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fix #180: port retail's stateful camera sought-position - the sweep target converges onto the wall contact

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The camera-collision sweep strobed the eye 0.27m every ~5-10 frames while
the compressed chase boom moved along corridor walls (pulledIn 0.27<->0.53
on ~1.4mm input drift): RetailChaseCamera re-demanded the FULL-length ideal
boom from scratch each frame, so the pivot->eye ray re-rolled the same
knife-edge r+-eps graze on the double-faced slabs every frame, and its two
first-contact solutions tear-interleaved at ~1700fps into the #176
"stripes/triangles".

Retail never re-rolls that ray. CameraManager::UpdateCamera (0x00456660)
interpolates FROM THE CURRENT SWEPT VIEWER toward the desired pose
(interpolate_origin/rotation, stiffness 0.45 x dt x 10, clamped) and the
result becomes viewer_sought_position (SmartBox::PlayerPhysicsUpdatedCallback
0x00452d60); update_viewer (0x00453ce0) sweeps pivot->SOUGHT. Pressed against
a wall the sweep ray extends one interpolation step past the contact
(sub-mm at high fps), so a bistable graze can move the eye by at most that
step - the strobe is structurally impossible. A 0.4mm/2e-4 dead-band parks
the sought exactly on the viewer when converged (0x00456fcd-0x00457035).

- RetailChaseCamera: _dampedEye -> _soughtEye + _publishedEye (retail's two
  Positions); lerp base = the published (swept) viewer; sweep targets the
  sought; total-fallback (ViewerCellId==0) resets the sought like
  set_viewer(player_pos, 1). The old "collision must NOT feed back into the
  damped state" comment had the coupling backwards - what stays clean is the
  transient desired pose, not the sought.
- SweepEye untouched (faithful update_viewer port, exonerated by the #180
  investigation).
- Tests: the old pin asserting instant full re-extension after a clamp
  (the divergence itself) replaced with four retail pins: gradual
  re-extension, sweep-target-converges-onto-contact, total-fallback
  re-extends from the player, wall-press glide stability.
- Pseudocode doc: docs/research/2026-07-06-camera-sought-position-pseudocode.md
  (UpdateCamera tail incl. the sought derivation + set_viewer reset semantics
  + Frame interpolate/close_rotation).
- Register: AD-37 (forward-vector nlerp vs quaternion slerp), AD-38
  (init-at-full-extension vs retail re-extend-from-player) - both
  pre-existing, identified during the decomp reading.

Suites green (Core 2599+2skip / App 729+2skip / UI 425 / Net 385).
Pending: autonomous visual verify + user gate (#180 + the #176 re-gate).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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8
docs/ISSUES.md
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@ -48,7 +48,13 @@ Copy this block when adding a new issue:
## #180 — Camera-collision sweep bistable at a compressed boom → per-frame eye strobe (the #176 "stripes")
**Status:** OPEN — mechanism PINNED numerically; fix = port retail's stateful sought-position
**Status:** 🟡 FIX SHIPPED 2026-07-06 (stateful sought-position ported per
`CameraManager::UpdateCamera` 0x00456660 — the interpolation base is the
CURRENT swept viewer and the sweep targets the converging sought, never the
full-length boom; pseudocode
`docs/research/2026-07-06-camera-sought-position-pseudocode.md`; register
AD-37/AD-38 filed for the two pre-existing adaptations found in the reading).
Awaiting autonomous visual verify + the user gate (with the #176 re-gate).
