Utsuroi: A Kyoto House You Walk Through by Scrolling, From First Light to Nightfall

Utsuroi (移ろい) is a Japanese word for the passing of things — the way a colour, a season, or a light changes while you are watching it. It is also the name of a small, astonishing open-source project by billpwchan that turns the word into a place you can visit: a house and garden in the hills north of Kyoto, rendered live in your browser, walked from first light to last.

Live site: https://utsuroi.billpwchan.art/
Source: https://github.com/billpwchan/utsuroi

Scroll is the clock

There is no play button and no video. You scroll, and the day passes.

One continuous camera path links fourteen resting places: the gate before dawn, the dewy path, the genkan entrance, the irigawa corridor, the zashiki, the tea room, the bridge at noon, the hearth, the engawa veranda, the dry garden, the bedroom, the bath at dusk, the night garden, and finally the house plan seen from above. Between two stops the sun moves on — and if you stop scrolling, the light keeps moving anyway. The sun follows Kyoto's actual sky from 04:45 to 21:00, and the lamps light themselves as it sets.

How the light works

The trick that makes it feel real is that the light is not faked in real time. It is path-traced offline in Blender Cycles, baked, and then blended by the hour as the day progresses. On top of that base sit scanned, real objects — stones, trees, lanterns and bowls captured by photogrammetry — and a house built in code on the old Kyoto module system.

The whole thing runs on three.js (r186) over WebGL2, with a render-scale governor that holds 60 frames per second in a browser tab. Press 1–4 at any point and the same walk changes season: petals drift in spring, fireflies rise over the stream on summer nights, maples drop their leaves in autumn, and in winter snow settles on the roofs and lanterns while the koi go deep. The timetable never changes, so every season can be walked the same way.

Even the loading screen is considered: while the world loads, the house is drawn as an architect's plan at 1:250, generated from the same numbers the 3D world is built from. The last stop turns that plan into a map — pick a room and you are taken back to it. Sound is optional and entirely synthesised in the browser, nothing downloaded: wind, bamboo, the stream, a bush warbler at a spring dawn, cicadas through a summer day, bell crickets at night, and the creak of a nightingale floor under your feet.

Why this one stayed with me

Most "3D in the browser" demos are built to show off a renderer. This one is built to show off time. The technology — baked path-traced light, photogrammetry, a scroll-driven camera — is all in service of a single, quiet idea: a building is not a thing, it is a schedule of light. The same room at 06:00 and at 18:30 is two different rooms, and utsuroi makes you feel that in your scroll finger.

It is also a sign of where solo creative coding has arrived. The repository's topics include claude-code and ai-generated alongside threejs, glsl and photogrammetry — one person, working with AI tooling, shipping something that a small studio would have struggled to finish a few years ago. The code is MIT-licensed (see the repo for asset credits), the repo was created in October 2026, and it is still young — which makes the level of finish more impressive, not less.

Open the live site on the largest screen you have, scroll slowly, and stop somewhere around the engawa in late afternoon. That is the whole review, really: a website that rewards you for doing nothing, beautifully.

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Repo facts checked at writing time: github.com/billpwchan/utsuroi, created 2026-10-04, JavaScript/three.js r186, WebGL2 at 60 fps, code under MIT licence, live at utsuroi.billpwchan.art.

Written by Terry Note — airgrix.com