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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
61 lines
3.3 KiB
Markdown
61 lines
3.3 KiB
Markdown
# OVRPlugin -> OpenXR shim — scope
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Derived 2026-06-23 from RE4 VR v2.3 (`com.Armature.VR4`). Method: extracted the
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distinct `ovrp_*` names `libUE4.so` references (dlsym targets) and intersected
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with `libOVRPlugin.so`'s exports. Raw lists in `analysis/`.
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## Headline numbers
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- OVRPlugin exports **438** `ovrp_*` entry points.
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- The game actually references **239** of them. That's the shim surface.
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- But **~150 of the 239 are stub-to-constant / no-op** for a basic port.
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Realistically **~85-90 functions need real implementation**, of which the
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genuinely hard core is **~40** (frame loop + layer/swapchain + the display
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interop).
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## Render API: VULKAN (confirmed)
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`libUE4.so` has VulkanRHI compiled in and calls `ovrp_Get{Instance,Device}ExtensionsVk`.
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libGLESv2/EGL are NEEDED but that's the standard Android baseline; the active
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renderer is Vulkan. => swapchain path is the standard **OpenXR `XR_KHR_vulkan_enable2`**
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(import the app's VkImages into `XrSwapchain`). Well-trodden, not exotic.
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## STUB to no-op/constant (~131 counted, +misc ≈ 150)
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| Group | count | how to stub |
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|---|---|---|
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| Mixed Reality Capture (`ovrp_Media_*`) | 37 | return not-initialized / no-op |
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| Camera device (passthrough/depth) | 21 | report unavailable |
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| External camera (MRC) | 13 | report 0 cameras |
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| Perf/GPU/CPU/ASW/foveation tuning | 31 | accept+ignore, return safe defaults |
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| Boundary / Guardian | 7 | "not configured" (or map to XR play bounds later) |
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| Hand tracking | 7 | disabled (RE4 VR is controller-only) |
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| System-info getters | 15 | return plausible constants (headset type, region…) |
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Stubbing these = ~150 functions for near-free. None affect core gameplay.
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## MUST implement (~88 counted; the project's real work)
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| Group | count | notes |
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|---|---|---|
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| Tracking / poses | 32 | mostly mechanical: map OpenXR `xrLocateSpace`/views to `ovrp` pose structs |
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| Display / layer / swapchain | 20 | THE HARD PART — projection layers, eye FOV, foveation, swapchain stages |
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| Input / controllers | 11 | map Touch controller -> OpenXR action set; mechanical but fiddly |
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| Eye / user params | 10 | IPD, eye height, pixels-per-tan-angle -> from XR view config |
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| Init / shutdown | 8 | session create/begin/end, instance+system setup |
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| Frame loop | 6 | `xrWaitFrame`/`xrBeginFrame`/`xrEndFrame` <-> `ovrp_*Frame4`, predicted display time |
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## Verdict
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Single-developer-feasible, meaty. The "239 functions" headline collapses to
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**~40 hard + ~45 mechanical + ~150 stubs.** The hard 40 are the standard guts of
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any OpenXR app (frame loop, projection layers, Vulkan swapchain, pose/input
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mapping). **Modern Meta OVRPlugin already ships an OpenXR backend** — that's the
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reference for exact `ovrp_*` semantics and struct layouts, which removes most of
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the guesswork.
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Biggest unknowns / next probes:
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1. Exact `ovrp_*` struct layouts/ABI (need OVR_Plugin.h matching this OVRPlugin
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version, or RE them in Ghidra). ABI mismatch = crashes.
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2. How the Java side loads libOVRPlugin (System.loadLibrary) — confirms the
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replacement mechanism (drop-in shim .so with same SONAME).
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3. Entitlement: out of scope for this project — no `ovr_*` replacement ships here;
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the platform's real check runs unchanged (see README "Legal / scope").
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4. Whether Steam Frame exposes an Android-app OpenXR runtime at all (the OTHER
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big external unknown — the shim is moot if the APK can't load there).
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