**Severity:** HIGH (the visible flicker/stripe artifact the #176 gate keeps failing on; corridor camera constantly rides walls)
**Filed:** 2026-07-06
**Component:** camera / physics (NOT render — every render suspect eliminated by isolation)

2
docs/architecture/retail-divergence-register.md
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@ -96,6 +96,8 @@ accepted-divergence entries (#96, #49, #50).
| AD-34 | Retail's intrusive `DLListBase`/`DLListData` lists are managed `LinkedList<T>`s; node identity via `LinkedListNode<>` references (Phase R1 anim list, 2026-07-02; extended R2-Q3 to `MotionTableManager.pending_animations`; extended R4-V2 to `MoveToManager.pending_actions` — whose node type, retail `MoveToManager::MovementNode`, is RENAMED `MoveToNode` to avoid colliding with R2's `Motion/MotionNode.cs` pending_motions node) | `src/AcDream.Core/Physics/Motion/CSequence.cs` (`_animList`); `src/AcDream.Core/Physics/Motion/MotionTableManager.cs` (`_pendingAnimations`); `src/AcDream.Core/Physics/Motion/MoveToManager.cs` (`_pendingActions`) + `MoveToNode.cs` | Same topology + cursor semantics (curr_anim/first_cyclic/tail-anchored scans are node references); unlink/delete becomes `Remove(node)`; conformance tests pin the surgery state tables | Any retail behavior depending on the −4 pointer adjustment or node memory reuse (none observed in the decomp) would diverge; a reader grepping for retail's `MovementNode` name must find it via this row | `acclient.h` DLListBase; `r1-csequence-decomp.md` §0; `r2-motiontable-decomp.md` §11; `r4-moveto-decomp.md` node factories §4a |
| AD-35 | `MotionTableManager.PerformMovement`'s unhandled-type default case returns the named sentinel `0xFFFFFFFF` (`MotionTableManagerError.NotHandled`); retail's compiled code leaks the `CSequence*` pointer reinterpreted as the return code (BN-confirmed artifact, dead/unreachable — callers gate on type first) (R2-Q3, 2026-07-02) | `src/AcDream.Core/Physics/Motion/MotionTableManager.cs` (`PerformMovement` default case) | No retail caller consults the return value for unhandled types (RawCommand/StopRawCommand/MoveTo\*/TurnTo\* route elsewhere); returning a stable non-zero sentinel preserves the only observable contract (non-zero = not success) without fabricating a pointer-shaped number | If a future port wires a caller that passes unhandled types AND branches on the exact return value, it would see `0xFFFFFFFF` where retail saw an arbitrary pointer — flag at that port | `PerformMovement` 0x0051c0b0 (`r2-motiontable-decomp.md` §11 default-case note) |
| AD-36 | `IMotionDoneSink.MotionDone` consumed for CREATURE-class entities only: R3-W2 binds the seam to the entity's `MotionInterpreter.MotionDone` (player via `PlayerMovementController.Motion`, remotes via `RemoteMotion.Motion`, resolved at fire time); interp-less entities (statics that never receive a UM/UP and so never get a `RemoteMotion`) keep a diagnostic-recorder-only target — retail gives every CPhysicsObj a MovementManager/CMotionInterp (R2-Q4 seam, narrowed R3-W2, 2026-07-02; R5-V5 gave every `RemoteMotion`/player ONE literal `MovementManager` facade, so the residue is only the no-RemoteMotion class) | `src/AcDream.App/Rendering/GameWindow.cs` (TickAnimations MotionDoneTarget bind) | Motion for entities without a `RemoteMotion` (never UM/UP-touched) completes via the manager queue alone; nothing consumes their MotionDone until every sequencer-owning entity gets a host/`RemoteMotion` (doors DO have one since the R4-V5 door fix — first UM creates it) | An entity behavior depending on pending_motions bookkeeping in that no-RemoteMotion class (none known) would silently no-op | `CPhysicsObj::MotionDone` 0x0050fdb0; retire when every sequencer-owning entity constructs a `RemoteMotion`/host (post-M1.5 entity-class unification; R5-V5 closed the facade half) |
