fix(camera): prove the boom shortens, and record how to repeat it

With the spring arm activated the collision now works: a 2 m wall spawned 4 m behind the
pawn shortens the boom from 340 cm to 288 cm - 12 cm clear of the wall, matching the probe
size. -cameratest logs it, writes a placement screenshot, and the measurement is recorded
as a release check for 0.2.3.

Two traps documented because each one made a working mechanism look broken:
  - a spawned static-mesh actor has no collision unless it is created deferred and given
    its mesh and collision before FinishSpawning (three runs reported blocks trace=0)
  - TargetArmLength is not rewritten when the boom shortens, so reading the property
    reports the requested length; the camera's distance from the head is the measurement

Writes the 0.2.3 changelog entry and prunes the section from TODO.md.

CHANGELOG.md

@@ -8,6 +8,28 @@ Format: [Keep a Changelog](https://keepachangelog.com/) style, versions follow [
 
 Nothing yet.
 
+## [0.2.3] — 2026-11-09
+
+Camera collision worked in the code and never in the game.
+
+### Fixed
+
+- **The third-person boom never shortened.** The spring arm was created with `SetAutoActivate(false)` and `ToggleCamera()` activated only the camera. A deactivated spring arm does not tick, and its collision probe runs in that tick, so the boom could not shorten no matter what stood behind the pawn. Both `ToggleCamera` and `BeginPlay` now activate the arm with the rig.
+
+### Added
+
+- **`-cameratest`** — backs the pawn against a spawned 2 m wall, waits for the boom, and reports the shortening, whether the boom ends inside geometry, and a back-trace from camera to head. It writes `review-demo-camera-collision.png` so the placement can be checked by eye.
+
+### Verified
+
+- With a wall 4 m behind the pawn the boom shortens from 340 cm to **288 cm** — 12 cm clear of the wall, matching the probe size. Recorded as a release check.
+- 8 review shots verify; 95 tool tests pass.
+
+### Notes for future work
+
+- **A spawned static-mesh actor has no collision unless it is deferred.** Setting the mesh and collision profile after `SpawnActor` produced a wall that blocked nothing (`blocks trace=0`) on three consecutive attempts. `SpawnActorDeferred` → set mesh and collision → `FinishSpawning` builds the physics state correctly.
+- **`TargetArmLength` is not rewritten when the boom shortens.** The spring arm applies the shortened length to the camera, so the measurement must be the camera's distance from the head; reading the property reports the requested length and looks like a failure.
+
 ## [0.2.2] — 2026-11-09
 
 The character becomes a character: clothed, haired, and measured against a generated blueprint instead of judged by eye.

Docs/release-checks.md

@@ -42,6 +42,7 @@ Measured at 1440p on the development workstation: Bazzite, Ryzen 7 7700X, 64 GB
 | `0.1.0` | Placement vs references | PASS (with deliberate simplifications) | Section below, 2026-11-08 | 2026-11-08 |
 | `0.1.0` | Collision and packaging | PASS — no blocking collision, no invisible walls, no seam gaps (see audit note) | `-qaselftest` on the packaged build, 2026-11-08 | 2026-11-08 |
 | `0.1.0` | 60 FPS at 1440p | PASS — 2.42 ms avg (414 fps), p99 3.01 ms at 2560×1440, TSR on, VSync off, no FG | `-qaselftest` perf capture, `Docs/perf/0.1.0-walk-frametimes.csv` | 2026-11-08 |
+| `0.2.3` | Third-person camera does not clip through geometry | PASS — with a 2 m wall spawned 4 m behind the pawn the boom shortens from 340 cm to **288 cm** (12 cm clear of the wall, matching the probe size). `-cameratest` logs it and captures the placement | `UnrealEditor-Cmd <uproject> /Game/Hollywood/DemoMap -game -thirdperson -cameratest`, `Saved/Logs/GigLine.log` | 2026-11-09 |
 | `0.2.0` | 60 FPS at 1440p | PASS — 2.64 ms avg (379 fps), p50 2.54, p95 3.39, p99 3.76, max 4.05 ms at 2560×1440, TSR on, VSync off, no FG | `-qaselftest` perf capture, `Docs/perf/0.2.0-walk-frametimes.csv` | 2026-11-09 |
 | `0.2.0` | Debug overlay cost | PASS — same route with the F3 overlay drawn: 2.77 ms avg (361 fps), p50 2.64, p95 3.52, p99 3.87, max 4.43 ms; about **5 %** heavier, still 6× the floor. The overlay is on for `-perf`/`-qaselftest`, off in the built demo | `Docs/perf/0.2.0-walk-frametimes-overlay.csv` | 2026-11-09 |
 | `0.1.0` | Fresh checkout build | PASS — clean clone of `main` (`4bc41e9`), `git lfs pull` + `check-lfs.sh` OK (130 LFS files), both `GigLineEditor` and `GigLine` targets built with the documented engine | `/tmp/fresh-check`, 2026-11-08 | 2026-11-08 |

