add basic ah physicsworld

destrum/CMakeLists.txt

@@ -10,6 +10,9 @@ set(SRC_FILES
         "src/Components/Spinner.cpp"
         "src/Components/OrbitAndSpin.cpp"
 
+        "src/Components/Physics/Rigidbody.cpp"
+        "src/Components/Physics/BoxCollider.cpp"
+
         "src/Graphics/BindlessSetManager.cpp"
         "src/Graphics/Camera.cpp"
         "src/Graphics/ComputePipeline.cpp"
@@ -45,11 +48,15 @@ set(SRC_FILES
         "src/Scene/Scene.cpp"
         "src/Scene/SceneManager.cpp"
 
-
         "src/FS/AssetFS.cpp"
         "src/FS/Manifest.cpp"
 
         "src/Util/DeltaTime.cpp"
+
+        "src/Physics/PhysicsWorld.cpp"
+        "src/Physics/SimplePhysicsWorld.cpp"
+        "src/Physics/PhysicsSceneBridge.cpp"
+        src/Components/Physics/BoxCollider.cpp
 )
 
 add_library(destrum ${SRC_FILES})

destrum/include/destrum/App.h

@@ -34,6 +34,7 @@ public:
     virtual void customUpdate(float dt) = 0;
     virtual void customDraw() = 0;
     virtual void customCleanup() = 0;
+    virtual void customFixedUpdate(float dt) = 0;
 
     virtual void onWindowResize(int newWidth, int newHeight) {};
 

destrum/include/destrum/Components/Physics/BoxCollider.h

@@ -0,0 +1,31 @@
+#ifndef BOXCOLLIDER_H
+#define BOXCOLLIDER_H
+
+#include <destrum/Components/Physics/Collider.h>
+
+class BoxCollider final : public Collider {
+public:
+    explicit BoxCollider(GameObject& owner, const glm::vec3& halfExtents = glm::vec3{0.5f})
+        : Collider(owner)
+        , m_HalfExtents(halfExtents) {}
+
+    void Update() override {}
+
+
+    [[nodiscard]] PhysicsShapeDesc BuildPhysicsShape() const override {
+        return PhysicsShapeDesc::Box(m_HalfExtents, m_CenterOffset, m_IsTrigger);
+    }
+
+    [[nodiscard]] const glm::vec3& GetHalfExtents() const {
+        return m_HalfExtents;
+    }
+
+    void SetHalfExtents(const glm::vec3& halfExtents) {
+        m_HalfExtents = halfExtents;
+    }
+
+private:
+    glm::vec3 m_HalfExtents{0.5f};
+};
+
+#endif

destrum/include/destrum/Components/Physics/CapsuleCollider.h

@@ -0,0 +1,37 @@
+#pragma once
+
+#include <algorithm>
+
+#include <destrum/Components/Collider.h>
+
+class CapsuleCollider final : public Collider {
+public:
+    explicit CapsuleCollider(GameObject& owner, float radius = 0.5f, float height = 2.0f)
+        : Collider(owner)
+        , m_Radius(radius)
+        , m_Height(height) {}
+
+    [[nodiscard]] PhysicsShapeDesc BuildPhysicsShape() const override {
+        return PhysicsShapeDesc::Capsule(m_Radius, m_Height, m_CenterOffset, m_IsTrigger);
+    }
+
+    [[nodiscard]] float GetRadius() const {
+        return m_Radius;
+    }
+
+    void SetRadius(float radius) {
+        m_Radius = std::max(radius, 0.0f);
+    }
+
+    [[nodiscard]] float GetHeight() const {
+        return m_Height;
+    }
+
+    void SetHeight(float height) {
+        m_Height = std::max(height, m_Radius * 2.0f);
+    }
+
+private:
+    float m_Radius{0.5f};
+    float m_Height{2.0f};
+};

destrum/include/destrum/Components/Physics/Collider.h

@@ -0,0 +1,26 @@
+#pragma once
+
+#include <glm/glm.hpp>
+
+#include <destrum/ObjectModel/Component.h>
+#include <destrum/Physics/PhysicsTypes.h>
+
+class Collider : public Component {
+public:
+    explicit Collider(GameObject& owner)
+        : Component(owner) {}
+
+    ~Collider() override = default;
+
+    [[nodiscard]] virtual PhysicsShapeDesc BuildPhysicsShape() const = 0;
+
+    [[nodiscard]] bool IsTrigger() const { return m_IsTrigger; }
+    void SetTrigger(bool trigger) { m_IsTrigger = trigger; }
+
+    [[nodiscard]] const glm::vec3& GetCenterOffset() const { return m_CenterOffset; }
+    void SetCenterOffset(const glm::vec3& offset) { m_CenterOffset = offset; }
+
+protected:
+    bool m_IsTrigger{false};
+    glm::vec3 m_CenterOffset{0.0f};
+};