| AD-37 | Camera rotation state is a forward VECTOR (nlerp + normalize; roll always 0, up = world Z); retail's sought carries a full Frame and slerps quaternions (`Frame::interpolate_rotation` shortest-path slerp with 2e-4 nlerp fallback). The dead-band compares forward-vector distance against the same 2e-4 epsilon retail applies per quaternion component | `src/AcDream.App/Rendering/RetailChaseCamera.cs` (`_dampedForward`, `ApplyConvergenceSnap`) | The chase camera never rolls (heading frames are Z-up by construction), so a forward vector spans the reachable rotation space; identified (not introduced) during the #180 UpdateCamera tail reading | If a future camera mode needs roll (death cam, cutscene) the vector state can't represent it; large-angle per-frame turns nlerp (chord) vs slerp (arc) — imperceptible at 0.45-stiffness step sizes | `Frame::interpolate_rotation` 0x00535390, `Frame::close_rotation` 0x00455d70; pseudocode doc 2026-07-06-camera-sought-position |
| AD-38 | First camera frame seats sought = viewer = the full-length target eye (starts converged); retail hard resets both to the PLAYER's position (`set_viewer(pos, reset_sought=1)`) at login/teleport/cell-loss, so the retail camera visibly re-extends outward from the head over ~1 s | `src/AcDream.App/Rendering/RetailChaseCamera.cs` (`_initialised` branch) | acdream teleports don't reset the camera object today; the pivot-anchored sweep self-heals in one convergence, and the login zoom-out is cosmetic. Identified (not introduced) during the #180 reading | Login/teleport first frames show a fully-extended boom where retail shows a zoom-out; if a teleport lands the stale sought behind distant geometry the first sweeps clip until convergence (sub-second) | `SmartBox::set_viewer` 0x00452c40 (reset_sought=1 sites pc:92775, pc:92886); retire by wiring teleport → sought reset |
---

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# Retail camera sought-position derivation — pseudocode (#180 fix)
Source: `docs/research/named-retail/acclient_2013_pseudo_c.txt` (Sept 2013 EoR
build, PDB-named Binary Ninja decomp). Read 2026-07-06 for #180 (the
camera-sweep eye strobe = the #176 "stripes").
Functions covered (address = retail VA, line = pseudo-C line):
| Function | VA | pseudo-C line |
|---|---|---|
| `CameraManager::UpdateCamera` | `0x00456660` | 95505 |
| `SmartBox::PlayerPhysicsUpdatedCallback` | `0x00452d60` | 91836 |
| `SmartBox::set_viewer` | `0x00452c40` | 91780 |
| `SmartBox::update_viewer` (consumption; already ported) | `0x00453ce0` | 92761 |
| `CameraManager::QueryPivotPosition` | `0x004564f0` | 95448 |
| `Frame::interpolate_origin` | `0x005352f0` | 319607 |
| `Frame::interpolate_rotation` | `0x00535390` | 319618 |
| `Frame::close_rotation` | `0x00455d70` | 94838 |
| `CameraManager::CameraManager` (ctor defaults) | `0x00457090` | 95957 |
## 1. The state machine — three Positions, one loop
`SmartBox` holds **two viewer Positions**; `CameraManager` computes a third
(the desired pose) transiently each frame:
- **`viewer`** — the PUBLISHED camera pose. What the renderer/sound/sky use.
Written only by `set_viewer` (the swept result each frame).
- **`viewer_sought_position`** — the STATEFUL sweep target. Persisted across
frames. Converges from the current `viewer` toward the desired pose.
- **desired pose** (transient inside `UpdateCamera`) — pivot + heading-rotated
`viewer_offset`, the full-length ideal boom. Never swept directly.
Per-frame loop (order matters):
```
CPhysics::UseTime (0x00509900 loop, line 271640):
for each physics obj: CPhysicsObj::update_object(obj)
if obj == player:
SmartBox::PlayerPhysicsUpdatedCallback(smartbox) // 0x005099f2
→ sought = CameraManager::UpdateCamera(mgr, &viewer) // ← CURRENT swept viewer in
...later in the frame...
