Kiln: a procedural 3D asset engine

How it works

A recipe in, an asset out

Each kind of thing has a generator, a Python module: doors, windows, trees, seating, buildings, towns, characters. Each asset is a registry entry, a JSON recipe that names its generator and pins every parameter. A new oak is a new entry; a new kind of thing is a new generator. The catalogue grows by adding entries to the registry, not by modelling.

Left: the JSON recipe for a slat chair, with its generator, seed and every dimension. Right: the chair Kiln builds from it, with its triangle count, size and SHA-256 fingerprint — **The real registry entry for a slat chair, and what `kiln make` builds from it.** Width, depth, leg count, splay, slats and wood colours are all explicit parameters; nothing falls back to a default.

Define the recipe
A JSON entry names a generator, a seed and every parameter. There are no default values anywhere: a missing parameter is an error, not a guess, so the recipe fully specifies its asset and diffs and versions like code.
Build
The generator emits geometry, materials, skeleton and animation clips as a .glb, plus a sidecar recording triangle count, bounds, node and clip names, a SHA-256 content hash and the licence.
Compose by reference
Doors, windows and wall panels are assets in their own right. Buildings reference them and towns instance the buildings. Change the door, and every house that uses it rebuilds with it.
Validate in Godot
Every asset goes through Godot’s own glTF importer and is measured: bounds, meshes, skeleton, clips. It passes only if the engine agrees with the sidecar.
Render and review
Kiln renders its own output: turntables from the game’s camera angles at on-screen size, animations sampled frame by frame, and lineups of whole sets.
Deliver
One command ships finished assets to a game’s inbox under a versioned contract (units, scale, budgets, bone and clip names), with the licence and hash of every file.

Composition

Components, then buildings, then towns

A building generator assembles walls, doors, windows, stairs and chimneys, and furnishes its rooms from the furniture generators. A town generator lays out streets, a square, back lanes and gardens, and places the buildings, wells, market stalls, lamps and trees. Shared parts are stored once: a window reused two hundred times in a town is one mesh.

Left: doors, windows, wall panels and a staircase. Middle: a timber-framed house assembled from them. Right: a town laid out from such houses, props and trees — **Small things build big things.** Components, a building assembled and furnished from them, and a town laid out from buildings, props and trees.

A row of generated building components: door frames, wall panels, doors, shuttered windows and a staircase — **The parts.** Each door, window, panel and stair is its own registry entry.

Variety

One recipe, many results

Change the seed and the same town recipe yields a different town: other streets, other houses on other plots, a new market square. Change one number and a chair becomes a stool. Variety comes from shape, size and colour, not only from a reshuffled seed.

Three different generated towns, labelled seed 2, seed 3 and seed 4 — **Same recipe, three seeds, three towns.**

Six generated houses: gable, hip, thatch, two-storey, jettied and wide hip roofs — **One generator, six houses.** Gable, hip and thatch roofs, one or two storeys, a jettied upper floor.

A row of generated trees: oaks in four seasons, pines and bare dead trees — **A forest of seeds.** One tree generator: oaks in four seasons, pines, dead snags.

Reproducible

The same bytes, every time

All randomness comes from named, seeded streams (FNV-1a), so a recipe always produces the same bytes. Each recipe also pins the SHA-256 hash of the asset it makes. When Kiln changes, drift detection rebuilds and re-hashes every asset and names any that moved, so a week spent on the tree generator provably leaves every house unchanged.

When a generator gains a parameter, every existing recipe is retrofitted with the value that reproduces it exactly. Old assets never drift.

A terminal: Kiln builds the slat chair twice and gets the identical SHA-256 fingerprint, then a changed recipe gives a new stool — **Built twice, same fingerprint.** Change the recipe and you get a different, equally reproducible asset.

Buildings

Real places, inside and out

Shapes and storeys. Rectangles, L and T wings and lean-tos, one storey or several, with jettied upper floors on their posts and beams.
Roofs and walls. Gable, hip, thatch, lean-to and battlemented flat roofs; timber frame, coursed stone and plank walls, with windows, shutters, flower boxes and studded doors set into their openings.
Interiors furnished by purpose. Taprooms, bedrooms, smithies, a chapel with pews either side of an aisle. Stairs and ladders lead to upper floors you can walk; hatches lead down to cellars of barrels and sacks.
Ready for a game. Each building reports its floor plan: walls, doors, rooms, walkable cells, stairs, and the parts to hide when the player steps inside.

A timber-framed inn with its roof removed: an upper floor with two beds, a chest, shelves and a stair opening — **The inn, roof lifted.** Beds, a chest, a shelf and the stairwell down.

The inn's stone ground floor from above: hearth, bar, stairs and a cellar hatch — **The taproom below.** Hearth, bar, stair and the hatch to the cellar.

Twelve generated buildings at true scale, including a guardhouse, cottage, chapel, tower, barn, windmill, smithy, inn and a ruined house — **Kinds of building, at true scale.** Guardhouse, cottage, jettied house, chapel, tower, barn, mill, shop, smithy, T-house, inn and a ruin whose fallen walls still leave every room reachable.