destrum/include/destrum/Components/Physics/Rigidbody.h

@@ -0,0 +1,63 @@
+#pragma once
+
+#include <glm/glm.hpp>
+
+#include <destrum/ObjectModel/Component.h>
+#include <destrum/Physics/PhysicsTypes.h>
+
+class PhysicsWorld;
+
+class Rigidbody final : public Component {
+public:
+    explicit Rigidbody(GameObject& owner)
+        : Component(owner) {}
+
+    ~Rigidbody() override = default;
+
+    void Update() override {}
+
+    void AttachPhysicsBody(PhysicsWorld* world, PhysicsBodyHandle body);
+    void DetachPhysicsBody();
+
+    [[nodiscard]] PhysicsBodyHandle GetBody() const { return m_Body; }
+    [[nodiscard]] bool HasPhysicsBody() const { return m_Body.IsValid() && m_World != nullptr; }
+
+    void AddForce(const glm::vec3& force);
+    void AddImpulse(const glm::vec3& impulse);
+
+    void SetLinearVelocity(const glm::vec3& velocity);
+    [[nodiscard]] glm::vec3 GetLinearVelocity() const;
+
+    [[nodiscard]] RigidbodyType GetType() const { return m_Type; }
+    void SetType(RigidbodyType type) { m_Type = type; }
+
+    [[nodiscard]] float GetMass() const { return m_Mass; }
+    void SetMass(float mass) { m_Mass = mass > 0.0f ? mass : 0.0001f; }
+
+    [[nodiscard]] float GetFriction() const { return m_Friction; }
+    void SetFriction(float friction) { m_Friction = friction; }
+
+    [[nodiscard]] float GetRestitution() const { return m_Restitution; }
+    void SetRestitution(float restitution) { m_Restitution = restitution; }
+
+    [[nodiscard]] bool UsesGravity() const { return m_UseGravity; }
+    void SetUseGravity(bool useGravity) { m_UseGravity = useGravity; }
+
+    [[nodiscard]] bool AllowsSleep() const { return m_AllowSleep; }
+    void SetAllowSleep(bool allowSleep) { m_AllowSleep = allowSleep; }
+
+    [[nodiscard]] PhysicsWorld* GetPhysicsWorld() const { return m_World; }
+
+private:
+    PhysicsWorld* m_World{nullptr};
+    PhysicsBodyHandle m_Body{};
+
+    RigidbodyType m_Type{RigidbodyType::Dynamic};
+
+    float m_Mass{1.0f};
+    float m_Friction{0.5f};
+    float m_Restitution{0.0f};
+
+    bool m_UseGravity{true};
+    bool m_AllowSleep{true};
+};

destrum/include/destrum/Components/Physics/SphereCollider.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <algorithm>
+
+#include <destrum/Components/Collider.h>
+
+class SphereCollider final : public Collider {
+public:
+    explicit SphereCollider(GameObject& owner, float radius = 0.5f)
+        : Collider(owner)
+        , m_Radius(radius) {}
+
+    [[nodiscard]] PhysicsShapeDesc BuildPhysicsShape() const override {
+        return PhysicsShapeDesc::Sphere(m_Radius, m_CenterOffset, m_IsTrigger);
+    }
+
+    [[nodiscard]] float GetRadius() const {
+        return m_Radius;
+    }
+
+    void SetRadius(float radius) {
+        m_Radius = std::max(radius, 0.0f);
+    }
+
+private:
+    float m_Radius{0.5f};
+};

destrum/include/destrum/ObjectModel/GameObject.h

@@ -47,13 +47,14 @@ public:
     GameObject& operator=(const GameObject& other) = delete;
     GameObject& operator=(GameObject&& other) = delete;
 
-    template <typename Component, typename... Args>
-        requires std::constructible_from<Component, GameObject&, Args...>
-    Component *AddComponent(Args&&... args) {
+    template <typename TComponent, typename... Args>
+    requires std::derived_from<TComponent, Component> &&
+             std::constructible_from<TComponent, GameObject&, Args&&...>
+    TComponent* AddComponent(Args&&... args) {
         auto& addedComponent = m_Components.emplace_back(
-            std::make_unique<Component>(*this, std::forward<Args>(args)...));
+            std::make_unique<TComponent>(*this, std::forward<Args>(args)...));
 
-        return reinterpret_cast<Component*>(addedComponent.get());
+        return static_cast<TComponent*>(addedComponent.get());
     }
 
     template <typename Component>

destrum/include/destrum/Physics/PhysicsSceneBridge.h

@@ -0,0 +1,34 @@
+#pragma once
+
+#include <memory>
+#include <vector>
+
+#include <destrum/Physics/PhysicsWorld.h>
+#include <destrum/Physics/SimplePhysicsWorld.h>
+
+class GameObject;
+
+// Small helper you can store inside Scene.
+//
+// Example:
+// class Scene {
+// public:
+//     PhysicsSceneBridge& GetPhysics() { return m_Physics; }
+// private:
+//     PhysicsSceneBridge m_Physics{std::make_unique<SimplePhysicsWorld>()};
+// };
+class PhysicsSceneBridge final {
+public:
+    explicit PhysicsSceneBridge(std::unique_ptr<PhysicsWorld> world);
+
+    [[nodiscard]] PhysicsWorld& GetWorld() { return *m_World; }
+    [[nodiscard]] const PhysicsWorld& GetWorld() const { return *m_World; }
+
+    void RegisterGameObject(GameObject& object);
+    void UnregisterGameObject(GameObject& object);
+
+    void FixedUpdate(float fixedDt);
+
+private:
+    std::unique_ptr<PhysicsWorld> m_World;
+};