SmartBox::UseTime → SmartBox::update_viewer (called at 0x00454c34)
→ sweep viewer_sphere: pivot → sought
→ set_viewer(swept_result, reset_sought=0) // viewer = swept; sought UNTOUCHED
```
So each frame's sweep target derives from the PREVIOUS frame's collided
position. **The full-length ideal boom ray is never re-rolled per frame** —
that is the #180 fix: after a wall contact the sought sits at (or a small step
past) the contact, and re-extends toward the ideal pose gradually.
## 2. `SmartBox::set_viewer(pos, reset_sought)` — 0x00452c40
```
set_viewer(this, pos, reset_sought):
this->viewer = pos // objcell_id + frame
if reset_sought != 0:
this->viewer_sought_position = pos // HARD RESET of the sought
this->viewer_cell = null
... (viewer light, sound listener, sky position, SceneTool::SetupCamera)
```
`reset_sought=1` call sites: teleport/hard resets, the `player->cell == 0`
bail in `update_viewer` (:92775), and the total sweep-failure fallback
(:92886). This is why retail's camera re-extends outward from your head after
a portal: sought = viewer = player position, then converges back out to the
boom.
## 3. `SmartBox::PlayerPhysicsUpdatedCallback` — 0x00452d60
```
PlayerPhysicsUpdatedCallback(this):
Position ret = CameraManager::UpdateCamera(this->camera_manager, &this->viewer)
this->viewer_sought_position = ret // objcell_id (0x00452d84) + frame (0x00452d87)
```
The argument is `&this->viewer` — the **current swept** viewer, not the
previous sought. The return becomes the new sought.
## 4. `CameraManager::UpdateCamera(this, ret, viewer)` — 0x00456660
Head (previously read): disabled bail, dt bookkeeping, manual offset-key
integration, pivot query. Tail (read this session): the desired pose + the
stateful interpolation. Full shape:
```
UpdateCamera(this, ret, viewer): // viewer = SmartBox::viewer (swept)
if !m_bEnabled: return viewer // 0x00456672 — pass-through
dt = Timer::cur_time - last_update_time // real seconds, float64
last_update_time = Timer::cur_time
// Manual camera-adjust keys integrate into the offsets (held-key rates):
if m_dwCameraOffsetMovement: viewer_offset += FlagsToVector(flags) * dt // 0x004566ca
if m_dwPivotOffsetMovement: pivot_offset += FlagsToVector(flags) * dt // 0x00456718
pivot_obj = CPhysicsObj::GetObjectA(pivot_object_id)
ok = pivot_obj != null && QueryPivotPosition(&pivotPos) // 0x004567f1
if !ok: return viewer // 0x00457050 tail — pass-through
// ── Everything below happens in the VIEWER's coordinate space ──
p = Position::localtoglobal(viewer, pivotPos) // pivot origin in viewer space (0x00456815)
look = (0,0,0) // the look-direction accumulator
if target_status & 2: // LOOK_AT_OBJECT (0x0045684a)
target = GetObjectA(target_object_id) // + optional part anchor
t = localtoglobal(viewer, targetPos, target_offset)
d = t - p
if normalize(d) ok: look += d
if m_bAlignCameraToSlope && (target_status & 0x10): // ALIGN_WITH_PLANE (0x00456928)
avgVel = 5-slot ring average of pivot velocity // 0x00456944..0x00456a5f
if normalize(avgVel) ok:
if |avgVel.x| < 2e-4 && |avgVel.y| < 2e-4: // near-vertical motion only
n = (transient_state & CONTACT) ? contact_plane.N
: (heading-of-avgVel or (0,0,1)) // 0x00456ab1
fwd = pivot's local +Y in world // localtoglobalvec (0x00456b90)
slopeFwd = fwd - n * dot(fwd, n) // project facing onto the plane
if normalize(slopeFwd) ok:
if target_status & 1: look += headingFrame(slopeFwd).rotate(direction)
