---
phase: 10.1-setdisplayeyetohead-spike
plan: 02
subsystem: driver
tags: [openvr, SetDisplayEyeToHead, visual-verification, ipd, spike, lighthouse-console]

# Dependency graph
requires:
  - phase: 10.1-setdisplayeyetohead-spike
    provides: "eyetohead_set pipe command with config reading and SetDisplayEyeToHead call"
provides:
  - "Confirmed: sidecar can call SetDisplayEyeToHead for device 0 (HMD owned by lighthouse)"
  - "Confirmed: repeated calls produce live rendering changes (not one-shot)"
  - "Confirmed: rotation matrix caching eliminates tracking disruption after first call"
  - "GO decision for Phase 11 direct SetDisplayEyeToHead approach"
affects: [phase-11, phase-12, phase-13]

# Tech tracking
tech-stack:
  added: []
  patterns: [lighthouse-console-downloadconfig, rotation-matrix-caching, intrinsic-xyz-euler-convention]

key-files:
  created:
    - .planning/phases/10.1-setdisplayeyetohead-spike/10.1-FINDINGS.md
  modified:
    - src/driver/device_provider.h
    - src/driver/device_provider.cpp

key-decisions:
  - "GO decision: SetDisplayEyeToHead from sidecar works for device 0 -- Phase 11 proceeds with direct approach"
  - "Config reading via lighthouse_console.exe downloadconfig instead of stale lhr-* directory files"
  - "Cache rotation matrices to avoid repeated ~20s tracking disruptions from lighthouse_console USB connection"
  - "Intrinsic XYZ Euler convention matches VAP alignment code"

patterns-established:
  - "lighthouse_console.exe downloadconfig for live HMD config reading"
  - "Rotation matrix caching: first call reads config, subsequent calls reuse cached values"
  - "SetDisplayEyeToHead(0, left, right) from sidecar for lighthouse-owned HMD"

requirements-completed: [SPIKE-01, SPIKE-02, SPIKE-03]

# Metrics
duration: 15min
completed: 2026-03-24
---

# Phase 10.1 Plan 02: SetDisplayEyeToHead Visual Test Summary

**SetDisplayEyeToHead from sidecar confirmed working for lighthouse-owned HMD -- all three spike criteria PASS, GO decision for Phase 11**

## Performance

- **Duration:** ~15 min (including orchestrator checkpoint resolution with 5 bug fixes)
- **Started:** 2026-03-24T13:00:00Z
- **Completed:** 2026-03-24T13:39:15Z
- **Tasks:** 2
- **Files modified:** 3 (device_provider.h, device_provider.cpp, 10.1-FINDINGS.md)

## Accomplishments
- Deployed driver, tested eyetohead_set command against live SteamVR with Beyond 2 HMD
- Confirmed SetDisplayEyeToHead from sidecar changes rendered eye separation for device 0 (HMD owned by lighthouse)
- Confirmed repeated calls produce live rendering changes with cached rotation matrices (instant after first call)
- Validated Euler angle decomposition with intrinsic XYZ convention
- Documented all findings with GO decision for Phase 11

## Task Commits

Each task was committed atomically:

1. **Task 1: Deploy driver and run initial pipe command test** - `b6e7e5f` (docs)
   - Also includes 5 bug fix commits from testing:
     - `01e37d8` - CLI allowlist fix
     - `bb6b623` - JSON parser multi-line fix
     - `60db6cc` - Euler convention fix (intrinsic XYZ)
     - `8e5cf67` - Config reading via lighthouse_console
     - `32008b1` - Rotation matrix caching
2. **Task 2: Visual verification in HMD and go/no-go decision** - (human checkpoint, approved by user, results recorded in FINDINGS.md commit `b6e7e5f`)

## Files Created/Modified
- `.planning/phases/10.1-setdisplayeyetohead-spike/10.1-FINDINGS.md` - Complete spike findings with SPIKE-01/02/03 results and GO decision
- `src/driver/device_provider.h` - Bug fixes during testing (CLI allowlist, caching declarations)
- `src/driver/device_provider.cpp` - Bug fixes during testing (JSON parser, Euler convention, config reading, caching)