destrum/include/destrum/Physics/PhysicsTypes.h

@@ -0,0 +1,118 @@
+#pragma once
+
+#include <cstdint>
+#include <limits>
+#include <glm/glm.hpp>
+#include <glm/gtc/quaternion.hpp>
+
+class GameObject;
+
+enum class RigidbodyType {
+    Static,
+    Dynamic,
+    Kinematic
+};
+
+enum class PhysicsShapeType {
+    None,
+    Box,
+    Sphere,
+    Capsule
+};
+
+struct PhysicsBodyHandle {
+    std::uint32_t id{std::numeric_limits<std::uint32_t>::max()};
+
+    [[nodiscard]] bool IsValid() const {
+        return id != std::numeric_limits<std::uint32_t>::max();
+    }
+
+    void Reset() {
+        id = std::numeric_limits<std::uint32_t>::max();
+    }
+
+    friend bool operator==(const PhysicsBodyHandle& a, const PhysicsBodyHandle& b) {
+        return a.id == b.id;
+    }
+
+    friend bool operator!=(const PhysicsBodyHandle& a, const PhysicsBodyHandle& b) {
+        return !(a == b);
+    }
+};
+
+struct PhysicsTransform {
+    glm::vec3 position{0.0f};
+    glm::quat rotation{1.0f, 0.0f, 0.0f, 0.0f};
+};
+
+struct PhysicsMaterialDesc {
+    float friction{0.5f};
+    float restitution{0.0f};
+};
+
+struct PhysicsShapeDesc {
+    PhysicsShapeType type{PhysicsShapeType::None};
+
+    // Box
+    glm::vec3 halfExtents{0.5f};
+
+    // Sphere / capsule
+    float radius{0.5f};
+
+    // Capsule full height, including the two hemispheres.
+    float height{2.0f};
+
+    // Local offset from the rigidbody transform.
+    glm::vec3 centerOffset{0.0f};
+
+    bool isTrigger{false};
+
+    [[nodiscard]] static PhysicsShapeDesc Box(const glm::vec3& halfExtents,
+                                              const glm::vec3& centerOffset = glm::vec3{0.0f},
+                                              bool isTrigger = false) {
+        PhysicsShapeDesc desc{};
+        desc.type = PhysicsShapeType::Box;
+        desc.halfExtents = halfExtents;
+        desc.centerOffset = centerOffset;
+        desc.isTrigger = isTrigger;
+        return desc;
+    }
+
+    [[nodiscard]] static PhysicsShapeDesc Sphere(float radius,
+                                                 const glm::vec3& centerOffset = glm::vec3{0.0f},
+                                                 bool isTrigger = false) {
+        PhysicsShapeDesc desc{};
+        desc.type = PhysicsShapeType::Sphere;
+        desc.radius = radius;
+        desc.centerOffset = centerOffset;
+        desc.isTrigger = isTrigger;
+        return desc;
+    }
+
+    [[nodiscard]] static PhysicsShapeDesc Capsule(float radius,
+                                                  float height,
+                                                  const glm::vec3& centerOffset = glm::vec3{0.0f},
+                                                  bool isTrigger = false) {
+        PhysicsShapeDesc desc{};
+        desc.type = PhysicsShapeType::Capsule;
+        desc.radius = radius;
+        desc.height = height;
+        desc.centerOffset = centerOffset;
+        desc.isTrigger = isTrigger;
+        return desc;
+    }
+};
+
+struct PhysicsBodyDesc {
+    GameObject* owner{nullptr};
+
+    PhysicsTransform transform{};
+    PhysicsShapeDesc shape{};
+    PhysicsMaterialDesc material{};
+
+    RigidbodyType type{RigidbodyType::Dynamic};
+
+    float mass{1.0f};
+    bool useGravity{true};
+    bool allowSleep{true};
+};

destrum/include/destrum/Physics/PhysicsWorld.h

@@ -0,0 +1,47 @@
+#pragma once
+
+#include <glm/glm.hpp>
+#include <destrum/Physics/PhysicsTypes.h>
+#include <destrum/Components/Physics/Rigidbody.h>
+
+class GameObject;
+
+struct PhysicsRaycastHit {
+    GameObject* object{nullptr};
+    PhysicsBodyHandle body{};
+    glm::vec3 point{0.0f};
+    glm::vec3 normal{0.0f, 1.0f, 0.0f};
+    float distance{0.0f};
+};
+
+class PhysicsWorld {
+public:
+    virtual ~PhysicsWorld() = default;
+
+    void RegisterRigidbody(Rigidbody& rigidbody);
+    void UnregisterRigidbody(Rigidbody& rigidbody);
+
+    virtual void Step(float fixedDt) = 0;
+
+    // - Kinematic: Transform -> physics body before Step()
+    // - Dynamic: physics body -> Transform after Step()
+    void SyncKinematicBodiesToPhysics();
+    void SyncDynamicBodiesToTransforms();
+
+    virtual PhysicsBodyHandle CreateBody(const PhysicsBodyDesc& desc) = 0;
+    virtual void DestroyBody(PhysicsBodyHandle body) = 0;
+
+    virtual void SetBodyTransform(PhysicsBodyHandle body, const PhysicsTransform& transform) = 0;
+    virtual PhysicsTransform GetBodyTransform(PhysicsBodyHandle body) const = 0;
+
+    virtual void SetLinearVelocity(PhysicsBodyHandle body, const glm::vec3& velocity) = 0;
+    virtual glm::vec3 GetLinearVelocity(PhysicsBodyHandle body) const = 0;
+
+    virtual void AddForce(PhysicsBodyHandle body, const glm::vec3& force) = 0;
+    virtual void AddImpulse(PhysicsBodyHandle body, const glm::vec3& impulse) = 0;
+
+    virtual bool Raycast(const glm::vec3& origin,
+                         const glm::vec3& direction,
+                         float maxDistance,
+                         PhysicsRaycastHit& hit) const = 0;
+};

