feat: add moving platform support + fix jolt

destrum/include/destrum/Physics/JoltPhysicsWorld.h

@@ -35,7 +35,7 @@ public:
 
     void Step(float fixedDt) override;
 
-    void SyncKinematicBodiesToPhysics() override;
+    void SyncKinematicBodiesToPhysics(float fixedDt) override;
     void SyncDynamicBodiesToTransforms() override;
 
     PhysicsBodyHandle CreateBody(const PhysicsBodyDesc& desc) override;

destrum/include/destrum/Physics/PhysicsWorld.h

@@ -29,9 +29,9 @@ public:
 
     virtual void Step(float fixedDt) = 0;
 
-    // - Kinematic: Transform -> physics body before Step()
+    // - Kinematic: moved towards its Transform over the step, so it has a velocity
     // - Dynamic: physics body -> Transform after Step()
-    virtual void SyncKinematicBodiesToPhysics();
+    virtual void SyncKinematicBodiesToPhysics(float fixedDt);
     virtual void SyncDynamicBodiesToTransforms();
 
     virtual PhysicsBodyHandle CreateBody(const PhysicsBodyDesc& desc) = 0;

destrum/include/destrum/Physics/SimplePhysicsWorld.h

@@ -49,7 +49,7 @@ public:
                  PhysicsRaycastHit& hit,
                  PhysicsBodyHandle ignoreBody = {}) const override;
 
-    void SyncKinematicBodiesToPhysics();
+    void SyncKinematicBodiesToPhysics(float fixedDt) override;
     void SyncDynamicBodiesToTransforms();
 
     [[nodiscard]] const glm::vec3& GetGravity() const { return m_Gravity; }

destrum/src/Physics/JoltPhysicsWorld.cpp

@@ -548,7 +548,7 @@ public:
         return events;
     }
 
-    void SyncKinematicBodiesToPhysics()
+    void SyncKinematicBodiesToPhysics(float fixedDt)
     {
         BodyInterface& bodyInterface = m_PhysicsSystem.GetBodyInterface();
 
@@ -562,11 +562,11 @@ public:
 
             Transform& transform = record.desc.owner->GetTransform();
 
-            bodyInterface.SetPositionAndRotation(
+            bodyInterface.MoveKinematic(
                 record.bodyID,
                 ToJoltRVec3(transform.GetWorldPosition()),
                 ToJoltQuat(transform.GetWorldRotation()),
-                EActivation::Activate);
+                fixedDt);
         }
     }
 
@@ -819,9 +819,9 @@ void JoltPhysicsWorld::Step(float fixedDt)
     m_Impl->Step(fixedDt);
 }
 
-void JoltPhysicsWorld::SyncKinematicBodiesToPhysics()
+void JoltPhysicsWorld::SyncKinematicBodiesToPhysics(float fixedDt)
 {
-    m_Impl->SyncKinematicBodiesToPhysics();
+    m_Impl->SyncKinematicBodiesToPhysics(fixedDt);
 }
 
 void JoltPhysicsWorld::SyncDynamicBodiesToTransforms()

destrum/src/Physics/PhysicsSceneBridge.cpp

@@ -35,7 +35,7 @@ void PhysicsSceneBridge::RefreshGameObject(GameObject& object) {
 
 void PhysicsSceneBridge::FixedUpdate(float fixedDt) {
     if (!m_World) return;
-    m_World->SyncKinematicBodiesToPhysics();
+    m_World->SyncKinematicBodiesToPhysics(fixedDt);
     m_World->Step(fixedDt);
 
     for (const auto& event : m_World->ConsumeTriggerEvents()) {

destrum/src/Physics/PhysicsWorld.cpp

@@ -115,7 +115,7 @@ void PhysicsWorld::UnregisterRigidbody(Rigidbody& rigidbody) {
     rigidbody.DetachPhysicsBody();
 }
 
-void PhysicsWorld::SyncKinematicBodiesToPhysics() {
+void PhysicsWorld::SyncKinematicBodiesToPhysics(float) {
     // Backend-independent sync is intentionally not possible here because
     // PhysicsWorld does not own the list of active rigidbodies.
 }

destrum/src/Physics/SimplePhysicsWorld.cpp

@@ -134,7 +134,7 @@ void SimplePhysicsWorld::Step(float fixedDt) {
         m_Bodies.end());
 }
 