## Decisions Made
- GO decision for Phase 11: SetDisplayEyeToHead from sidecar works, proceed with direct approach
- Config must be read via lighthouse_console.exe downloadconfig (stale lhr-* directory files are unreliable)
- Rotation matrices must be cached after first read to avoid ~20s tracking disruptions
- Intrinsic XYZ Euler convention is correct (matches VAP alignment code)

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 3 - Blocking] CLI allowlist missing eyetohead_set command**
- **Found during:** Task 1 (deployment and testing)
- **Issue:** beyond_prox_ctl.exe rejected eyetohead_set as unknown command
- **Fix:** Added eyetohead_set to CLI command allowlist
- **Files modified:** src/driver/device_provider.cpp
- **Committed in:** `01e37d8`

**2. [Rule 1 - Bug] JSON parser could not handle pretty-printed multi-line format**
- **Found during:** Task 1 (deployment and testing)
- **Issue:** lighthouse_console.exe downloadconfig outputs pretty-printed JSON; parser expected single-line
- **Fix:** Rewrote ParseEyeToHead3x3 for multi-line JSON parsing
- **Files modified:** src/driver/device_provider.cpp
- **Committed in:** `bb6b623`

**3. [Rule 1 - Bug] Euler decomposition used wrong convention**
- **Found during:** Task 1 (deployment and testing)
- **Issue:** Used extrinsic xyz instead of intrinsic XYZ convention, producing incorrect angle values
- **Fix:** Corrected to intrinsic XYZ convention matching VAP alignment code
- **Files modified:** src/driver/device_provider.cpp
- **Committed in:** `60db6cc`

**4. [Rule 1 - Bug] Config reading used stale lhr-* directory files**
- **Found during:** Task 1 (deployment and testing)
- **Issue:** lhr-* directory files may be stale; lighthouse_console.exe downloadconfig gives live config
- **Fix:** Changed config source to lighthouse_console.exe downloadconfig
- **Files modified:** src/driver/device_provider.cpp, src/driver/device_provider.h
- **Committed in:** `8e5cf67`

**5. [Rule 1 - Bug] Each eyetohead_set call spawned lighthouse_console causing ~20s tracking loss**
- **Found during:** Task 1 (deployment and testing)
- **Issue:** lighthouse_console.exe USB connection causes ~20 seconds of tracking disruption per call
- **Fix:** Cache rotation matrices after first read; subsequent calls reuse cached values
- **Files modified:** src/driver/device_provider.cpp, src/driver/device_provider.h
- **Committed in:** `32008b1`

---

**Total deviations:** 5 auto-fixed (1 blocking, 4 bugs)
**Impact on plan:** All fixes necessary for correct operation. No scope creep. Caching fix critical for usability.

## Issues Encountered
- First eyetohead_set call after driver startup causes ~20s tracking disruption due to lighthouse_console.exe USB connection. Mitigated by caching rotation matrices. Phase 11 should consider pre-reading config at driver init.
- Observed Euler yaw values (~2 degrees) differ from initially expected ~6.17 degrees. The ~6.17 estimate was rough; actual lighthouse config encodes ~2 deg yaw and ~5 deg pitch, which are correct.

## User Setup Required

None - no external service configuration required.

## Next Phase Readiness
- Phase 11 GO: SetDisplayEyeToHead from sidecar confirmed working for device 0
- eyetohead_set command from this spike serves as prototype for Phase 11's ipd command
- Key patterns established: lighthouse_console downloadconfig, rotation caching, intrinsic XYZ Euler
- Phase 12 still needs alternative UI approach (SteamVR slider trigger unresolved from Phase 10 FEAS-03)
- Consider pre-reading lighthouse config at driver init to avoid first-call tracking disruption

## Self-Check: PASSED

- [x] 10.1-FINDINGS.md exists
- [x] 10.1-02-SUMMARY.md exists
- [x] Commit b6e7e5f found (FINDINGS.md)
- [x] Commit 01e37d8 found (CLI allowlist fix)
- [x] Commit bb6b623 found (JSON parser fix)
- [x] Commit 60db6cc found (Euler convention fix)
- [x] Commit 8e5cf67 found (config reading fix)
- [x] Commit 32008b1 found (rotation caching fix)

---
*Phase: 10.1-setdisplayeyetohead-spike*
*Completed: 2026-03-24*