Inferred building interiors

World explorer enables lazy interiors in the styled Human layer: choose Walk, approach a building, and walk through its framed entrance. Near the entrance, the windows become transparent and reveal the same interior you can enter.

?interiors=0 disables this capability. ?synthetic=1&stores=1 provides a repeatable block of recognizable stores; test/visual/interiors.play.json walks into and out of its fast-food restaurant and grocery store. Use ?synthetic=1&houses=1 for a residential block with two-storey houses and a bungalow. test/visual/houses.play.json walks through its entrance, climbs the stairs, and enters a bedroom.

These layouts are plausible procedural interpretations of building use, not surveyed floor plans. Confirmed occupant categories take precedence over building labels, then surrounding use. The selected exterior style supplies a final fallback hint, so weakly labeled homes receive a domestic layout. Unrecognized uses receive a generic furnished hall. A multi-tenant building currently uses one inferred ground-floor program; it does not infer individual leased premises.

Reusable generation platform

The implementation lives in @bendyline/molen-worldgen/kernel and knows only metric polygons, opaque identities and use labels. The Earth adapter supplies those labels from mapped businesses without changing the exterior classification of towers. Source feature identities, or the existing quantized location identity when absent, stabilize the result.

The interior catalog is content: the style pack names it ("interiors" in stylepack.json) and the resolved pack carries it as pack.interiors. A pack without one generates no interiors.

1. generateBuilding({ ..., interiors: catalog }, builder) cuts a real entrance and frontage windows into the exterior. Homes also have bounded side/rear and upper-storey apertures. Its record.interior is an InteriorSite: canonical outline and courtyard holes, floor and ceiling, door/window apertures, access ramp, available storey heights, labels and identity. This stage generates no floor plan or furniture.
2. generateInteriorPlan(site, { catalog }) returns a data-only InteriorPlan: rooms, fixtures, storeys, stair runs, reserved circulation strips, seed and work statistics.
3. generateInteriorGeometry(plan, catalog) produces structure, furniture, glass, visible stair-step and smooth stair-collision buffers. Structure includes floors, ceiling, interior-facing shell walls, room partitions with doorways, and an entrance ramp. Furniture is a merged vertex-color batch of structured low-poly models: stocked shelving, racks, counters/registers, tables/chairs, beds, desks, sofas and benches, plus fitted kitchens, bathroom fixtures, wardrobes, dressers, bookcases, rugs, coffee tables and plants.

import {
  generateInteriorPlan, generateInteriorGeometry, validateInteriorCatalog,
} from '@bendyline/molen-worldgen/kernel';

const catalog = pack.interiors ?? validateInteriorCatalog(myCatalogJson);
const plan = generateInteriorPlan(site, { catalog, maxFixtures: 160, maxCandidates: 1024 });
const buffers = generateInteriorGeometry(plan, catalog);

Both generation passes have *Steps variants that yield repeatedly. They run without a DOM or three.js and can also be driven by a worker host. The shipped client drives these iterators cooperatively on the main thread; exterior generation continues through the existing worker.

Data-driven profiles and algorithms

molen/interior-catalog@1 is a registered JSON format. Validate it with molen validate catalog.json; discover its fields with molen schema get interior-catalog. The default style pack's interiors/catalog.json (in the molen.worldgen.default content pack, source content/worldgen/interiors/) is a complete editable starting catalog with 15 profiles:

Program	Algorithm and furnishings
Grocery	Long stocked shelf rows, 2.4 m aisles, front checkout
Fast food, restaurant, cafe	Tables and chairs with an entrance-side service counter
Pharmacy, retail, library	Smaller shelving modules and generous access strips
House	Connected hallway, living room, kitchen, bathrooms, bedrooms, and stairs to an upper floor when it fits
Apartments/hotel	Repeated room pods off circulation spaces
Office	Desk and chair modules with clear routes
School	Larger room pods with desks
Clinic	Room pods with beds
Warehouse	Tall storage racks and 3 m handling aisles
Assembly	Bench rows with a central aisle
Generic	Furnished hall with seating

Each profile supplies an id/version, ordered label matches, algorithm family, furniture type, module dimensions, aisle width, placement density and floor/wall/wood/accent colors. Catalog validation rejects duplicate ids, missing fallbacks, invalid colors and unsafe metric ranges. The seven reusable layout families are aisles, dining, rooms, workplace, storage, hall, and residential. Add or tune a profile in JSON to vary these families; extend the typed algorithm union and generator when a new topology is necessary. The optional residential profile settings control whether upstairs is allowed, clear stair width, run per meter of rise, and minimum room width.

The seed is interior1|<identity>|<profile.id>@<profile.version>. Named coordinate draws make placements independent of request order, frame timing, floating-origin shifts and unrelated profile edits. Smaller fixture caps preserve the prefix of the full layout. A profile version bump intentionally rerolls that profile. No global random state is consumed.

Placement reserves the entrance spine, front circulation and cross aisles before furnishing. Whole-rectangle tests include polygon edges and enclosed courtyard holes, so checking only corners cannot accidentally place furniture across a concavity. Room furniture sits at the back, leaving the doorway and turning space clear. Conservative placement can leave irregular wings sparsely furnished; the generated floor still follows the complete outline and holes.

