hexagon-pavilion.arch

# A hexagonal garden pavilion: six trapezoidal galleries ringing a circular rotunda.
#
# Every other example in examples/ is built from rectangles, because that is what a
# floor plan usually is. This one is not rectangular ANYWHERE, and it exists to show
# that the two non-rectilinear room forms compose with a curved wall:
#
#   room … polygon (x,y) …            an explicit ring — exact shoelace area, label at
#                                     the centroid, no bounding box anywhere in the answer
#   room … circle at (cx,cy) radius   a round floor, area measured as exactly piR^2
#   arc (x,y) radius R                a curved WALL EDGE, drawn as a true SVG/DXF arc
#
# THE HEXAGON IS NOT REGULAR, AND THAT IS THE POINT. A regular hexagon of circumradius R
# carries four of its vertices at y = +/- R*sqrt(3)/2 — an irrational number no grid can
# express — so its sloped facades never measure a round anything: set one out at R = 7500
# on a 50 mm grid and each nominal 7500 edge comes back 7504. A drawing that calls that
# 7500 is lying, and one that calls it 7504 looks like a mistake. So this shell is built
# on a 3-4-5 triangle instead. Every sloped facade steps 4500 across and 6000 down, which
# is exactly 7500, and every vertex lands on the grid:
#
#     (16000,7000) (11500,1000) (5500,1000) (1000,7000) (5500,13000) (11500,13000)
#
# Four facades of 7500, two of 6000, 15000 x 12000 overall — and every number on the sheet
# is a whole millimetre a builder can set out with a tape.
#
# A second hexagon at exactly half scale sits inside it. The six galleries are the
# trapezoids BETWEEN the two: four points each, two outer vertices and the two inner ones
# behind them — 7500 or 6000 on the facade, half that on the inside, 3000 deep. Six radial
# spokes run along the joins, and a masonry drum fills the middle.
#
# The drum is the part worth reading twice. It is written as ONE wall of two semicircular
# `arc` edges (there is no close-an-arc form: a closed curve is the two halves it is), on
# a centreline of radius 3000 and 1200 thick. 3000 is not a free choice: it is the inner
# hexagon's INRADIUS, so the drum's centreline is the circle inscribed in that hexagon,
# touching all six of the galleries' inner edges. That is what lets the rotunda be
# `room circle … radius 3000` — the same centreline, which is the ordinary ArchLang
# convention that a room's boundary is its wall's centreline, and the reason each gallery
# counts as ADJACENT to the rotunda rather than 300 mm short of it. The outer face lands
# at 3600, past the inner hexagon's corners at 3354, so the drum swallows the galleries'
# inner edge instead of leaving a crescent of unwalled floor behind it, and
# `dim diameter rotunda` calls out a round phi 6000. The six cased openings are positioned
# `on drum at <pct>`, which walks the wall by ARC LENGTH — so 8.333% is 30 degrees, square
# onto the middle of a gallery.
#
# Three things a hexagon teaches about ANNOTATION.
#
#   1. `dims auto overall` is the only auto mode worth having here: it gives the building
#      one bounding chain, one R leader per distinct arc and one phi per circular room.
#      The room and wall chains have no axis to lie along on a 53-degree facade, so the
#      two north facades are dimensioned BY HAND. Endpoint ORDER is what puts each line
#      outside, because the offset runs along the LEFT normal of from->to — write either
#      pair backwards and the line is drawn through the building (`W_DIM_INSIDE`, with a
#      machine-applicable swap). And the OFFSET has to be bigger than it looks: the rule
#      measures the drawn line's midpoint against the building's room-extents BOX, so on
#      a splayed facade clearing the wall is not enough — 1800 is still inside the
#      rectangle, 3000 is out in the margin where a dimension belongs.
#   2. Neither hand dim carries a `text` override, and neither needs one: the facade
#      really is 7500, so that is what the drawing says.
#   3. A polygon room labels itself at its CENTROID, and here the centroid is the worst
#      place available — a 3000-deep trapezoid whose middle is where the drum bulges past
#      it — while the phi call-out is drawn ON the diameter, exactly where the rotunda's
#      own name would go. So every room pins its name by hand with `label "…" at (x,y)`,
#      out on the radius that bisects its own wedge, midway between the drum face and the
#      facade. That is the one place in this file where the author knows something the
#      centroid does not.
#
# The palette is derived from a single colour with `theme from "#2f6f4e"` — one hex value
# becomes the whole set of wall, poche, floor and annotation inks.
plan "Hexagon Pavilion" {
  units mm
  grid 50
  scale 1:50
  north up
  dims auto overall

  theme from "#2f6f4e"

  # ---- shell: the outer hexagon ---------------------------------------------
  # Walked from the east vertex clockwise on the page, so the six facades run
  # 0-7500 north-east, 7500-13500 north, 13500-21000 north-west, 21000-28500 south-west,
  # 28500-34500 south, 34500-42000 south-east. The openings below are positioned in those
  # millimetres rather than percentages, because a hexagon of two edge lengths has no
  # single percentage that means "the middle of a facade".
  wall id=shell exterior thickness 300 {
    (16000,7000)
    (11500,1000)
    (5500,1000)
    (1000,7000)
    (5500,13000)
    (11500,13000)
    close
  }

