feat(physics): add runtime physics scaffolding

engine/src/Scene/SceneRuntime.cpp

@@ -1,5 +1,6 @@
 #include "Scene/SceneRuntime.h"
 
+#include <XCEngine/Physics/PhysicsWorld.h>
 #include "Scripting/ScriptEngine.h"
 #include <XCEngine/UI/Runtime/UISceneRuntimeContext.h>
 
@@ -28,6 +29,7 @@ void SceneRuntime::Start(Scene* scene) {
     }
 
     m_scene = scene;
+    CreatePhysicsWorldForScene(scene);
     m_running = true;
     m_uiRuntime->Reset();
     Scripting::ScriptEngine::Get().OnRuntimeStart(scene);
@@ -35,12 +37,14 @@ void SceneRuntime::Start(Scene* scene) {
 
 void SceneRuntime::Stop() {
     if (!m_running) {
+        DestroyPhysicsWorld();
         m_uiRuntime->Reset();
         m_scene = nullptr;
         return;
     }
 
     Scripting::ScriptEngine::Get().OnRuntimeStop();
+    DestroyPhysicsWorld();
     m_uiRuntime->Reset();
     m_running = false;
     m_scene = nullptr;
@@ -48,12 +52,14 @@ void SceneRuntime::Stop() {
 
 void SceneRuntime::ReplaceScene(Scene* scene) {
     if (!m_running) {
+        DestroyPhysicsWorld();
         m_scene = scene;
         m_uiRuntime->Reset();
         return;
     }
 
     m_scene = scene;
+    CreatePhysicsWorldForScene(scene);
     m_uiRuntime->Reset();
     Scripting::ScriptEngine::Get().OnRuntimeSceneReplaced(scene);
 }
@@ -66,6 +72,9 @@ void SceneRuntime::FixedUpdate(float fixedDeltaTime) {
     // Scripts run first so their state changes are visible to native components in the same frame.
     Scripting::ScriptEngine::Get().OnFixedUpdate(fixedDeltaTime);
     m_scene->FixedUpdate(fixedDeltaTime);
+    if (m_physicsWorld) {
+        m_physicsWorld->Step(fixedDeltaTime);
+    }
 }
 
 void SceneRuntime::Update(float deltaTime) {
@@ -115,5 +124,29 @@ void SceneRuntime::ClearQueuedUIInputEvents() {
     m_uiRuntime->ClearQueuedInputEvents();
 }
 
+void SceneRuntime::CreatePhysicsWorldForScene(Scene* scene) {
+    if (!scene) {
+        DestroyPhysicsWorld();
+        return;
+    }
+
+    DestroyPhysicsWorld();
+
+    auto physicsWorld = std::make_unique<Physics::PhysicsWorld>();
+    Physics::PhysicsWorldCreateInfo createInfo = {};
+    createInfo.scene = scene;
+    physicsWorld->Initialize(createInfo);
+    m_physicsWorld = std::move(physicsWorld);
+}
+
+void SceneRuntime::DestroyPhysicsWorld() {
+    if (!m_physicsWorld) {
+        return;
+    }
+
+    m_physicsWorld->Shutdown();
+    m_physicsWorld.reset();
+}
+
 } // namespace Components
 } // namespace XCEngine