Daniel LynchandClaude Opus 4.8
a72a79ad29
An independent reimplementation of Meta's libOVRPlugin ABI on top of OpenXR, so VrApi-era Meta Quest VR titles can run on non-Meta OpenXR runtimes (Monado, Steam Frame) instead of being locked to Meta hardware. Original code only — no Meta/Epic/Capcom binaries, headers, or assets. Includes a desktop harness that drives the shim against Monado headless. Scope/legal: interoperability; entitlement handling is out of scope. See README for the legal/scope section and docs/ for the research trail and design notes. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01D6sFYGXZPsq3v7xtcDES6g
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RE4 VR shim — docs
Research trail and session handoffs for the OVRPlugin→OpenXR shim that runs RE4 VR on non-Meta OpenXR runtimes (Quest 2 today; Steam Frame the goal).
handoffs/— chronological session handoffs (the day-by-day journey).research/— reverse-engineering notes, design docs, the ghost-fix writeup, andrelated-work.md(how Overport/others run Quest games elsewhere; why this shim is novel).../analysis/— raw RE dumps (*.txt, mostly gitignored;all_exports.txt+shim_surface.txtfeedshim/gen_stubs.sh).- Operational docs live at repo root:
README.md,TESTING.md,HOST.md.
The "ghost" — how it was actually solved (the short version)
For weeks the headline bug was a VR "ghost": doubled/tripled hands and watches, seated-mode deform, standing-mode black flashes. It survived every theory it looked like — stereo geometry, FOV/IPD, depth reprojection, render-submit ordering, GPU load.
The break came from building P4 passthru (research/ghost-fix-2026-06-27.md):
running the real Meta libOVRPlugin inside our app proved native is flawless, so the
bug was in our path. Then always-on anomaly logging caught the real signature —
dropped frames — and a recording + frame-blending showed it was whole-frame
temporal judder, not a stereo/geometry artifact. Localizing the stall showed UE's
render thread blocking ~85–150ms during motion at only ~14ms of GPU work.
Root cause: the shim left ovrp_WaitToBeginFrame a no-op and ran xrWaitFrame on
the render thread, so the game thread was unpaced and UE's pipelined renderer
desynced → render-thread stalls → dropped frames → the compositor's timewarp filled the
gaps → judder. Fix: pace the game thread like vrapi (xrWaitFrame in
xrr_wait_frame, frameState handed to the render thread via a 1:1 FIFO ring). Result:
render stall 150→3ms, drops 0.79% (~native 0.34%), steady 72Hz — ghost gone.
Commits 79476c3 (fix) + c0ecff3 (XR_FRAME_DISCARDED guard).
Secondary wins kept as defaults: game-driven FFR (apply the game's foveation), and the per-frame luma readback off.
Reading order if you're new
research/ghost-fix-2026-06-27.md— the full diagnosis chain (start here).handoffs/newest → oldest — the journey, including the dead ends (reproject, submit-ordering, depth) that were ruled out.research/RECON.md,RE-NOTES.md,SHIM-SCOPE.md— how the shim was reverse-engineered.research/render-submit-sync-design.md— the render/submit sync design.