  # ---- the drum: one full circle, written as its two halves -----------------
  wall id=drum partition thickness 1200 {
    (11500,7000)
    arc (5500,7000) radius 3000
    arc (11500,7000) radius 3000
  }

  # ---- the six spokes -------------------------------------------------------
  # Each runs from an inner hexagon vertex out to the outer vertex beyond it, so the
  # galleries' side edges and these walls are the same six lines.
  wall id=spoke_e  partition thickness 200 { (12250,7000) (16000,7000) }
  wall id=spoke_ne partition thickness 200 { (10000,4000) (11500,1000) }
  wall id=spoke_nw partition thickness 200 { (7000,4000)  (5500,1000) }
  wall id=spoke_w  partition thickness 200 { (4750,7000)  (1000,7000) }
  wall id=spoke_sw partition thickness 200 { (7000,10000) (5500,13000) }
  wall id=spoke_se partition thickness 200 { (10000,10000) (11500,13000) }

  # ---- rooms ----------------------------------------------------------------
  room id=rotunda circle at (8500,7000) radius 3000 label "Rotunda" at (8500,8300) uses hall

  room id=g_ne polygon (16000,7000) (11500,1000) (10000,4000) (12250,7000)
    label "Reading" at (12250,4200) uses living
  room id=g_n  polygon (11500,1000) (5500,1000) (7000,4000) (10000,4000)
    label "Studio" at (8500,2300) uses office
  room id=g_nw polygon (5500,1000) (1000,7000) (4750,7000) (7000,4000)
    label "Tea Room" at (4750,4200) uses dining
  room id=g_sw polygon (1000,7000) (5500,13000) (7000,10000) (4750,7000)
    label "Store" at (4750,9800) uses storage
  room id=g_s  polygon (5500,13000) (11500,13000) (10000,10000) (7000,10000)
    label "Entrance" at (7600,11700) uses entry
  room id=g_se polygon (11500,13000) (16000,7000) (12250,7000) (10000,10000)
    label "Gallery" at (12250,9800) uses living

  # ---- portals: six cased openings on the curve -----------------------------
  opening id=p_ne on drum at 8.333%  width 1400
  opening id=p_n  on drum at 25%     width 1400
  opening id=p_nw on drum at 41.667% width 1400
  opening id=p_sw on drum at 58.333% width 1400
  opening id=p_s  on drum at 75%     width 1400
  opening id=p_se on drum at 91.667% width 1400

  # ---- entrance and glazing -------------------------------------------------
  # The entrance slides. A leaf on hinges would sweep a 1.4 m quarter-disc across the
  # middle of the one room that has to stay clear; a `sliding` leaf sweeps nothing at all,
  # so no swing rule applies to it and the entrance keeps its own floor.
  door id=d_main sliding on shell at 31500 width 1400 slide left

  window id=win_ne on shell at 3750  width 2400
  window id=win_n  on shell at 10500 width 2400
  window id=win_nw on shell at 17250 width 2400
  window id=win_sw on shell at 24750 width 2400
  window id=win_se on shell at 38250 width 2400

  # ---- dimensions -----------------------------------------------------------
  dim diameter rotunda
  dim (16000,7000)->(11500,1000) offset 3000
  dim (5500,1000)->(1000,7000)   offset 3000

  # ---- loose furniture ------------------------------------------------------
  # Polygon rooms refuse the anchor forms (E_PLACE_POLY — a nine-point anchor needs a
  # rectangle), so every free-standing piece here is an absolute `at`. The two that back
  # onto something use `against wall`, which stays legal on a polygon room because it
  # measures from the WALL and not from the room.
  #
  # An axis-aligned piece in a wedge gallery has to be set out against a SLOPED wall, and
  # its far corner is what reaches that wall first — not its edge. Both benches below sat
  # 100-130 mm inside a wall solid until `W_FURNITURE_WALL_COLLISION` learned to measure a
  # wall that is not axis-aligned; nothing had ever checked. Keep them west of where they
  # were: f_bench clears the sloped south-east facade, f_seat clears spoke_se.
  furniture id=f_desk  counter against wall shell segment 1 offset 3000 size 3000x500 label "Work bench" in g_n
  furniture id=f_shelf counter against wall spoke_w offset 1400 size 1200x600 label "Shelves" in g_sw
  furniture id=f_read  table at (13150,5550)  size 900x900  label "Table" in g_ne
  furniture id=f_tea   table at (3850,5550)   size 900x900  label "Tea"   in g_nw
  furniture id=f_bench bench at (12950,8450)  size 1400x450 label "Bench" in g_se
  furniture id=f_seat  bench at (9450,12000)  size 1400x450 label "Bench" in g_s

  title {
    project "Hexagon Pavilion"
    drawn_by "ArchLang"
    date "2026-08-16"
  }
}