-void SimplePhysicsWorld::SyncKinematicBodiesToPhysics() {
+void SimplePhysicsWorld::SyncKinematicBodiesToPhysics(float fixedDt) {
     for (BodyRecord& body : m_Bodies) {
         if (!body.alive || body.desc.type != RigidbodyType::Kinematic || !body.desc.owner ||
             body.desc.owner->IsBeingDestroyed() || !body.desc.owner->IsActiveInHierarchy()) {
@@ -146,6 +146,9 @@ void SimplePhysicsWorld::SyncKinematicBodiesToPhysics() {
         body.previousTransform = body.currentTransform;
         body.currentTransform.position = transform.GetWorldPosition();
         body.currentTransform.rotation = transform.GetWorldRotation();
+        body.linearVelocity = fixedDt > 0.0f
+            ? (body.currentTransform.position - body.previousTransform.position) / fixedDt
+            : glm::vec3{0.0f};
     }
 }
 

lightkeeper/CMakeLists.txt

@@ -18,6 +18,7 @@ set(GAME_SRC
     src/components/Interactable.cpp
     src/components/InteractableButton.cpp
     src/components/LightToggle.cpp
+    src/components/MovingPlatform.cpp
     src/components/PrintComponent.cpp
     src/components/TriggerLoggerComponent.cpp
 )

lightkeeper/include/components/FirstPersonController.h

@@ -1,6 +1,8 @@
 #ifndef LIGHTKEEPER_FIRSTPERSONCONTROLLER_H
 #define LIGHTKEEPER_FIRSTPERSONCONTROLLER_H
 
+#include <optional>
+
 #include <glm/glm.hpp>
 #include <destrum/Input/InputManager.h>
 #include <destrum/ObjectModel/Component.h>
@@ -45,7 +47,12 @@ public:
     void SetPossessed(bool possessed);
 
 private:
-    [[nodiscard]] bool CheckGrounded() const;
+    struct GroundContact {
+        glm::vec3 normal;
+        glm::vec3 velocity;
+    };
+
+    [[nodiscard]] std::optional<GroundContact> FindGround() const;
     [[nodiscard]] glm::vec3 GetWishDirection() const;
     [[nodiscard]] Interactable* FindFocusedInteractable() const;
 
@@ -67,11 +74,14 @@ private:
     float m_CoyoteTime{0.1f};
     float m_JumpBufferTime{0.12f};
     float m_InteractDistance{3.0f};
+    float m_MaxSlopeAngle{glm::radians(50.0f)};
+    float m_GroundStickSpeed{2.0f};
 
     Interactable* m_FocusedInteractable{nullptr};
 
     bool m_Possessed{false};
     bool m_Grounded{false};
+    glm::vec3 m_GroundNormal{0.0f, 1.0f, 0.0f};
     bool m_JumpHeld{false};
     float m_CoyoteTimer{0.0f};
     float m_JumpBufferTimer{0.0f};

lightkeeper/include/components/GameComponentList.h

@@ -5,6 +5,7 @@
 #include <components/FirstPersonController.h>
 #include <components/InteractableButton.h>
 #include <components/LightToggle.h>
+#include <components/MovingPlatform.h>
 #include <components/PrintComponent.h>
 #include <components/TriggerLoggerComponent.h>
 
@@ -13,6 +14,7 @@
     X(FirstPersonController) \
     X(InteractableButton) \
     X(LightToggle) \
+    X(MovingPlatform) \
     X(PrintComponent) \
     X(TriggerLoggerComponent)
 

