Daniel LynchandClaude Opus 4.8
b0503eedb6
Consolidate the two inline notes into one prominent note at the top of the doc, so the "this stub approach was not carried into the project" framing is seen before any of the entitlement-stub passages rather than only beside them. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01D6sFYGXZPsq3v7xtcDES6g
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.