XR: sources and measurements

The research behind the xr skill and the two templates it ships (ci/godot/templates/xr_math.gd and xr_rig.gd), gathered on 2026-10-29. Checks ran headless on Godot 4.7.2 (standard build) with no headset and no XR runtime; tests/Test-Xr.ps1 repeats them.

Sources

Source	What it gave
Godot manual, `tutorials/xr` (the `godotengine/godot-docs` repository, master branch, read as files: the documentation site did not resolve from this session)	Setting up XR, the better start script, room scale, basic locomotion, the action map, hand tracking, AR passthrough, XR Tools; every "the manual says" in the skill
Godot 4.7.2 `ClassDB` and `ProjectSettings`, read by `tests/xr-fixture`	Every class, property, method, signal and constant the skill names; `XRServer.primary_interface` null, OpenXR registered but not initialized, `xr/openxr/*` settings
GodotVR/godot-xr-tools, shallow clone of the default branch	MIT code, CC0 images and hand models (`LICENSE`, `hands/License.md`), `plugin.cfg` version 4.6.0, the scenes it provides, `velocity_samples` 5 in `function_pickup.gd`, snap turn defaults (20 degrees, 0.2 s), the vignette's properties
Half-Life: Alyx developer commentary, as `docs/valve.md` section 7 quotes it (items 53 to 58; checked word for word against the fan-wiki transcript on 2026-10-22)	The vehicle window, not moving the player for a character, the AI's breadcrumb trail, the peak of the last ten frames for throws, the generous catch range, one-controller play changing "controller bindings to game logic to level design"

Measurements (Godot 4.7.2, no headset)

What	Result
`XRServer.primary_interface`, `XRServer.world_scale`, interfaces listed	null, 1.0, "Native mobile" and "OpenXR"
`XRServer.find_interface("OpenXR")` then `is_initialized()`	found; false
`XRController3D` with no tracker: `get_has_tracking_data()`, `is_button_pressed()`, `get_float()`	false, false, 0
A tracker added with `XRServer.add_tracker()` and `set_pose()`	The `XRController3D` of that `tracker` name moves to the pose within a frame and `get_pose().linear_velocity` returns the velocity; `invalidate_pose()` clears `get_has_tracking_data()`
`XROrigin3D.world_scale = 2` on the current origin	`XRServer.world_scale` is 2
`XRCamera3D`, `XRController3D` and the origin in a scene with no interface	Load and run; no errors
57 names the skill quotes	All exist in `ClassDB` or `ProjectSettings`. A made-up name fails the test by name

The numbers in xr_math.gd (turn angle 30 degrees, a vignette minimum radius of 0.35 that closes at once and opens after 0.5 s over 1 s, a blackout from 3 cm to 15 cm of gap) are the kit's own first guesses; the tests hold their shape, not their value. The "peak of the last ten frames" is Valve's; XR Tools' pickup averages 5 samples instead.

Not confirmed

Everything that needs a headset: tracking quality and latency, hand tracking on any runtime, passthrough, refresh-rate changes, foveation, the Android export, and whether any comfort number is right for players. They are in the roadmap's list of what was not run.
Whether Godot XR Tools works on Godot 4.7.2: its README table was read (4.5.x needs 4.4 at least), the add-on was not loaded.
The documentation site (docs.godotengine.org), the fan wiki with the Alyx commentary (combineoverwiki.net) and Road to VR did not resolve from this session, so the Alyx quotes are the ones docs/valve.md already holds, not re-read; the Valve items are cited by their number there.
Valve's published VR talks (not looked for beyond the commentary), and Meta's, Sony's and Valve's own comfort guidelines.
XROrigin3D.world_scale against XRServer.world_scale when the origin is not current, and how pose velocities scale with it.