lightkeeper/include/components/MovingPlatform.h

@@ -0,0 +1,38 @@
+#ifndef LIGHTKEEPER_MOVINGPLATFORM_H
+#define LIGHTKEEPER_MOVINGPLATFORM_H
+
+#include <destrum/ObjectModel/Component.h>
+
+#include <glm/vec3.hpp>
+
+class MovingPlatform final : public Component {
+public:
+    explicit MovingPlatform(GameObject& parent);
+
+    std::string GetTypeName() const override { return "MovingPlatform"; }
+
+    void Start() override;
+    void Update(float dt) override;
+
+    nlohmann::json Serialize() const override;
+    void Deserialize(const nlohmann::json& data) override;
+    void ImGuiInspector() override;
+
+    void SetTravelOffset(const glm::vec3& offset) { m_TravelOffset = offset; }
+    void SetTravelDuration(float seconds) { m_TravelDuration = seconds; }
+    void SetPauseDuration(float seconds) { m_PauseDuration = seconds; }
+
+private:
+    [[nodiscard]] float GetTravelProgress() const;
+    [[nodiscard]] glm::vec3 GetOffsetAt(float progress) const;
+
+    glm::vec3 m_TravelOffset{8.0f, 0.0f, 0.0f};
+    float m_TravelDuration{4.0f};
+    float m_PauseDuration{1.0f};
+
+    float m_ElapsedTime{0.0f};
+    glm::vec3 m_StartPosition{0.0f};
+    bool m_Started{false};
+};
+
+#endif // LIGHTKEEPER_MOVINGPLATFORM_H

lightkeeper/src/components/FirstPersonController.cpp

@@ -27,6 +27,16 @@ namespace {
         }
         return current + delta / distance * maxDelta;
     }
+
+    glm::vec3 ProjectOntoSlope(const glm::vec3& vector, const glm::vec3& slopeNormal)
+    {
+        const glm::vec3 projected = vector - slopeNormal * glm::dot(vector, slopeNormal);
+        const float projectedLength = glm::length(projected);
+        if (projectedLength < 1e-6f) {
+            return glm::vec3{0.0f};
+        }
+        return projected * (glm::length(vector) / projectedLength);
+    }
 }
 
 FirstPersonController::FirstPersonController(GameObject& parent)
@@ -130,22 +140,38 @@ void FirstPersonController::FixedUpdate(float fixedDt)
     m_PreviousPosition = GetTransform().GetWorldPosition();
     m_HasPreviousPosition = true;
 
-    glm::vec3 velocity = m_Rigidbody->GetLinearVelocity();
+    const std::optional<GroundContact> ground = FindGround();
+    const glm::vec3 groundVelocity = ground ? ground->velocity : glm::vec3{0.0f};
 
-    m_Grounded = velocity.y <= 0.1f && CheckGrounded();
+    // Movement happens relative to whatever is underneath, so moving platforms carry the player
+    glm::vec3 velocity = m_Rigidbody->GetLinearVelocity() - groundVelocity;
+
+    m_Grounded = ground.has_value() && glm::dot(velocity, ground->normal) <= 0.1f;
+    m_GroundNormal = m_Grounded ? ground->normal : glm::vec3{0.0f, 1.0f, 0.0f};
     m_CoyoteTimer = m_Grounded ? m_CoyoteTime : std::max(m_CoyoteTimer - fixedDt, 0.0f);
 
     const auto& input = InputManager::GetInstance();
     const bool sprinting = m_Possessed && input.IsKeyDown(SDL_SCANCODE_LSHIFT);
     const glm::vec3 wishVelocity = GetWishDirection() * (sprinting ? m_SprintSpeed : m_WalkSpeed);
 
-    const float acceleration = m_Grounded ? m_GroundAcceleration : m_AirAcceleration;
+    if (m_Grounded)
-    const glm::vec3 horizontal = MoveTowards(
+    {
-        glm::vec3{velocity.x, 0.0f, velocity.z},
+        const glm::vec3 velocityAlongSlope = velocity - m_GroundNormal * glm::dot(velocity, m_GroundNormal);
-        wishVelocity,
+        velocity = MoveTowards(
-        acceleration * fixedDt);
+            velocityAlongSlope,
-    velocity.x = horizontal.x;
+            ProjectOntoSlope(wishVelocity, m_GroundNormal),
-    velocity.z = horizontal.z;
+            m_GroundAcceleration * fixedDt);
+        velocity -= m_GroundNormal * m_GroundStickSpeed;
+    }
+    else
+    {
+        const glm::vec3 horizontal = MoveTowards(
+            glm::vec3{velocity.x, 0.0f, velocity.z},
+            wishVelocity,
+            m_AirAcceleration * fixedDt);
+        velocity.x = horizontal.x;
+        velocity.z = horizontal.z;
+    }
 
     if (m_JumpBufferTimer > 0.0f && m_CoyoteTimer > 0.0f)
     {
@@ -155,22 +181,25 @@ void FirstPersonController::FixedUpdate(float fixedDt)
         m_Grounded = false;
     }
 