destrum/include/destrum/Physics/SimplePhysicsWorld.h

@@ -0,0 +1,88 @@
+#pragma once
+
+#include <vector>
+#include <optional>
+
+#include <destrum/Physics/PhysicsWorld.h>
+
+class Rigidbody;
+
+// Simple CPU placeholder backend.
+//
+// This is NOT a replacement for Jolt/PhysX/Bullet.
+// It exists so your component/scene/render sync can be implemented and tested
+// before the real backend is added.
+//
+// It supports:
+// - static, dynamic, kinematic bodies
+// - gravity
+// - force/impulse integration
+// - very simple sphere/box/capsule raycasts using bounding spheres
+//
+// It does NOT support:
+// - collision response
+// - contacts
+// - friction
+// - constraints
+// - real character controllers
+class SimplePhysicsWorld final : public PhysicsWorld {
+public:
+    explicit SimplePhysicsWorld(const glm::vec3& gravity = glm::vec3{0.0f, -9.81f, 0.0f});
+
+    void Step(float fixedDt) override;
+
+    PhysicsBodyHandle CreateBody(const PhysicsBodyDesc& desc) override;
+    void DestroyBody(PhysicsBodyHandle body) override;
+
+    void SetBodyTransform(PhysicsBodyHandle body, const PhysicsTransform& transform) override;
+    PhysicsTransform GetBodyTransform(PhysicsBodyHandle body) const override;
+
+    void SetLinearVelocity(PhysicsBodyHandle body, const glm::vec3& velocity) override;
+    glm::vec3 GetLinearVelocity(PhysicsBodyHandle body) const override;
+
+    void AddForce(PhysicsBodyHandle body, const glm::vec3& force) override;
+    void AddImpulse(PhysicsBodyHandle body, const glm::vec3& impulse) override;
+
+    bool Raycast(const glm::vec3& origin,
+                 const glm::vec3& direction,
+                 float maxDistance,
+                 PhysicsRaycastHit& hit) const override;
+
+    void SyncKinematicBodiesToPhysics();
+    void SyncDynamicBodiesToTransforms();
+
+    [[nodiscard]] const glm::vec3& GetGravity() const { return m_Gravity; }
+    void SetGravity(const glm::vec3& gravity) { m_Gravity = gravity; }
+
+private:
+    struct BodyRecord {
+        bool alive{false};
+
+        PhysicsBodyHandle handle{};
+        PhysicsBodyDesc desc{};
+
+        PhysicsTransform previousTransform{};
+        PhysicsTransform currentTransform{};
+
+        glm::vec3 linearVelocity{0.0f};
+        glm::vec3 accumulatedForce{0.0f};
+
+        Rigidbody* rigidbody{nullptr};
+    };
+
+    [[nodiscard]] BodyRecord* FindBody(PhysicsBodyHandle body);
+    [[nodiscard]] const BodyRecord* FindBody(PhysicsBodyHandle body) const;
+
+    [[nodiscard]] float GetApproxBoundingRadius(const BodyRecord& body) const;
+    [[nodiscard]] static bool RaySphere(const glm::vec3& origin,
+                                        const glm::vec3& dirNormalized,
+                                        const glm::vec3& center,
+                                        float radius,
+                                        float maxDistance,
+                                        float& outDistance);
+
+    glm::vec3 m_Gravity{0.0f, -9.81f, 0.0f};
+
+    std::vector<BodyRecord> m_Bodies;
+    std::uint32_t m_NextId{0};
+};

destrum/include/destrum/Scene/Scene.h

@@ -6,6 +6,8 @@
 #include <destrum/Event.h>
 #include <destrum/Scene/SceneManager.h>
 
+#include "destrum/Physics/PhysicsSceneBridge.h"
+
 class GameObject;
 
 class Scene final {
@@ -19,7 +21,7 @@ public:
     void Load();
 
     void Update();
-    void FixedUpdate();
+    void FixedUpdate(float dt);
     void LateUpdate();
     void Render(const RenderContext& ctx) const;
     void RenderImgui();
@@ -62,9 +64,13 @@ public:
 
     Event<> OnSceneLoaded;
 
+    PhysicsSceneBridge& GetPhysics() { return m_Physics; }
 private:
     explicit Scene(const std::string& name);
 
+    PhysicsSceneBridge m_Physics{std::make_unique<SimplePhysicsWorld>()};
+
+
     std::string m_name;
     std::vector<std::shared_ptr<GameObject>> m_objects{};
     std::vector<std::shared_ptr<GameObject>> m_pendingAdditions{};

destrum/include/destrum/Scene/SceneManager.h

@@ -19,7 +19,7 @@ public:
     Scene& GetCurrentScene() const { return *m_scenes[m_ActiveSceneIndex]; }
 
     void Update();
-    void FixedUpdate();
+    void FixedUpdate(float dt);
     void LateUpdate();
 
     void Render(const RenderContext& ctx);

destrum/src/App.cpp

@@ -12,10 +12,12 @@
 
 #include <Jolt/Jolt.h>
 
-App::App() {
+App::App()
+{
 }
 
-void App::init(const AppParams &params) {
+void App::init(const AppParams& params)
+{
     m_params = params;
 
     AssetFS::GetInstance().Init(params.exeDir);
@@ -33,7 +35,8 @@ void App::init(const AppParams &params) {
         SDL_WINDOW_VULKAN);
 
