Each building is a chain of square modules one arm wide, centred on a lattice whose step is half an arm
plus half a footpath. Modules one step apart merge; two steps apart they leave a slot one footpath wide.
Modules of different buildings are never closer than two steps, so every gap is a footpath. Outside corners
are rounded to half the arm width (two make a round end) and inside corners to half the footpath width; the
two radii add up to one step, so the three pieces always fit. The corner pieces can also be a fixed radius
(the same mould on every storey, as large as the top floor allows), hexagonal (ends cut to a point at 60°,
other corners at 45°) or plain square corners. Shapes that would enclose a courtyard, or
have no arm long enough for a stair, are grown again.
Every slab above is the one below inset by the setback, which keeps each corner's centre: convex corners
tighten, concave ones open, and the straight runs keep their length. When the fewest storeys is below the
most, each building's height is drawn at random between the two. Floor areas are measured to the
shopfront glass, 0.8 m behind the slab edge.
Leasable floor is the gross floor less 30 m² a floor in each building for a goods lift and risers, and less
the commercial floor (the retail halls and the industrial floor).
Shopfront tenancies divide the glass frontage into 6 m bays; depth is leasable floor over frontage, so it is
the typical distance from a shopfront to the back of its unit.
Foyers: every building has one on the ground floor, open to the footpath beside the foot of its public stair,
so everyone crossing the building passes through: a coffee counter, tables, and the building's Pipedream hub,
a portal where goods arrive in a grocery tote, carried by robots through pipes laid like any other utility
(Pipedream quotes speeds over 60 mph). The foyer is common space: it comes out of the leasable floor and the
shopfronts.
Loop: each district has a station on open ground near its middle, with a drop-off canopy and an open ramp.
The ramp is 45 m long and eases in at the top and out at the foot. Its walls finish flush with the lawn under
a coping, with a rail where the drop is more than a step. At 5 m down it meets a headwall with two round
tunnel mouths, one for each direction. No footpath crosses a ramp. Twin single-lane tunnels (about 3.7 m
across, 7 m down, below the canals) join the stations of neighbouring districts, in the style of the Boring
Company's Loop. Cars carry a few people at a time, station to station, at an assumed 100 km/h.
Cranes: each district has a gantry crane on one of its canals, half way between two footbridges. Each canal
has one crane at most, and it runs straight for 40 m either side of it. The crane runs on rails 1.2 m in from
both quay edges, so barges pass between its legs. Its girders are 13 m above the towpaths and reach over a
paved yard on each bank. Containers stand in each yard two high, in two rows of four. Every barge on a
crane's canal carries containers. It slows over 30 m and waits 100 s under the crane, going each way. The
crane lifts a container off, sets it down in either yard, and puts another from either yard in its place. It
travels along its rails at 1.4 m/s, moves its trolley at 2.6 m/s and hoists at 1.3 m/s. The barges set off
at times that give each crane one barge at a time.
Industry: the four buildings nearest each crane take industrial trades. These are
freight and storage, fabrication, brewing and distilling, and repair and recycling. Each keeps a ring of
units round its edge: the ground floor's, and the first storey's, 8 m deep behind its glass. Inside that
ring, the floor between the ground and first storeys is left out, so the core of the building is one hall two
storeys high, as long as the building. Columns on a 12 m grid carry the floors above. A passage 12 m wide
leads into the hall from one long straight face, clear of the public stair and the foyer. There the first
terrace is built over, so the face rises two storeys straight from the footpath, with a roller door 6 m wide
and up to 6.5 m tall. On each bank, the building nearest the crane faces it where it can, and paving runs
from that bank's yard to its door. The floor areas, shopfronts and terraces leave out what the halls take. The
trades' other shopfronts are mostly roller doors and profiled cladding. Industrial floor is the ground and first
storeys of each industrial building, less the foyer and the goods lift. The hall and the passage to it are
high bay, two storeys high. The ring of units round them is low bay, one storey high. Industrial floor is not
leasable floor, so it houses no residents. Its units are not counted as shopfront
tenancies.
