Balloon

About this piece

A meadow ridge on Mount Norquay above Banff, late in September, with fresh snow on the peaks across the Bow Valley. You hold a balloon on a string while Everything You Do Is a Balloon plays through the afternoon. The sun lowers, the shadows stretch, and at the release the string slips and the balloon drifts away down the valley. The day runs on into night, and at dawn there is a new balloon and the song begins again.

Field notes

Drag anywhere to tug the string. The tape wow follows its tension, and the balloon answers the wind as well as your hand.

Make a fist to hold the string, open your hand to let go. Hand control is optional: turn on Hand in the scene toolbar and allow the camera, then move your hand to move the balloon; let go and it springs back to rest. The camera and the hand model load only after that click, and video is processed on your device; no frames leave it.

Touch the world to bring a part of the song forward: the grass is the pads, the swallows are the melody, the bicycle wheels are the chord stabs. Each touch swells for a moment, then lets go.

The wind is one system for everything. Gusts cross the meadow at random, bending the grass and the trees and moving the balloon, and the sound follows them. Gusts and the swallows improvise softly in the song's chord and on its beat.

There is no rewind and no end card. After the release the light goes, the town comes on below and the stars come out; a minute later the sun rises on the next day.

A real afternoon above Banff

The landscape is real. Elevation comes from AWS Terrain Tiles at three levels of detail: a 12-metre grid around the meadow, a 62-metre grid out to about 20 kilometres, and a one-kilometre grid to the horizon. Earth curvature, with a little atmospheric refraction, is baked into the heights, so the far ranges sit down behind the near ones as they do from the ridge.

OpenStreetMap gives the Bow River, the lakes and the town. Banff's 1,925 buildings are instanced from their real footprints with pitched roofs, and every one of them lights up after dark.

A single surface shader paints the whole valley from slope, aspect and elevation: tawny meadows, a few larches turning gold near treeline, and a late-September dusting of snow whose line sits lower on north faces than on south ones, lingers on ledges and in gullies, and slides off the steepest walls. A horizon map toward the sun lets the mountains shade one another as it lowers.

Trees, rocks, sky and birds

Engelmann spruce, subalpine fir and lodgepole pine are generated in the page from branch cards with needle textures drawn at load. Near trees are real geometry; the far forest is an impostor atlas, so the whole valley can be wooded. Weathered limestone boulders and outcrops are displaced in code too.

The sky shader carries an altocumulus deck that shadows itself toward the sun, a cirrus veil and the Belt of Venus at dusk. A cap cloud clings to Mount Rundle, with lit banks over the far ranges.

A boids flock of swallows wanders the visible sky, with a few solo birds peeling off. Their sharp turns become notes.

One wind

A single wind state drives everything: a prevailing direction and strength that wander slowly, patchy cat's-paws carried along by it, and gust fronts that arrive at random times from varying directions and roll across the meadow. The grass, the near trees, the far forest, the sheen on the meadow, the balloon and the sound all read the same wind, so what you see and what you hear agree. It calms into the evening.

The string is a Verlet rope and the balloon a buoyant body on its end. You hold it; the wind only pushes it gently. At the release it rides the valley wind and the evening drainage flow down toward the Bow, slowly losing height.

The song and what plays along

The song is performed live by a Web Audio synth in the page from a new transcription. Nothing is sampled.

Around it, a generative layer listens to the scene. The wind sets the level, colour and stereo position of the air; gust fronts can set off a soft two- or three-note phrase; swallow turns become short chirps and the flock's sharp turns become arpeggio fragments. Every note is drawn from the chord sounding at that moment and quantised to the song's beat, and the layer stays sparse, quieter while the melody is busy and only the wind at night.

A day that keeps going

The sun follows real late-September geometry for the ridge: across the song it falls from about 14° to just above the horizon. After the release the day runs on for about a minute, through dusk and a starry night over the town's lights to dawn in the east, when a new balloon arrives on its string and the song starts again. It loops for as long as you stay.

The image is graded like Super 8 film: halation, a warm reversal-stock grade, hexagonal lens ghosts, grain and a slight gate weave.

On a phone

Touch devices and small screens start in a lighter mode: pixel ratio capped at 1.5, a 1,024-pixel shadow map, about 26,000 grass blades instead of 120,000, a coarser terrain mesh, a smaller flock and no multisampling. A phone frame comes to roughly 530,000 triangles in under 90 draw calls. Quality can be changed in the settings.

In the details