     SDL_SetWindowResizable(window, SDL_TRUE);
-    if (!window) {
+    if (!window)
+    {
         spdlog::error("Failed to create window. SDL Error: {}", SDL_GetError());
         std::exit(1);
     }
@@ -48,7 +51,8 @@ void App::init(const AppParams &params) {
     customInit();
 }
 
-void App::run() {
+void App::run()
+{
     Time::GetInstance().Update(); // initialize delta timing
 
     const float fixedDt = static_cast<float>(Time::GetInstance().FixedDeltaTime());
@@ -56,14 +60,16 @@ void App::run() {
     float accumulator = 0.0f;
 
     isRunning = true;
-    while (isRunning) {
+    while (isRunning)
+    {
         // ---- Update timing ---
         Time::GetInstance().Update();
         float dt = static_cast<float>(Time::GetInstance().DeltaTime());
 
         if (dt > 0.25f) dt = 0.25f;
 
-        if (dt > 0.0f) {
+        if (dt > 0.0f)
+        {
             float newFPS = 1.0f / dt;
             avgFPS = std::lerp(avgFPS, newFPS, 0.1f);
         }
@@ -75,16 +81,21 @@ void App::run() {
 
 
         SDL_Event event;
-        while (SDL_PollEvent(&event)) {
+        while (SDL_PollEvent(&event))
+        {
             imguiPass.handleEvent(event);
-            if (event.type == SDL_QUIT) {
+            if (event.type == SDL_QUIT)
+            {
                 isRunning = false;
                 break;
             }
-            if (event.type == SDL_WINDOWEVENT) {
-                switch (event.window.event) {
-                    case SDL_WINDOWEVENT_SIZE_CHANGED:
-                    case SDL_WINDOWEVENT_RESIZED: {
+            if (event.type == SDL_WINDOWEVENT)
+            {
+                switch (event.window.event)
+                {
+                case SDL_WINDOWEVENT_SIZE_CHANGED:
+                case SDL_WINDOWEVENT_RESIZED:
+                    {
                         resizePending = true;
                         lastResizeTime = std::chrono::steady_clock::now();
                         break;
@@ -92,22 +103,24 @@ void App::run() {
                 }
             }
             const bool mouseEvent =
-                    event.type == SDL_MOUSEBUTTONDOWN ||
-                    event.type == SDL_MOUSEBUTTONUP ||
-                    event.type == SDL_MOUSEMOTION ||
-                    event.type == SDL_MOUSEWHEEL;
+                event.type == SDL_MOUSEBUTTONDOWN ||
+                event.type == SDL_MOUSEBUTTONUP ||
+                event.type == SDL_MOUSEMOTION ||
+                event.type == SDL_MOUSEWHEEL;
 
             const bool keyboardEvent =
-                    event.type == SDL_KEYDOWN ||
-                    event.type == SDL_KEYUP ||
-                    event.type == SDL_TEXTINPUT;
+                event.type == SDL_KEYDOWN ||
+                event.type == SDL_KEYUP ||
+                event.type == SDL_TEXTINPUT;
 
             const bool capturedByImgui =
-                    (mouseEvent && imguiPass.wantsMouse()) ||
-                    (keyboardEvent && imguiPass.wantsKeyboard());
+                (mouseEvent && imguiPass.wantsMouse()) ||
+                (keyboardEvent && imguiPass.wantsKeyboard());
 
-            if (!capturedByImgui) {
-                if (InputManager::GetInstance().ProcessEvent(event)) {
+            if (!capturedByImgui)
+            {
+                if (InputManager::GetInstance().ProcessEvent(event))
+                {
                     isRunning = false;
                 }
             }
@@ -123,13 +136,12 @@ void App::run() {
 
         imguiPass.endFrame();
         int steps = 0;
-        while (accumulator >= fixedDt && steps < maxSteps) {
+        while (accumulator >= fixedDt && steps < maxSteps)
+        {
             // physics.Update(fixedDt);
-
-            SDL_SetWindowTitle(
-                window,
-                fmt::format("{} - FPS: {:.2f}", m_params.windowTitle, avgFPS).c_str()
-            );
+            customFixedUpdate(fixedDt);
+            // physics.Step(fixedDt);
+            // physics.SyncTransforms();
 
             accumulator -= fixedDt;
             steps++;
@@ -138,11 +150,13 @@ void App::run() {
 
         const float alpha = accumulator / fixedDt;
 
-        if (gfxDevice.needsSwapchainRecreate() || resizePending) {
+        if (gfxDevice.needsSwapchainRecreate() || resizePending)
+        {
             auto now = std::chrono::steady_clock::now();
 
             if (resizePending &&
-                now - lastResizeTime < std::chrono::milliseconds(100)) {
+                now - lastResizeTime < std::chrono::milliseconds(100))
+            {
                 continue;
             }
 
@@ -150,7 +164,8 @@ void App::run() {
             int h = 0;
             SDL_Vulkan_GetDrawableSize(window, &w, &h);
 
-            if (w == 0 || h == 0) {
+            if (w == 0 || h == 0)
+            {
                 continue;
             }
 
@@ -166,9 +181,11 @@ void App::run() {
         customDraw();
 