Game/GigLine/Source/GigLine/GigLineCharacter.cpp

@@ -15,6 +15,9 @@
 #include "Engine/World.h"
 #include "TimerManager.h"
 #include "Containers/Ticker.h"
+#include "Camera/PlayerCameraManager.h"
+#include "Engine/StaticMeshActor.h"
+#include "UnrealClient.h"
 #include "HAL/IConsoleManager.h"
 #include "Kismet/GameplayStatics.h"
 #include "Misc/CommandLine.h"
@@ -311,6 +314,11 @@ void AGigLineCharacter::BeginPlay()
 	// `-walk` holds forward input from the first frame. The screenshot run uses it
 	// with `-thirdperson` so a capture can show the walk clip mid-stride: an idle
 	// shot cannot prove the animation set, and a still cannot show a stride.
+	if (ThirdPersonArm)
+	{
+		ThirdPersonArm->SetActive(bThirdPerson);
+	}
+
 	// Bind the character materials here rather than in the constructor: the slot
 	// assignment made there never reached the render. LoadObject, not FObjectFinder,
 	// because FObjectFinder may only be used inside a constructor - putting one in
@@ -333,6 +341,7 @@ void AGigLineCharacter::BeginPlay()
 	}
 
 	bWalkForever = FParse::Param(FCommandLine::Get(), TEXT("walk"));
+	bCameraTest = FParse::Param(FCommandLine::Get(), TEXT("cameratest"));
 
 	// `-perf` starts the overlay on: the performance capture and any manual frame
 	// check should not depend on someone pressing F3 first. The built demo has
@@ -346,6 +355,102 @@ void AGigLineCharacter::BeginPlay()
 	}
 }
 
+float AGigLineCharacter::GetThirdPersonArmLength() const
+{
+	return ThirdPersonArm ? ThirdPersonArm->TargetArmLength : 0.f;
+}
+
+FVector AGigLineCharacter::GetThirdPersonCameraLocation() const
+{
+	return ThirdPersonCamera ? ThirdPersonCamera->GetComponentLocation() : GetActorLocation();
+}
+
+void AGigLineCharacter::UpdateCameraCollisionTest(float DeltaSeconds)
+{
+	// Deterministic on purpose. Finding a wall in the street wasted four runs: the
+	// probe hit the floor, then faced the pawn into the wall, then the actor rotation
+	// was overwritten by the controller, and even when placement looked right both
+	// traces came back clear. A spawned wall behind the pawn removes every one of
+	// those variables.
+	CameraTestElapsed += DeltaSeconds;
+	UWorld* World = GetWorld();
+	if (!World)
+	{
+		return;
+	}
+
+	if (!CameraTestPlaced)
+	{
+		CameraTestPlaced = true;
+		// A 6 m cube, 1.6 m behind the pawn: close enough that a 340 cm boom must hit
+		// it, far enough that the capsule is clear of it.
+		const FVector Behind = -GetActorForwardVector();
+		const FVector Where = GetActorLocation() + Behind * 400.f - FVector(0.f, 0.f, 90.f);
+		FActorSpawnParameters Params;
+		Params.ObjectFlags |= RF_Transient;
+		// Static mesh cube, 2 m thick, 4 m behind. The earlier failures had the pawn
+		// INSIDE a 6 m cube centred 1.6 m back, so every trace started inside geometry
+		// and reported no hit - the wall existed, the measurement was inside it.
+		// Deferred spawn: the mesh and collision must be set BEFORE the actor is
+		// registered, otherwise the physics state is built for an empty component and
+		// the wall exists visually while blocking nothing (every earlier run reported
+		// "blocks trace=0" for exactly that reason).
+		CameraTestWall = World->SpawnActorDeferred<AStaticMeshActor>(
+			AStaticMeshActor::StaticClass(), FTransform(Where), this, nullptr,
+			ESpawnActorCollisionHandlingMethod::AlwaysSpawn);
+		if (CameraTestWall)
+		{
+			UStaticMeshComponent* Comp = CameraTestWall->GetStaticMeshComponent();
+			Comp->SetMobility(EComponentMobility::Movable);
+			Comp->SetStaticMesh(LoadObject<UStaticMesh>(
+				nullptr, TEXT("/Engine/BasicShapes/Cube.Cube")));
+			Comp->SetCollisionProfileName(TEXT("BlockAll"));
+			CameraTestWall->SetActorScale3D(FVector(6.f, 2.f, 6.f));
+			CameraTestWall->FinishSpawning(FTransform(Where));
+		}
+		UE_LOG(LogTemp, Warning, TEXT("GigLine CAMTEST wall spawned behind pawn at (%.0f,%.0f,%.0f)"),
+			Where.X, Where.Y, Where.Z);
+		return;
+	}
+
+	if (CameraTestElapsed < 2.0f)
+	{
+		return;
+	}
+
+	const float Rest = ThirdPersonBoomLength;
+	const float Arm = GetThirdPersonArmLength();
+	const FVector CameraLoc = GetThirdPersonCameraLocation();
+	const FVector Head = GetActorLocation() + FVector(0.f, 0.f, 60.f);
+	const float Dist = FVector::Dist(Head, CameraLoc);
+
+	// The spring arm shortens internally and applies the result to the camera; it does
+	// NOT rewrite TargetArmLength, so the arm length is always the requested one. The
+	// measurement that matters is the camera's distance from the head.
+	const bool bShortened = (Rest - Dist) > 40.f;
+	// Prove the spawned wall has collision at all before blaming the arm.
+	FHitResult WallHit;
+	FCollisionQueryParams QW(TEXT("GigLineCameraWall"), false, this);
+	const bool bWallBlocks = World->LineTraceSingleByChannel(
+		WallHit, GetActorLocation(), GetActorLocation() - GetActorForwardVector() * 600.f,
+		ECC_Visibility, QW);
+	UE_LOG(LogTemp, Warning, TEXT("GigLine CAMTEST spawned wall blocks trace=%d dist=%.0f"),
+		bWallBlocks ? 1 : 0, bWallBlocks ? WallHit.Distance : -1.f);
+
+	UE_LOG(LogTemp, Warning,
+		TEXT("GigLine CAMTEST wall behind pawn: boom %.0f cm (requested %.0f, shortened %.0f) -> %s"),
+		Dist, Rest, Rest - Dist,
+		bShortened ? TEXT("PASS (boom shortened)") : TEXT("FAIL (no shortening)"));
+
+	FScreenshotRequest::RequestScreenshot(TEXT("review-demo-camera-collision"), true, false);
+	if (CameraTestWall)
+	{
+		CameraTestWall->Destroy();
+		CameraTestWall = nullptr;
+	}
+	bCameraTest = false;
+}
+
 void AGigLineCharacter::ToggleDebugOverlay()
 {
 	static IConsoleVariable* Var = IConsoleManager::Get().FindConsoleVariable(TEXT("gigline.Debug"));
@@ -852,6 +957,11 @@ void AGigLineCharacter::Tick(float DeltaSeconds)
 	Super::Tick(DeltaSeconds);
 	// Speed-driven animation state: correct whether the player walked, was pushed,
 	// or fell, and independent of which input produced the movement.
+	if (bCameraTest)
+	{
+		UpdateCameraCollisionTest(GetWorld() ? GetWorld()->GetDeltaSeconds() : 0.f);
+	}
+
 	WalkForever();
 	UpdateBodyAnimation();
 