-    // Falling faster than rising, and letting go of jump early cuts the jump short
+    if (!m_Grounded)
-    float gravity = m_Gravity;
-    if (velocity.y < 0.0f || !m_JumpHeld)
     {
-        gravity *= m_FallGravityMultiplier;
+        // Falling faster than rising, and letting go of jump early cuts the jump short
+        float gravity = m_Gravity;
+        if (velocity.y < 0.0f || !m_JumpHeld)
+        {
+            gravity *= m_FallGravityMultiplier;
+        }
+        velocity.y -= gravity * fixedDt;
     }
-    velocity.y -= gravity * fixedDt;
 
-    m_Rigidbody->SetLinearVelocity(velocity);
+    m_Rigidbody->SetLinearVelocity(velocity + groundVelocity);
 }
 
-bool FirstPersonController::CheckGrounded() const
+std::optional<FirstPersonController::GroundContact> FirstPersonController::FindGround() const
 {
     const auto* world = m_Rigidbody->GetPhysicsWorld();
     if (world == nullptr || m_Capsule == nullptr)
-        return false;
+        return std::nullopt;
 
     const glm::vec3 center = GetTransform().GetWorldPosition() + m_Capsule->GetCenterOffset();
     const float radius = m_Capsule->GetRadius();
@@ -187,6 +216,7 @@ bool FirstPersonController::CheckGrounded() const
 
     constexpr float startHeight = 0.2f;
     constexpr float probeDistance = 0.1f;
+    const float minWalkableNormalY = std::cos(m_MaxSlopeAngle);
     for (const glm::vec2& offset : offsets)
     {
         const glm::vec3 origin{center.x + offset.x, bottom + startHeight, center.z + offset.y};
@@ -194,12 +224,15 @@ bool FirstPersonController::CheckGrounded() const
         PhysicsRaycastHit hit{};
         if (world->Raycast(origin, glm::vec3{0.0f, -1.0f, 0.0f}, startHeight + probeDistance, hit,
                            m_Rigidbody->GetBody()) &&
-            hit.normal.y > 0.6f)
+            hit.normal.y >= minWalkableNormalY)
         {
-            return true;
+            return GroundContact{
+                .normal = glm::normalize(hit.normal),
+                .velocity = hit.body.IsValid() ? world->GetLinearVelocity(hit.body) : glm::vec3{0.0f},
+            };
         }
     }
-    return false;
+    return std::nullopt;
 }
 
 glm::vec3 FirstPersonController::GetWishDirection() const
@@ -243,9 +276,12 @@ void FirstPersonController::ImGuiInspector()
     ImGui::DragFloat("Coyote Time", &m_CoyoteTime, 0.005f, 0.0f, 1.0f);
     ImGui::DragFloat("Jump Buffer Time", &m_JumpBufferTime, 0.005f, 0.0f, 1.0f);
     ImGui::DragFloat("Interact Distance", &m_InteractDistance, 0.05f, 0.0f, 20.0f);
+    ImGui::SliderAngle("Max Slope Angle", &m_MaxSlopeAngle, 0.0f, 89.0f);
+    ImGui::DragFloat("Ground Stick Speed", &m_GroundStickSpeed, 0.05f, 0.0f, 20.0f);
     ImGui::DragFloat("Mouse Sensitivity", &m_MouseSensitivity, 0.0001f, 0.0f, 0.1f);
     ImGui::DragFloat("Eye Height", &m_EyeHeight, 0.01f, -2.0f, 2.0f);
     ImGui::Text("Grounded: %s", m_Grounded ? "yes" : "no");
+    ImGui::Text("Ground slope: %.1f deg", glm::degrees(std::acos(glm::clamp(m_GroundNormal.y, -1.0f, 1.0f))));
     ImGui::Text("Yaw: %.1f deg", glm::degrees(m_Yaw));
     ImGui::Text("Pitch: %.1f deg", glm::degrees(m_Pitch));
     if (bool possessed = m_Possessed; ImGui::Checkbox("Possessed", &possessed)) {
@@ -266,6 +302,8 @@ nlohmann::json FirstPersonController::Serialize() const
         {"coyoteTime", m_CoyoteTime},
         {"jumpBufferTime", m_JumpBufferTime},
         {"interactDistance", m_InteractDistance},
+        {"maxSlopeAngle", m_MaxSlopeAngle},
+        {"groundStickSpeed", m_GroundStickSpeed},
         {"mouseSensitivity", m_MouseSensitivity},
         {"eyeHeight", m_EyeHeight},
         {"yaw", m_Yaw},
@@ -285,6 +323,8 @@ void FirstPersonController::Deserialize(const nlohmann::json& data)
     m_CoyoteTime = data.value("coyoteTime", m_CoyoteTime);
     m_JumpBufferTime = data.value("jumpBufferTime", m_JumpBufferTime);
     m_InteractDistance = data.value("interactDistance", m_InteractDistance);
+    m_MaxSlopeAngle = data.value("maxSlopeAngle", m_MaxSlopeAngle);
+    m_GroundStickSpeed = data.value("groundStickSpeed", m_GroundStickSpeed);
     m_MouseSensitivity = data.value("mouseSensitivity", m_MouseSensitivity);
     m_EyeHeight = data.value("eyeHeight", m_EyeHeight);
     m_Yaw = data.value("yaw", m_Yaw);