Residential rooms and stairs

The residential algorithm fits two banks of rooms beside an entrance-connected hallway, then assigns domestic uses instead of repeating beds. Single-storey homes get living, kitchen, bedroom and bathroom spaces. When the envelope and footprint fit a safe stair run and a 1.5 m landing, bedrooms move upstairs. Room records carry a purpose, storey index and hall-facing 1.16 m doorway. Partitions include headers, door casing and skirting; fixtures reserve turning space at each door. House identity determines room proportions, bedding size, upholstery and decor colors. Kitchens include cupboards, worktops, a sink/faucet, hob and oven. Bathrooms have a shower, toilet and vanity. Furniture remains deliberately low-poly.

This first vertical topology supports ground plus one upper floor. Stair rise is divided into steps no higher than 18 cm, with a default horizontal run of 1.65 m per meter of rise. The run is removed from both the lower ceiling and upper floor. Guard walls and handrail trim protect the upper opening; the landing leads directly back to the hallway. Insufficient width, depth or headroom produces a single usable floor, rather than inaccessible upstairs rooms. Irregular wings retain conservative placement and can remain sparsely furnished.

Streaming, rendering and collision

InteriorStreamer from @bendyline/molen-worldgen/client accepts groups of sites and a metric origin. Call register(root, sites, [originX, originZ]) after creating a region's exterior, update([cameraX, cameraY, cameraZ]) before collision, and unregister(root) on disposal. The supplied root must be attached to a visible scene hierarchy.

new InteriorStreamer({ catalog }) takes the same catalog. The Earth renderer wires registration/disposal automatically when created with interiors: true or streaming options, using the style pack's catalog (and generating no interiors when the pack has none). The host calls renderers.updateInteriors(cameraPosition) each frame. Only complete buildings at the finest semantic level receive sites; coarse representations retain the cheap exterior path.

Defaults are a 65 m load distance, 90 m release distance, 12 resident interiors and a 16 MiB resident geometry cap. Distance is measured to the footprint (including courtyard boundaries) and vertically to the available storey envelope, so a large building remains resident while you are inside and a high fly camera does not request rooms underneath it. Selection checks region bounds, then prioritizes nearby buildings and deduplicates source identities. Plans cap at 1,024 candidate modules and 160 fixtures (hard ceilings 4,096 and 512). The work budget is 3 ms and 64 iterator steps per frame, with at most one completed upload per frame. This is a cooperative budget, not a hard deadline: triangulation and final buffer upload are indivisible operations.

One opaque portal batch covers unready entrances/windows per region. Publication attaches the complete interior and removes those covers atomically. Eviction restores covers and disposes owned geometry; shared materials survive until streamer disposal. Hidden layers, region disposal and moving out of range cancel pending work. There is no unbounded interior cache: returning regenerates the same plan. Cached exterior descriptors count toward the existing tile cache budget. The HUD reports available/resident interiors, pending generation, memory and failures.

Structure, furnishings and glass share materials across interiors. Four shared 256² detail maps supply wood grain/boards, ceramic grout, fabric weave and plaster grain, using metric UVs and mipmaps. These neutral maps combine with household vertex colors; no texture is allocated per building. Their fixed shared memory is separate from the resident geometry counter. Furniture is merged instead of spawning one scene object per shelf product. Ceilings use simple bright fixture geometry; there are no per-building dynamic lights or additional shadow maps. The walking octree uses the same published geometry, except that visible stair steps are skipped (walkIgnore) and a closed wedge supplies smooth stair collision. The published proxy is marked walkCollisionOnly and has rendering layers disabled. Hosts using the kernel buffers directly should likewise omit steps from physics and add collision to their collision scene. Portal index changes invalidate collision, and window glass is solid from either side. Doorways remain open without an interaction key or door animation.

Current limits and next extensions

This release covers ground floors and a connected upper floor for suitable homes in complete, non-elevated polygon buildings that fit the exterior geometry budget and have room for human-scale access. It does not promise entry into every mapped fragment: clipped footprints, elevated parts, very low/narrow structures, budget-boxed and omitted buildings lack a site. Additional storeys, switchback stairs, elevators, animated doors, tenant subdivision and persistent object edits remain future extensions.

Ground-floor platforms use the highest sampled perimeter height and an entrance ramp. Very steep sites, terrain protruding inside a large footprint, adjacent buildings obstructing a door, or missing street-access metadata can still need a site-specific access solution. Window transparency applies to generated apertures; homes have upper windows where the envelope allows them. An aperture above an unused storey stays backed by an opaque surface. Interior objects are viewer-local geometry, not persistent ECS entities. Extend the plan contract with gameplay state before allowing movable furnishings.

Regression coverage includes every profile, deterministic regeneration, translated origins, courtyard/concave containment, work/memory caps, streaming cleanup, and walking through the actual shell both before and after publication, plus ascending stairs, entering an upstairs bedroom, descending and exiting with the real capsule controller. The browser playback scenario checks the visible world-view path alongside those headless checks.