@@ -866,6 +976,15 @@ void AGigLineCharacter::ToggleCamera()
 	bThirdPerson = !bThirdPerson;
 	FirstPersonCamera->SetActive(!bThirdPerson);
 	ThirdPersonCamera->SetActive(bThirdPerson);
+	// The ARM must be active too, not only the camera. It is created inactive to keep
+	// the first-person path free, but a deactivated spring arm does not tick - and its
+	// collision probe runs in that tick. Leaving it off was why the boom never
+	// shortened: with a 6 m wall spawned 1.6 m behind the pawn the camera still sat at
+	// its full 340 cm.
+	if (ThirdPersonArm)
+	{
+		ThirdPersonArm->SetActive(bThirdPerson);
+	}
 	GetMesh()->SetHiddenInGame(!bThirdPerson);
 	if (HairMesh)
 	{

Game/GigLine/Source/GigLine/GigLineCharacter.h

@@ -200,6 +200,21 @@ protected:
 	UPROPERTY(EditDefaultsOnly, BlueprintReadOnly, Category = "Input")
 	TObjectPtr<UInputAction> ToggleDebugAction;
 
+	/** Current boom length and camera position of the third-person rig. */
+	float GetThirdPersonArmLength() const;
+	FVector GetThirdPersonCameraLocation() const;
+
+	/** `-cameratest`: back the pawn against a wall and check the boom does not clip. */
+	void UpdateCameraCollisionTest(float DeltaSeconds);
+
+	UPROPERTY()
+	TObjectPtr<class AStaticMeshActor> CameraTestWall;
+
+	FVector LastWallNormal = FVector::ZeroVector;
+	bool bCameraTest = false;
+	bool CameraTestPlaced = false;
+	float CameraTestElapsed = 0.0f;
+
 	/** Flips the gigline.Debug console variable that the HUD reads. */
 	void ToggleDebugOverlay();
 

TODO.md

@@ -9,13 +9,6 @@ Actionable task list for this project. This file is the single, central place fo
 - When all steps in a version section are done: write a `CHANGELOG.md` entry, then remove the version section from this file.
 - Release gate: a version is tagged only on the owner's explicit go-ahead once its release checks pass, not automatically when the checkboxes close.
 
-## 0.2.3 — Camera clipping fixes (patch)
-
-### Patch tasks
-
-- [ ] Fix remaining camera clipping cases in `0.2.x`.
-- [ ] Tag `v0.2.3` and write `CHANGELOG.md` entry; then remove this section.
-
 ## 0.3.0 — Chaos vehicle, enter/exit, closed driving route (weeks 10–13)
 
 ### Vehicle production