Retail halls: the middle of a building's lower storeys gets no sun, so it suits a supermarket or another shop
that needs a large floor better than it suits units. In every building with room and no industrial hall, part
of the core behind the same ring of units is one hall two storeys high: a rectangle up to 36 m deep, from the
ring back, as wide as the core allows. It opens off the back of the building's foyer, which becomes its
entrance hall, through a passage under the first storey with a sign over it. Each hall is a supermarket, a hardware store, a furniture showroom or
a market hall. Every hall takes the same share of its own building's floor, the least share that brings the
commercial floor (retail halls and industry) up to the share you set. Halls under 600 m² are left out. The
retail floor is each hall and its entrance. It is not leasable floor, so it houses no residents.
People: residents are the leasable floor divided by the floor each resident takes, a room and a share of
the workshops, shops and studios (80 m² unless you change it). Densities are over the districts' whole land,
rivers, parks and footpaths included, as a city's figure would be.
Terraces are measured inside the parapets, out to the glass of the floor above; roofs inside the roof
parapet. Streets and parks are the site less the ground-floor slabs.
Stairs: risers at most 180 mm, goings 280 mm, 1.25 m wide with a solid cheek wall and a 1.3 m landing.
One flight per storey climbs along the face of the floor it serves, switching back on each terrace, then
the route crosses the roof and comes down the far side the same way. Each building crosses one
arm, near its middle, where both faces run straight for long enough on every storey. When the setback
allows goings of at least 250 mm and the arms leave at least 2 m of roof between the two stairs, the stair
instead runs straight up the face: one flight cut into each storey, footpath to roof, with each terrace
opening off the head of its flight. The setback is capped so the top
floor stays at least 8 m wide.
Ground: lawn everywhere outside the buildings, rolling about a metre either way and levelling out within a
few metres of each building. Districts are hexagons on a honeycomb with a 52 m corridor along every shared
edge; a canal runs down the middle of each (20 m of water between white quay walls, a metre below 5 m
towpaths), meeting the others in a turning basin where three districts meet and running on into the meadow
to a basin where an edge reaches the outside. A lone district gets a canal along its two southern edges.
Barges keep to the right and turn in the basins. Footbridges are level over the water, 3 m above it so a
loaded barge passes under, and ramp down over the towpaths to each bank. With organic outlines, each corner of the honeycomb moves up to a fifth of a side at
random and each side bows and wiggles (fading out at the corners), one curve per side shared by both
districts and their river; modules keep the same distance in from the curve. Inside each hexagon the buildings keep the square module lattice. Footbridges cross each
shared edge from the nearest path point on one side to the nearest on the other.
Footpaths run along the lattice lines that lie in the gaps, a spanning tree with some loops trimmed of dead
ends, and swing sideways as far as the open ground allows. Every stair foot gets a spur.
Sun: solar time, clear sky. The buildings, parapets included, and the ground are drawn into a height map of
0.5 m cells (at most 1,400 across, so coarser for big towns); trees and stairs are left out. From ground points
2 m apart (at most 40,000, spread evenly over big towns) a ray is marched toward the sun, and the point is
in sun if the ray clears every building. Towns more than 7 km across are measured over the middle 7 km.
Daily hours sample every half hour from sunrise to sunset.
Straight walls keep the same footprints and storeys with no setbacks.
Rendering: the sky is sunlight scattered once through 100 km of air (Rayleigh and Mie, with a little more
aerosol than the textbook), with fair-weather cumulus at 1.8 km; the same air reddens the sun as it sets and
hazes the distance. Shade is lit only by an image of that sky. Surfaces (painted render, limestone pavers,
resin-bound gravel, lawn, decking) are painted on the graphics card at start-up and laid on in world space.
Shopfront glass reflects the town round you and shows a room behind each 6 m bay (interior mapping). The
canals mirror the town. Trees are leaf cards on branching limbs, lit through from behind; within 25 m the
lawn grows blades. Ambient occlusion, bloom and a filmic tone curve (AgX) finish the picture, exposed by
metering as a camera would. Q switches all of that off.