feat: switch trigger physics volumes on and off at runtime

The ActivatePhysics trigger command was a TODO. The client activates or
deactivates the object's physics component
(LWOPhysicsSystemComponent::msgActivatePhysics, 1.10.64 0x00ccf970);
the server now does the same to phantom physics: switching it off takes
the volume out of the physics world (dpWorld::DetachEntity, without
deleting it) and makes whatever was inside leave, switching it on adds
it back and whatever is inside enters on the next step. This lets
trigger driven volumes like the monument lasers turn on and off.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

dGame/dComponents/PhantomPhysicsComponent.cpp

@@ -87,9 +87,31 @@ PhantomPhysicsComponent::PhantomPhysicsComponent(Entity* parent, const int32_t c
 	}
 }
 
+void ApplyCollisionEffect(const LWOOBJID& target, const ePhysicsEffectType effectType, const float effectScale);
+
 PhantomPhysicsComponent::~PhantomPhysicsComponent() {
-	if (m_dpEntity) {
-		dpWorld::RemoveEntity(m_dpEntity);
+	if (!m_dpEntity) return;
+
+	if (m_PhysicsActive) dpWorld::RemoveEntity(m_dpEntity);
+	else delete m_dpEntity;
+}
+
+void PhantomPhysicsComponent::SetPhysicsActive(const bool active) {
+	if (!m_dpEntity || m_PhysicsActive == active) return;
+	m_PhysicsActive = active;
+
+	if (active) {
+		// Anything already inside enters on the next physics step
+		dpWorld::AddEntity(m_dpEntity);
+		return;
+	}
+
+	dpWorld::DetachEntity(m_dpEntity);
+	const std::vector<LWOOBJID> inside(m_dpEntity->GetCurrentlyCollidingObjects().begin(), m_dpEntity->GetCurrentlyCollidingObjects().end());
+	m_dpEntity->ClearCollisions();
+	for (const auto id : inside) {
+		ApplyCollisionEffect(id, m_EffectType, 1.0f);
+		m_Parent->OnCollisionLeavePhantom(id);
 	}
 }
 
@@ -151,7 +173,7 @@ void ApplyCollisionEffect(const LWOOBJID& target, const ePhysicsEffectType effec
 }
 
 void PhantomPhysicsComponent::Update(float deltaTime) {
-	if (!m_dpEntity) return;
+	if (!m_dpEntity || !m_PhysicsActive) return;
 
 	//Process enter events
 	for (const auto id : m_dpEntity->GetNewObjects()) {

dGame/dComponents/PhantomPhysicsComponent.h

@@ -99,6 +99,14 @@ public:
 
 	dpEntity* GetdpEntity() const { return m_dpEntity; }
 
+	/**
+	 * Switches the volume on or off (the ActivatePhysics trigger command; the client activates or deactivates
+	 * the physics component the same way). Whatever was inside leaves when it is switched off.
+	 */
+	void SetPhysicsActive(bool active);
+
+	bool GetPhysicsActive() const { return m_PhysicsActive; }
+
 	/**
 	 * Spawns an object at each of the vertices for debugging purposes
 	 */
@@ -161,6 +169,9 @@ private:
 	 */
 	dpEntity* m_dpEntity;
 
+	// Whether m_dpEntity is in the physics world
+	bool m_PhysicsActive = true;
+
 	/**
 	 * Whether or not this physics object represents an object that updates the respawn pos of an entity that crosses it
 	 */

dGame/dComponents/TriggerComponent.cpp

@@ -467,13 +467,18 @@ void TriggerComponent::HandleDestroySpawnerNetworkObjects(std::string args) {
 }
 
 void TriggerComponent::HandleActivatePhysics(Entity* targetEntity, std::string args) {
-	if (args == "true") {
-		// TODO add physics entity if there isn't one
-	} else if (args == "false") {
-		// TODO remove Phsyics entity if there is one
-	} else {
+	if (args != "true" && args != "false") {
 		LOG_DEBUG("Invalid argument for ActivatePhysics Trigger: %s", args.c_str());
+		return;
 	}
+
+	auto* const phantomPhysicsComponent = targetEntity->GetComponent<PhantomPhysicsComponent>();
+	if (!phantomPhysicsComponent) {
+		LOG_DEBUG("ActivatePhysics on %llu:%i which has no phantom physics", targetEntity->GetObjectID(), targetEntity->GetLOT());
+		return;
+	}
+
+	phantomPhysicsComponent->SetPhysicsActive(args == "true");
 }
 
 void TriggerComponent::HandleSetPath(Entity* targetEntity, std::vector<std::string> argArray) {

dPhysics/dpEntity.h

@@ -57,6 +57,9 @@ public:
 
 	void PreUpdate() { m_NewObjects.clear();  m_RemovedObjects.clear(); }
 
+	// Forgets everything it touches (it was taken out of the world)
+	void ClearCollisions() { m_NewObjects.clear(); m_RemovedObjects.clear(); m_CurrentlyCollidingObjects.clear(); }
+
 	const LWOOBJID& GetObjectID() const { return m_ObjectID; }
 