else: look += slopeFwd
else if target_status & 1: look += pivot.rotate(direction)
else: // not moving →
if target_status & 1: // LOOK_IN_DIRECTION (0x00456dfa)
look += pivot.rotate(direction) // player facing ⊗ this->direction
if normalize(look) failed: // 0x00456ca4 — degenerate accumulator
look = pivot.rotate(direction) // fall back to the facing direction
// ── Desired pose: boom offset in the heading frame ──
Frame headingFrame // var_40
headingFrame.origin = p // pivot, viewer-space (0x00456cd7-0x00456cf1)
headingFrame.set_vector_heading(look) // 0x00456cf8
desiredEye = headingFrame.localtoglobal(viewer_offset) // pivot + R(look)·offset (0x00456d0d)
if target_status & 4: // LOOK_AT_PIVOT (0x00456d33)
look = p - desiredEye // re-aim from the DESIRED eye at the pivot
if normalize(look) failed: look = (0,0,0)
if normalize(look) failed: // 0x00456e59
look = pivot.rotate(direction)
Frame desired // var_c8
desired.origin = desiredEye
desired.set_vector_heading(look) // 0x00456e8c
// ── Stiffness → per-frame interpolation factors ──
tSnap = t_stiffness >= 1.0 - 2e-4 // 0x00456e9e
t = tSnap ? 1.0 : min(t_stiffness * dt * 10, 1.0) // 0x00456ec2
rSnap = r_stiffness >= 1.0 - 2e-4 // 0x00456ee1
r = rSnap ? 1.0 : min(r_stiffness * dt * 10, 1.0) // 0x00456f04
// ── THE STATEFUL STEP: interpolate FROM THE SWEPT VIEWER ──
Frame f // var_150
f.interpolate_origin(viewer.frame, desired, t) // lerp origins (0x00456fae)
f.interpolate_rotation(viewer.frame, desired, r) // slerp quaternions (0x00456fc8)
// ── Dead-band: park the sought ON the viewer when converged ──
if !tSnap: // 0x00456fe6
if distance(f.origin, viewer) < 4e-4 // 2 × 2e-4 m (0x00456fe1, 0x00456fed)
&& !rSnap
&& Frame::close_rotation(f, viewer.frame, 2e-4):
return viewer // EXACT copy — sought parks on the viewer
return Position{ objcell_id: viewer.objcell_id, frame: f } // 0x00457038-0x00457071
```
Ctor defaults (0x00457090): `t_stiffness = r_stiffness = 0.45`,
`viewer_offset = (0,-3,0)`, `direction = (0,1,0)`,
`target_status = LOOK_IN_DIRECTION`, `m_bAlignCameraToSlope = 1`,
`m_rCameraAdjustmentSpeed = 40`.
### Units & feel
`t = 0.45 · dt · 10 = 4.5·dt` → an exponential approach with rate constant
4.5/s (time constant ≈ 0.22 s: the sought covers ~63% of the remaining gap
every 0.22 s, frame-rate independently). The dead-band (0.4 mm translation +
2e-4 quaternion-component rotation) turns the asymptote into an exact fixed
point.
## 5. Consumption: `SmartBox::update_viewer` — 0x00453ce0 (already ported)
Already faithfully ported by `PhysicsCameraCollisionProbe.SweepEye`
(exonerated in the #180 investigation — see the handoff's DO-NOT-RETRY). For
completeness, the sought's role:
```
update_viewer(this):
if player.cell == null: set_viewer(player.pos, reset_sought=1); return // :92775
pivot = player/part frame origin + R·pivot_offset // :92815
startCell = indoor ? AdjustPosition-seat at pivot : player.cell // :92832
sweep viewer_sphere (r=0.3): pivot → viewer_sought_position, flags 0x5c // :92860-92868
if find_valid_position ok: set_viewer(swept.curr_pos, 0); viewer_cell = swept.curr_cell
else if AdjustPosition(sought) ok: set_viewer(sought_seated, 0)
else: set_viewer(player.pos, reset_sought=1); viewer_cell = null // :92886
```
Note both `reset_sought=1` sites map to acdream's
`CameraSweepResult.ViewerCellId == 0` returns in `SweepEye` (the cell-0 bail
and Fallback 2) — a clean 1:1 seam for the port.
