Proposal: SpAItial Echo-3 world-model captures in glasses-free 3D (Streamed SOG dollhouse in the DisplayXR Browser)

[joehillthunder]

Summary

SpAItial's Echo-3 (released 2026-10-27) is a world model that rebuilds a real space from a few minutes of iPhone video as a metric-scale 3D Gaussian splat world. It has no XR mode of its own, so it fits the content class (like generated 3D, #2391): no new viewer, the worlds go into the DisplayXR Browser's existing woven splat tile. A working demo is live:

https://joehillthunder.github.io/displayxr-demos/apps/echo-worlds/ (any browser shows 2D; the DisplayXR Browser on a 3D display shows 3D)

What it does

• Six worlds from SpAItial's public Echo-3 gallery (a playroom, a robotics workshop, a two-storey house, a vaulted hall, a game room, a library), streamed from the owner's CDN as Streamed SOG (lod-meta.json, ~10 M splats, 3 LOD levels, CORS open), credited on the page, nothing redistributed.
• Dollhouse view by default. These are inside-out captures: opened at their capture camera the viewer is inside the room, which breaks "subject fully in view at a middle size". The page cuts each room 1.6 m above its floor (setEffect('clip', { box })), frames the cut room from outside, looks down 35° and turns it slowly. "Dollhouse" toggles the cut.
• Measure in metres (two picks + a line): the worlds are metric, so a 3D display can show true dimensions.
• Depth −/+ (50–150 %, 25 % steps) and Reset, Full panel as an explicit button; windowed by default, one persistent woven canvas, covered until firstWoven.
• One inline-3D tile: addSplat(…, { engine: 'playcanvas', rig: 'display', flipY: false }), ~600 k splats resident under the SDK's default Streamed SOG budget.

Measurements (runtime 2.57.1, Leia SR plug-in 2.19.1, DisplayXR Browser 156.0.8078.12, the tested display 344 × 215 mm)

• Woven: batch weave … eyes_valid=1 flat=0, firstWoven resolved; ~380–400 k splats resident per tile after streaming (handle.stats()).
• Framing (2D captures): Robotics Workshop and Game Room render upright, cut, and fully in view at rest.
• Depth %: not measured: the Browser doesn't consume the runtime's atlas trigger (as for the NuRec splat in COMPAT). Seated check pending, reported as Pass/Fail at 100 %.

Findings worth folding into the SDK / content contract

1. Up axis is not in the file. Echo-3 worlds are Y-up (floor ≈ 1.5 m below the first camera); most 3DGS exports are Y-down, so the SDK's default flipY: true renders every room upside down. A splat-transform / SOG meta.json field for the up axis, read by addSplat, would remove the guess.
2. frame is not honoured on a Streamed SOG. The display rig framed from octree leaf boxes and orbited a default focus ([0, 0, 2]), putting the room off-centre and overflowing the tile. Calling viewer.fitTo(center, extent) + setFocus(center) after ready fixes it.
3. The fit box is measured unpitched. At a 35° rest pitch the cut room projects taller than the box and overflowed; the page rests at zoom 0.75. A pitch-aware fit (fit the box as posed) would let room-scale content default correctly.
4. Room-scale captures need a cut-away by default. A small offline pass over the coarsest LOD (floor = lowest dense height slab, footprint from 2–98 % quantiles) gives a clip box per world in seconds; the same rule should apply to any scanned interior (real-estate, digital-twin captures).

What a shared host / content library would need

• Splat metadata: up axis, metric scale flag, and a baked "subject" box (or floor + footprint for interiors) in the SOG / Streamed SOG meta.json.
• The comfort budget from display info (Display info: publish the comfort budget (front/behind disparity limits), e.g. layout.comfort {front_frac, behind_frac} #2388, Proposal: what 21 app integrations need from the shared host library (comfort budget in display info, texture hand-off per API, and a map of every per-app post) #2442), so the depth control's 100 % means the budget on every display.

Open items

• Seated depth check on the panel (Pass/Fail at 100 %; then adjust the 0.75 rest zoom or the 1.6 m cut if needed).
• Public-use terms for the gallery captures (credited and streamed today).
• A user's own Echo-3 export (SOG/SPZ) by URL or file drop.

🤖 Generated with Claude Code

[joehillthunder]

Seated check: PASS

• Conditions: runtime 2.57.1 + Leia SR plug-in 2.19.1, DisplayXR Browser 156.0.8078.12, the tested display (344 × 215 mm). Robotics Workshop in the windowed tile, beside other apps.
• First look: at the SDK display rig's default depth, framing and look passed, but depth read too strong. Depth: Fail.
• Fix: the page's 100 % is now 0.75× the display rig default (?depthBase= overrides); −/+ still steps 50–150 %.
• Result: at the new 100 %, Pass.
• Not measured: depth %, because the Browser doesn't consume the atlas trigger.
• Note: a fixed 0.75 is a per-page constant. With the comfort budget in display info (Display info: publish the comfort budget (front/behind disparity limits), e.g. layout.comfort {front_frac, behind_frac} #2388), the default could be fitted to the budget instead.

🤖 Generated with Claude Code