 	void SetGrid(dpGrid* grid);

dPhysics/dpGrid.cpp

@@ -73,6 +73,12 @@ void dpGrid::Move(dpEntity* entity, float x, float z) {
 }
 
 void dpGrid::Delete(dpEntity* entity) {
+	if (!entity) return;
+	Remove(entity);
+	delete entity;
+}
+
+void dpGrid::Remove(dpEntity* entity) {
 	if (!entity) return;
 	int oldCellX = static_cast<int>(std::round(entity->m_Position.x)) / dpGrid::CELL_SIZE + NUM_CELLS / 2;
 	int oldCellZ = static_cast<int>(std::round(entity->m_Position.z)) / dpGrid::CELL_SIZE + NUM_CELLS / 2;
@@ -88,10 +94,11 @@ void dpGrid::Delete(dpEntity* entity) {
 		cell.pop_back();
 	}
 
-	m_GargantuanObjects.erase(entity->m_ObjectID);
+	const auto gargantuan = m_GargantuanObjects.find(entity->m_ObjectID);
+	if (gargantuan != m_GargantuanObjects.end() && gargantuan->second == entity) m_GargantuanObjects.erase(gargantuan);
 
-	if (entity) delete entity;
-	entity = nullptr;
+	// Out of the grid: moving it mustn't put it back into a cell
+	entity->m_Grid = nullptr;
 }
 
 void dpGrid::Update(float deltaTime) {

dPhysics/dpGrid.h

@@ -20,6 +20,11 @@ public:
 	void Move(dpEntity* entity, float x, float z);
 	void Delete(dpEntity* entity);
 
+	/**
+	 * Takes an entity out of the grid without deleting it
+	 */
+	void Remove(dpEntity* entity);
+
 	void Update(float deltaTime);
 
 	/**

dPhysics/dpWorld.cpp

@@ -128,6 +128,20 @@ void dpWorld::AddEntity(dpEntity* entity) {
 	}
 }
 
+void dpWorld::DetachEntity(dpEntity* entity) {
+	if (!entity) return;
+
+	if (m_Grid) {
+		m_Grid->Remove(entity);
+		return;
+	}
+
+	auto& entities = entity->GetIsStatic() ? m_StaticEntities : m_DynamicEntites;
+	for (auto& other : entities) {
+		if (other == entity) other = nullptr;
+	}
+}
+
 void dpWorld::RemoveEntity(dpEntity* entity) {
 	if (!entity) return;
 

dPhysics/dpWorld.h

@@ -18,5 +18,10 @@ namespace dpWorld {
 	void AddEntity(dpEntity* entity);
 	void RemoveEntity(dpEntity* entity);
 
+	/**
+	 * Takes an entity out of the world without deleting it, so it can be added back later (a volume switched off)
+	 */
+	void DetachEntity(dpEntity* entity);
+
 	dNavMesh* GetNavMesh();
 };

tests/dGameTests/CollisionFilterTests.cpp

@@ -77,3 +77,34 @@ TEST(CollisionFilterTests, RotatedBoxesKeepTheirShape) {
 	EXPECT_NEAR(box->SquaredDistanceTo(NiPoint3(100.0f, 12.0f, 100.0f)), 4.0f, 1e-3f);
 	EXPECT_NEAR(box->SquaredDistanceTo(NiPoint3(100.0f, -3.0f, 100.0f)), 9.0f, 1e-3f);
 }
+
+#include "dpWorld.h"
+#include "dpGrid.h"
+
+TEST(CollisionFilterTests, DetachedVolumesStopColliding) {
+	dpGrid grid(8, 100);
+	auto* volume = new dpEntity(1, 5.0f);
+	auto* player = new dpEntity(2, 1.0f, false);
+	volume->SetPosition(NiPoint3Constant::ZERO);
+	player->SetPosition(NiPoint3(1.0f, 0.0f, 0.0f));
+	volume->SetGrid(&grid);
+	player->SetGrid(&grid);
+
+	grid.Update(0.1f);
+	ASSERT_EQ(volume->GetNewObjects().size(), 1u);
+
+	// Switched off: out of the grid, moving it doesn't sneak it back in, and it stops seeing anything
+	grid.Remove(volume);
+	volume->ClearCollisions();
+	volume->SetPosition(NiPoint3(0.5f, 0.0f, 0.0f));
+	grid.Update(0.1f);
+	EXPECT_TRUE(volume->GetCurrentlyCollidingObjects().empty());
+
+	// Switched back on: sees the player again
+	volume->SetGrid(&grid);
+	grid.Update(0.1f);
+	EXPECT_EQ(volume->GetNewObjects().size(), 1u);
+
+	grid.Delete(volume);
+	grid.Delete(player);
+}