 
-        if (frameLimit) {
+        if (frameLimit)
+        {
             auto sleepTime = Time::GetInstance().SleepDuration();
-            if (sleepTime.count() > 0) {
+            if (sleepTime.count() > 0)
+            {
                 std::this_thread::sleep_for(sleepTime);
             }
         }
@@ -177,7 +194,8 @@ void App::run() {
     gfxDevice.waitIdle();
 }
 
-void App::cleanup() {
+void App::cleanup()
+{
     spdlog::info("Cleaning up");
     customCleanup();
 }

destrum/src/Components/Physics/BoxCollider.cpp

@@ -0,0 +1 @@
+#include <destrum/Components/Physics/BoxCollider.h>

destrum/src/Components/Physics/Rigidbody.cpp

@@ -0,0 +1,45 @@
+#include <destrum/Components/Physics/Rigidbody.h>
+
+#include <destrum/Physics/PhysicsWorld.h>
+
+void Rigidbody::AttachPhysicsBody(PhysicsWorld* world, PhysicsBodyHandle body) {
+    m_World = world;
+    m_Body = body;
+}
+
+void Rigidbody::DetachPhysicsBody() {
+    m_World = nullptr;
+    m_Body.Reset();
+}
+
+void Rigidbody::AddForce(const glm::vec3& force) {
+    if (!HasPhysicsBody()) {
+        return;
+    }
+
+    m_World->AddForce(m_Body, force);
+}
+
+void Rigidbody::AddImpulse(const glm::vec3& impulse) {
+    if (!HasPhysicsBody()) {
+        return;
+    }
+
+    m_World->AddImpulse(m_Body, impulse);
+}
+
+void Rigidbody::SetLinearVelocity(const glm::vec3& velocity) {
+    if (!HasPhysicsBody()) {
+        return;
+    }
+
+    m_World->SetLinearVelocity(m_Body, velocity);
+}
+
+glm::vec3 Rigidbody::GetLinearVelocity() const {
+    if (!HasPhysicsBody()) {
+        return glm::vec3{0.0f};
+    }
+
+    return m_World->GetLinearVelocity(m_Body);
+}

destrum/src/Physics/PhysicsSceneBridge.cpp

@@ -0,0 +1,35 @@
+#include <destrum/Physics/PhysicsSceneBridge.h>
+
+#include <destrum/Components/Physics/Rigidbody.h>
+#include <destrum/ObjectModel/GameObject.h>
+
+PhysicsSceneBridge::PhysicsSceneBridge(std::unique_ptr<PhysicsWorld> world)
+    : m_World(std::move(world)) {
+}
+
+void PhysicsSceneBridge::RegisterGameObject(GameObject& object) {
+    if (auto* rb = object.GetComponent<Rigidbody>()) {
+        if (!rb->HasPhysicsBody()) {
+            m_World->RegisterRigidbody(*rb);
+        }
+    }
+}
+
+void PhysicsSceneBridge::UnregisterGameObject(GameObject& object) {
+    if (auto* rb = object.GetComponent<Rigidbody>()) {
+        if (rb->HasPhysicsBody()) {
+            m_World->UnregisterRigidbody(*rb);
+        }
+    }
+}
+
+void PhysicsSceneBridge::FixedUpdate(float fixedDt) {
+    if (auto* simple = dynamic_cast<SimplePhysicsWorld*>(m_World.get())) {
+        simple->SyncKinematicBodiesToPhysics();
+        simple->Step(fixedDt);
+        simple->SyncDynamicBodiesToTransforms();
+        return;
+    }
+
+    m_World->Step(fixedDt);
+}

destrum/src/Physics/PhysicsWorld.cpp

@@ -0,0 +1,62 @@
+#include <destrum/Physics/PhysicsWorld.h>
+
+#include <stdexcept>
+
+#include <destrum/Components/Physics/Rigidbody.h>
+#include <destrum/Components/Physics/Collider.h>
+#include <destrum/ObjectModel/GameObject.h>
+#include <destrum/ObjectModel/Transform.h>
+#include <destrum/Components/Physics/Rigidbody.h>
+
+void PhysicsWorld::RegisterRigidbody(Rigidbody& rigidbody) {
+    GameObject* owner = rigidbody.GetGameObject();
+    Transform& transform = owner->GetTransform();
+
+    auto* collider = owner->GetComponent<Collider>();
+    if (!collider) {
+        throw std::runtime_error("Rigidbody requires a Collider on the same GameObject for now.");
+    }
+
+    PhysicsBodyDesc desc{};
+    desc.owner = owner;
+    desc.transform.position = transform.GetWorldPosition();
+    desc.transform.rotation = transform.GetWorldRotation();
+    desc.shape = collider->BuildPhysicsShape();
+
+    desc.type = rigidbody.GetType();
+    desc.mass = rigidbody.GetMass();
+    desc.useGravity = rigidbody.UsesGravity();
+    desc.allowSleep = rigidbody.AllowsSleep();
+    desc.material.friction = rigidbody.GetFriction();
+    desc.material.restitution = rigidbody.GetRestitution();
+
+    PhysicsBodyHandle handle = CreateBody(desc);
+    rigidbody.AttachPhysicsBody(this, handle);
+}
+
+void PhysicsWorld::UnregisterRigidbody(Rigidbody& rigidbody) {
+    PhysicsBodyHandle handle = rigidbody.GetBody();
+
+    if (handle.IsValid()) {
+        DestroyBody(handle);
+    }
+
+    rigidbody.DetachPhysicsBody();
+}
+
+void PhysicsWorld::SyncKinematicBodiesToPhysics() {
+    // Backend-independent sync is intentionally not possible here because
+    // PhysicsWorld does not own the list of active rigidbodies.
+    //
+    // Use SimplePhysicsWorld as a reference implementation.
+    //
+    // If you use Jolt/PhysX/Bullet later, keep a body table in the backend:
+    // handle -> { GameObject*, Rigidbody* }.
+}
+
+void PhysicsWorld::SyncDynamicBodiesToTransforms() {
+    // Backend-independent sync is intentionally not possible here because
+    // PhysicsWorld does not own the list of active rigidbodies.
+    //
+    // Use SimplePhysicsWorld as a reference implementation.
+}