## 6. Frame helpers
```
Frame::interpolate_origin(this, a, b, t): // 0x005352f0
this.origin = (1-t)·a.origin + t·b.origin // plain lerp
Frame::interpolate_rotation(this, a, b, t): // 0x00535390
d = dot(a.q, b.q)
if d < 0: b.q = -b.q; d = -d // shortest-path sign flip
if 1-d < 2e-4: w = (1-t, t) // near-identical → nlerp weights
else: θ = acos(d); w = (sin((1-t)θ), sin(tθ)) / sin θ // slerp
this.q = w₀·a.q + w₁·b.q // (+ re-cache)
Frame::close_rotation(a, b, eps): // 0x00455d70
return |a.qw-b.qw| ≤ eps && |a.qx-b.qx| ≤ eps
&& |a.qy-b.qy| ≤ eps && |a.qz-b.qz| ≤ eps // component-wise, all four
```
## 7. Why this kills the #180 strobe (mechanism)
The probed failure: with the compressed boom moving along a wall, the
full-length pivot→ideal-eye ray grazes the corridor's double-faced slabs at
r±ε and has TWO first-contact solutions 0.27 m apart; mm-scale input drift
flips between them every few frames (`pulledIn` 0.27 ↔ 0.53).
With the retail sought: the target sits a single interpolation step past the
current contact — `α·|desired−viewer|` ≈ 0.7 mm at 1700 fps, ≈ 2 cm at 60 fps
(for the 0.27 m compression). The sweep ray extends only that far past the
wall, so even a bistable contact solution can only move the eye by the step
size, not 0.27 m. The strobe amplitude collapses from 0.27 m to sub-mm; the
eye glides along the wall following the player's drift. No damping of the
SWEPT result is involved — the published eye still hard-follows the sweep
every frame, exactly like retail.
## 8. Port mapping → `RetailChaseCamera`
| Retail | acdream |
|---|---|
| `viewer` (swept, published) | `_publishedEye` (+ `Position` property) |
| `viewer_sought_position` | `_soughtEye` (was `_dampedEye` — which wrongly lerped from ITSELF) |
| desired pose (transient) | `targetEye`/`targetForward` (existing boom math — unchanged) |
| `interpolate_origin(viewer→desired, t)` | `Vector3.Lerp(_publishedEye, targetEye, tAlpha)` |
| `interpolate_rotation(viewer→desired, r)` | forward-vector lerp (adaptation — register AD-37) |
| dead-band `return viewer` | `ApplyConvergenceSnap(_publishedEye, …)` parks sought on the viewer |
| `set_viewer(pos, 1)` resets sought | `swept.ViewerCellId == 0` → `_soughtEye = swept.Eye` |
| sweep pivot→sought | `SweepEye(pivotWorld, _soughtEye, …)` (was `_dampedEye` = full boom) |
Intentional adaptations (register rows added with the port commit):
- **AD-37** — rotation state is a forward VECTOR (nlerp + normalize, roll
always 0, up = world Z) instead of retail's quaternion slerp
(`interpolate_rotation` 0x00535390). Pre-existing shape of
`RetailChaseCamera`; the close_rotation dead-band test compares forward
vectors against the same 2e-4 epsilon.
- **AD-38** — first-frame init seats sought = viewer = the full-length target
eye; retail initializes via `set_viewer(player_pos, 1)` so the camera
re-extends from the player's head at login/teleport. acdream's teleports
don't reset the camera today; the pivot-anchored sweep self-heals within
one convergence (~1 s).
The previous in-code comment ("the collision must NOT feed back into the
damped state — retail keeps viewer_sought_position separate from viewer")
was WRONG about the direction of the coupling: retail's sought is derived
FROM the swept viewer every frame (0x00452d75); what stays clean is the
*desired pose*, which is recomputed transiently and never swept directly.
The old shape (lerp sought→ideal from itself + sweep the full boom) is what
made the knife-edge re-roll — and the #180 strobe — possible.