In motion

Assets that move

Assets carry their own animation: doors open, chests open and can be left looted, lanterns flicker, the well bucket sways, chimneys smoke, fountains spray and the mill’s sails turn. Characters share one skeleton, so every motion works on every body.

The inn turning a full circle — The inn on Kiln’s turntable

A windmill with its sails turning — The mill’s sails

A stone fountain spraying water — The fountain: droplets on parabolas

A hooded archer running, the cloak flaring behind — A run cycle; the cloak swings on its own bone

Towns, wilds and the small things

Everything in its place

Between towns, a wilds generator lays out streams with fords and stepping stones, standing stones, ruins, camps and barrows. Every placeable thing carries tags for what it is for and where it may stand, and Kiln refuses to put anything where it doesn’t belong: you won’t find a signpost in a cellar.

The furniture and props get the same care as the buildings: chairs, beds, cupboards, shelves of books and jars, anvils, cauldrons, hearths, candles, tankards, chests, barrels and sacks, each from its own generator, each with its states.

Generated street props: a lamp post, a well, a spraying fountain, a signpost, a glowing waystone, a market stall, a campfire and a tent — **Street and camp.** Lamp post, well, fountain, signpost, waystone, market stall, campfire, tent.

A low-poly supper table on a red rug with a slat chair, stool, candle, bread, tankards, books, jugs and an oak barrel — **Small things, made with care.** Every piece is its own generator.

Generated furniture: a four-poster bed, wardrobe, bookshelf, workbench, cauldron, brazier, hearth, bench and table — **Furniture.** Rooms are furnished from these by what each room is for.

Crates, barrels, chests and sacks, each shown closed and then looted — **States.** Each container shut, then looted: lids askew, a barrel head leaning on its side, sacks slumped.

Characters

Bodies, garments and motion

Bodies from sliders: sex, age, height, weight, build and ancestry. A species layer reshapes ears, noses, brows and proportions for hobgoblins and orcs.
Garments that fit every body: tunics, robes, kirtles, hoods and cloaks, woven from generated cloth, including linen with a real weave, felted wool, leather and mail of linked rings. Any garment can be re-dyed in madder, woad, weld, walnut and more.
Items on a shared grip: swords, axes, clubs, bows, shields and helms, so any hand can hold any weapon.
Motion on one skeleton: idle, walk, run, attack, block, cast, roll, sit, talk, drink and more, shared by every character. An archer can be aimed: it turns side-on and draws to the cheek.
Populaces from one recipe: give ranges and choices, and Kiln expands them into a crowd of distinct, dressed, named townsfolk. Each is seeded by name, so adding one person never changes another.

Three generated fighters in action: a mailed swordsman with a shield, a bearded axeman and a hooded archer drawing a bow — **Three fighters, one skeleton.** A lunge, a swing and a draw.

A crowd of generated townsfolk in dyed tunics, robes and kirtles, each with a different body, face and hair — **A town’s people from one recipe.** Nineteen distinct folk, every body, outfit and dye drawn from ranges.

Green-skinned hobgoblins with axes and clubs around a horned, red-caped chief mid-swing — **The species layer.** Hobgoblins and their chief, on the same bodies and skeleton as everyone else.

Creatures built from Kiln's own primitive generators: a warrior, a chief, a shambler, a wight, a hound, a rat and a carter — **Built from primitives.** Creatures and the undead from Kiln’s own figure and beast generators, animated in the recipe.

The same armoured character in eight poses: idle, run, thrust, block, cut, throw, roll and fall — **One skeleton, every motion.** Idle, run, thrust, block, cut, throw, roll, fall.

Sound

Music from recipes too

Kiln also composes and renders music. Instruments are JSON recipes; themes are melodies with their harmony; pieces are built from themes, with sections in different keys, development and variation. It writes long-form town music that keeps changing for eight minutes and more without repeating, and each piece can carry a combat layer that plays in step with it. Everything renders to WAV or Ogg, reproducible to the byte like the models.

Built for production

Budgets, speed and provenance

Budgets. Every asset type has a triangle, texture and bone budget; characters are decimated to fit.
Fast iteration. A build cache rebuilds only what a change touches: the asset whose recipe changed, the generator whose code changed, and everything that uses them. Most rebuilds finish in seconds.
Provenance in every file. Each asset records its generator and version, seed, inputs and their licences, and the tools that built it. A game’s credits page can be built from those records.
Standard output. glTF 2.0, which Godot, Blender, Unity and Unreal all read without a plug-in.

49generators

360+asset recipes

100+generated characters

50+garments and dyes

22buildings, furnished

36motions on one skeleton

16music pieces and combat layers

8days from first line to all of the above

Built with Python 3 · NumPy · glTF 2.0 · Godot 4 (validation and rendering) · Blender with MPFB · FNV-1a seeded streams · SHA-256 fingerprints · libsndfile and Ogg Vorbis. Buildings, props, trees, rocks, creatures and music are computed from scratch. Characters are built on open CC0 foundations: MakeHuman base bodies and garments, and Quaternius animation clips retargeted to Kiln’s skeleton.

Kiln is the 3D counterpart of TiGen, our 2D tile and sprite engine. Both are in-house tools and are not released.

A recipe in, an asset out

Define the recipe

Build

Compose by reference

Validate in Godot

Render and review

Deliver