destrum/src/Physics/SimplePhysicsWorld.cpp

@@ -0,0 +1,277 @@
+#include <destrum/Physics/SimplePhysicsWorld.h>
+
+#include <algorithm>
+#include <cmath>
+#include <limits>
+
+#include <destrum/Components/Physics/Rigidbody.h>
+#include <destrum/ObjectModel/GameObject.h>
+#include <destrum/ObjectModel/Transform.h>
+
+SimplePhysicsWorld::SimplePhysicsWorld(const glm::vec3& gravity)
+    : m_Gravity(gravity) {
+}
+
+PhysicsBodyHandle SimplePhysicsWorld::CreateBody(const PhysicsBodyDesc& desc) {
+    BodyRecord record{};
+    record.alive = true;
+    record.handle = PhysicsBodyHandle{m_NextId++};
+    record.desc = desc;
+    record.previousTransform = desc.transform;
+    record.currentTransform = desc.transform;
+
+    if (desc.owner) {
+        record.rigidbody = desc.owner->GetComponent<Rigidbody>();
+    }
+
+    m_Bodies.emplace_back(record);
+    return record.handle;
+}
+
+void SimplePhysicsWorld::DestroyBody(PhysicsBodyHandle body) {
+    if (BodyRecord* record = FindBody(body)) {
+        record->alive = false;
+        record->rigidbody = nullptr;
+    }
+}
+
+void SimplePhysicsWorld::SetBodyTransform(PhysicsBodyHandle body, const PhysicsTransform& transform) {
+    BodyRecord* record = FindBody(body);
+    if (!record) {
+        return;
+    }
+
+    record->previousTransform = record->currentTransform;
+    record->currentTransform = transform;
+}
+
+PhysicsTransform SimplePhysicsWorld::GetBodyTransform(PhysicsBodyHandle body) const {
+    const BodyRecord* record = FindBody(body);
+    if (!record) {
+        return {};
+    }
+
+    return record->currentTransform;
+}
+
+void SimplePhysicsWorld::SetLinearVelocity(PhysicsBodyHandle body, const glm::vec3& velocity) {
+    BodyRecord* record = FindBody(body);
+    if (!record) {
+        return;
+    }
+
+    record->linearVelocity = velocity;
+}
+
+glm::vec3 SimplePhysicsWorld::GetLinearVelocity(PhysicsBodyHandle body) const {
+    const BodyRecord* record = FindBody(body);
+    if (!record) {
+        return glm::vec3{0.0f};
+    }
+
+    return record->linearVelocity;
+}
+
+void SimplePhysicsWorld::AddForce(PhysicsBodyHandle body, const glm::vec3& force) {
+    BodyRecord* record = FindBody(body);
+    if (!record || record->desc.type != RigidbodyType::Dynamic) {
+        return;
+    }
+
+    record->accumulatedForce += force;
+}
+
+void SimplePhysicsWorld::AddImpulse(PhysicsBodyHandle body, const glm::vec3& impulse) {
+    BodyRecord* record = FindBody(body);
+    if (!record || record->desc.type != RigidbodyType::Dynamic) {
+        return;
+    }
+
+    const float invMass = record->desc.mass > 0.0f ? 1.0f / record->desc.mass : 0.0f;
+    record->linearVelocity += impulse * invMass;
+}
+
+void SimplePhysicsWorld::Step(float fixedDt) {
+    if (fixedDt <= 0.0f) {
+        return;
+    }
+
+    for (BodyRecord& body : m_Bodies) {
+        if (!body.alive) {
+            continue;
+        }
+
+        body.previousTransform = body.currentTransform;
+
+        if (body.desc.type != RigidbodyType::Dynamic) {
+            continue;
+        }
+
+        const float invMass = body.desc.mass > 0.0f ? 1.0f / body.desc.mass : 0.0f;
+
+        glm::vec3 acceleration{0.0f};
+
+        if (body.desc.useGravity) {
+            acceleration += m_Gravity;
+        }
+
+        acceleration += body.accumulatedForce * invMass;
+
+        // Semi-implicit Euler.
+        body.linearVelocity += acceleration * fixedDt;
+        body.currentTransform.position += body.linearVelocity * fixedDt;
+
+        body.accumulatedForce = glm::vec3{0.0f};
+    }
+
+    // Compact dead records occasionally.
+    m_Bodies.erase(
+        std::remove_if(m_Bodies.begin(), m_Bodies.end(),
+            [](const BodyRecord& body) { return !body.alive; }),
+        m_Bodies.end());
+}
+
+void SimplePhysicsWorld::SyncKinematicBodiesToPhysics() {
+    for (BodyRecord& body : m_Bodies) {
+        if (!body.alive || body.desc.type != RigidbodyType::Kinematic || !body.desc.owner) {
+            continue;
+        }
+
+        Transform& transform = body.desc.owner->GetTransform();
+
+        body.previousTransform = body.currentTransform;
+        body.currentTransform.position = transform.GetWorldPosition();
+        body.currentTransform.rotation = transform.GetWorldRotation();
+    }
+}
+
+void SimplePhysicsWorld::SyncDynamicBodiesToTransforms() {
+    for (BodyRecord& body : m_Bodies) {
+        if (!body.alive || body.desc.type != RigidbodyType::Dynamic || !body.desc.owner) {
+            continue;
+        }
