exaggeration)}x; mode: #{summary.mode.tr('_', ' ')} (#{summary.mode_source})")
+      if summary.segmented?
+        values["shell"]["interior"] = "hollow"
+        io.say("Eight-section output uses hollow sections; the solid/infill option applies only to one-piece Moons.")
+      end
     end
 
     def engineering(values)

test/config_test.rb

@@ -9,6 +9,7 @@ class ConfigTest < Minitest::Test
     assert_in_delta 463.0, config.maximum_diameter("eight_piece"), 0.001
     assert_in_delta 1.6, config["shell"]["wall_mm"], 0.001
     assert_in_delta 0.8, config["shell"]["minimum_feature_mm"], 0.001
+    assert_equal "solid", config["shell"]["interior"]
     assert_in_delta 10.0, config["stand"]["base_clearance_mm"], 0.001
   end
 
@@ -32,4 +33,8 @@ class ConfigTest < Minitest::Test
       MoonModel::Config.new("stand" => { "base_clearance_mm" => -0.1 })
     end
   end
+
+  def test_rejects_unknown_interior_mode
+    assert_raises(ArgumentError) { MoonModel::Config.new("shell" => { "interior" => "foam" }) }
+  end
 end

test/generator_test.rb

@@ -21,6 +21,10 @@ class GeneratorTest < Minitest::Test
         assert_includes model, "<components>"
       end
       assert File.file?(File.join(result[:output_dir], "manifest.md"))
+      manifest = File.read(File.join(result[:output_dir], "manifest.md"))
+      assembly = File.read(File.join(result[:output_dir], "ASSEMBLY.md"))
+      assert_includes manifest, "Interior: solid slicer volume"
+      assert_includes assembly, "no internal cavity supports are required"
       assert_in_delta 40.0, result[:statistics]["final_envelope_mm"], 0.01
     end
   end

test/geometry_test.rb

@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class GeometryTest < Minitest::Test
+  def setup
+    @data = MoonModel::DataSet.new
+  end
+
+  def test_solid_one_piece_is_a_closed_outer_volume_without_inner_surface
+    solid = structure("solid")
+    hollow = structure("hollow")
+
+    assert solid.valid?
+    assert_manifold solid
+    assert_equal hollow.triangles.length / 2, solid.triangles.length
+    assert_equal hollow.vertices.length / 2, solid.vertices.length
+  end
+
+  def test_solid_single_color_grid_remains_manifold
+    config = config_for("solid", "grid" => { "enabled" => true, "depth_mm" => 0.4 })
+    mesh = MoonModel::Geometry.build(config, @data).parts.first[:meshes].first
+
+    assert mesh.valid?
+    assert_manifold mesh
+  end
+
+  def test_segmented_output_is_hollow_even_when_solid_is_requested
+    config = config_for("solid", "purpose" => "box", "assembly" => "eight_piece")
+    result = MoonModel::Geometry.build(config, @data)
+
+    assert result.segmented?
+    assert_equal "hollow", result.statistics["interior"]
+  end
+
+  private
+
+  def structure(interior)
+    MoonModel::Geometry.build(config_for(interior), @data).parts.first[:meshes].first
+  end
+
+  def config_for(interior, extra = {})
+    MoonModel::Config.new({
+      "size" => { "value" => 40 },
+      "shell" => { "interior" => interior },
+      "resolution" => { "longitude_segments" => 24 }
+    }.merge(extra))
+  end
+
+  def assert_manifold(mesh)
+    edge_uses = Hash.new(0)
+    mesh.triangles.each do |triangle|
+      triangle.each_index do |index|
+        edge_uses[[triangle[index], triangle[(index + 1) % 3]].sort] += 1
+      end
+    end
+    assert edge_uses.values.all? { |count| count == 2 }, "every edge must belong to exactly two faces"
+  end
+end

test/sizing_test.rb

@@ -11,11 +11,20 @@ class SizingTest < Minitest::Test
     MoonModel::Config.new(
       "size" => { "input" => "diameter", "value" => 8.0, "unit" => "in", "meaning" => "datum" },
       "vertical_exaggeration" => exaggeration,
-      "assembly" => assembly,
+      "assembly" => assembly, "shell" => { "interior" => "hollow" },
       "resolution" => { "longitude_segments" => 48 }
     )
   end
 
+
+  def test_solid_one_piece_allows_more_relief_before_radial_collapse
+    hollow = datum_config(1, assembly: "one_piece")
+    solid = MoonModel::Config.new(hollow.to_h.merge("shell" => hollow["shell"].merge("interior" => "solid")))
+
+    assert_operator MoonModel::Sizing.maximum_safe_exaggeration(solid, @data), :>,
+                    MoonModel::Sizing.maximum_safe_exaggeration(hollow, @data)
+  end
+
   def test_eight_inch_relief_uses_consistent_units
     one = MoonModel::Sizing.calculate(datum_config(1), @data)
     ten = MoonModel::Sizing.calculate(datum_config(10), @data)

test/wizard_test.rb

@@ -69,6 +69,18 @@ class WizardTest < Minitest::Test
     assert_includes output.string, "waive the recommended terrain safety margin"
   end
 
+  def test_one_piece_interior_choice_can_select_hollow
+    input = StringIO.new("\n\n\n\nn\n\n\n")
+    output = StringIO.new
+    wizard = MoonModel::Wizard.new(io: HighLine.new(input, output), data_set: MoonModel::DataSet.new)
+    values = { "printer" => MoonModel::Config::X2D.dup, "purpose" => "display", "assembly" => "auto" }
+
+    wizard.send(:sizing, values)
+
+    assert_equal "hollow", values.dig("shell", "interior")
+    assert_includes output.string, "use slicer-controlled infill instead of a hollow cavity"
+  end
+
   private
 
   def ask_yes_no(input, default)