+
+        Transform& transform = body.desc.owner->GetTransform();
+        transform.SetWorldPosition(body.currentTransform.position);
+        transform.SetWorldRotation(body.currentTransform.rotation);
+    }
+}
+
+bool SimplePhysicsWorld::Raycast(const glm::vec3& origin,
+                                 const glm::vec3& direction,
+                                 float maxDistance,
+                                 PhysicsRaycastHit& hit) const {
+    if (maxDistance <= 0.0f) {
+        return false;
+    }
+
+    const float len = glm::length(direction);
+    if (len <= 0.00001f) {
+        return false;
+    }
+
+    const glm::vec3 dir = direction / len;
+
+    bool found = false;
+    float bestDistance = std::numeric_limits<float>::max();
+
+    for (const BodyRecord& body : m_Bodies) {
+        if (!body.alive || body.desc.shape.type == PhysicsShapeType::None) {
+            continue;
+        }
+
+        float distance = 0.0f;
+        const float radius = GetApproxBoundingRadius(body);
+        const glm::vec3 center = body.currentTransform.position + body.desc.shape.centerOffset;
+
+        if (RaySphere(origin, dir, center, radius, maxDistance, distance)) {
+            if (distance < bestDistance) {
+                bestDistance = distance;
+                found = true;
+
+                hit.object = body.desc.owner;
+                hit.body = body.handle;
+                hit.distance = distance;
+                hit.point = origin + dir * distance;
+
+                const glm::vec3 n = hit.point - center;
+                hit.normal = glm::length(n) > 0.00001f ? glm::normalize(n) : glm::vec3{0.0f, 1.0f, 0.0f};
+            }
+        }
+    }
+
+    return found;
+}
+
+SimplePhysicsWorld::BodyRecord* SimplePhysicsWorld::FindBody(PhysicsBodyHandle body) {
+    for (BodyRecord& record : m_Bodies) {
+        if (record.alive && record.handle == body) {
+            return &record;
+        }
+    }
+
+    return nullptr;
+}
+
+const SimplePhysicsWorld::BodyRecord* SimplePhysicsWorld::FindBody(PhysicsBodyHandle body) const {
+    for (const BodyRecord& record : m_Bodies) {
+        if (record.alive && record.handle == body) {
+            return &record;
+        }
+    }
+
+    return nullptr;
+}
+
+float SimplePhysicsWorld::GetApproxBoundingRadius(const BodyRecord& body) const {
+    const PhysicsShapeDesc& shape = body.desc.shape;
+
+    switch (shape.type) {
+        case PhysicsShapeType::Box:
+            return glm::length(shape.halfExtents);
+
+        case PhysicsShapeType::Sphere:
+            return shape.radius;
+
+        case PhysicsShapeType::Capsule:
+            return shape.height * 0.5f;
+
+        case PhysicsShapeType::None:
+        default:
+            return 0.0f;
+    }
+}
+
+bool SimplePhysicsWorld::RaySphere(const glm::vec3& origin,
+                                   const glm::vec3& dirNormalized,
+                                   const glm::vec3& center,
+                                   float radius,
+                                   float maxDistance,
+                                   float& outDistance) {
+    const glm::vec3 oc = origin - center;
+
+    const float a = glm::dot(dirNormalized, dirNormalized);
+    const float b = 2.0f * glm::dot(oc, dirNormalized);
+    const float c = glm::dot(oc, oc) - radius * radius;
+
+    const float discriminant = b * b - 4.0f * a * c;
+    if (discriminant < 0.0f) {
+        return false;
+    }
+
+    const float sqrtDisc = std::sqrt(discriminant);
+    const float t0 = (-b - sqrtDisc) / (2.0f * a);
+    const float t1 = (-b + sqrtDisc) / (2.0f * a);
+
+    float t = t0;
+    if (t < 0.0f) {
+        t = t1;
+    }
+
+    if (t < 0.0f || t > maxDistance) {
+        return false;
+    }
+
+    outDistance = t;
+    return true;
+}

destrum/src/Scene/Scene.cpp

@@ -57,12 +57,13 @@ void Scene::Update() {
     }
 }
 
-void Scene::FixedUpdate() {
+void Scene::FixedUpdate(float dt) {
     for (const auto& object: m_objects) {
         if (object->IsActiveInHierarchy()) {
             object->FixedUpdate();
         }
     }
+    m_Physics.FixedUpdate(dt);
 }
 
 void Scene::LateUpdate() {

destrum/src/Scene/SceneManager.cpp

@@ -8,8 +8,8 @@ void SceneManager::Update() {
     m_scenes[m_ActiveSceneIndex]->Update();
 }
 
-void SceneManager::FixedUpdate() {
-    m_scenes[m_ActiveSceneIndex]->FixedUpdate();
+void SceneManager::FixedUpdate(float dt) {
+    m_scenes[m_ActiveSceneIndex]->FixedUpdate(dt);
 }
 
 void SceneManager::LateUpdate() {