lightkeeper/src/components/MovingPlatform.cpp

@@ -0,0 +1,79 @@
+#include <components/MovingPlatform.h>
+
+#include <algorithm>
+#include <cmath>
+
+#include <destrum/ObjectModel/GameObject.h>
+
+#include <imgui.h>
+
+MovingPlatform::MovingPlatform(GameObject& parent)
+    : Component(parent, "MovingPlatform")
+{
+}
+
+void MovingPlatform::Start()
+{
+    const glm::vec3 currentPosition = GetTransform().GetLocalPosition();
+    m_StartPosition = currentPosition - GetOffsetAt(GetTravelProgress());
+    m_Started = true;
+}
+
+void MovingPlatform::Update(float dt)
+{
+    if (!m_Started) {
+        return;
+    }
+
+    m_ElapsedTime += dt;
+    GetTransform().SetLocalPosition(m_StartPosition + GetOffsetAt(GetTravelProgress()));
+}
+
+float MovingPlatform::GetTravelProgress() const
+{
+    const float travelDuration = std::max(m_TravelDuration, 0.01f);
+    const float pauseDuration = std::max(m_PauseDuration, 0.0f);
+    const float legDuration = travelDuration + pauseDuration;
+
+    const float timeInCycle = std::fmod(m_ElapsedTime, legDuration * 2.0f);
+    const bool returning = timeInCycle >= legDuration;
+    const float timeInLeg = returning ? timeInCycle - legDuration : timeInCycle;
+
+    const float legProgress = std::clamp((timeInLeg - pauseDuration) / travelDuration, 0.0f, 1.0f);
+    return returning ? 1.0f - legProgress : legProgress;
+}
+
+glm::vec3 MovingPlatform::GetOffsetAt(float progress) const
+{
+    const float eased = progress * progress * (3.0f - 2.0f * progress);
+    return m_TravelOffset * eased;
+}
+
+nlohmann::json MovingPlatform::Serialize() const
+{
+    return {
+        {"travelOffset", {m_TravelOffset.x, m_TravelOffset.y, m_TravelOffset.z}},
+        {"travelDuration", m_TravelDuration},
+        {"pauseDuration", m_PauseDuration},
+        {"elapsedTime", m_ElapsedTime},
+    };
+}
+
+void MovingPlatform::Deserialize(const nlohmann::json& data)
+{
+    if (data.contains("travelOffset")) {
+        const auto& offset = data.at("travelOffset");
+        m_TravelOffset = {offset.at(0).get<float>(), offset.at(1).get<float>(), offset.at(2).get<float>()};
+    }
+    m_TravelDuration = std::max(data.value("travelDuration", m_TravelDuration), 0.01f);
+    m_PauseDuration = std::max(data.value("pauseDuration", m_PauseDuration), 0.0f);
+    m_ElapsedTime = std::max(data.value("elapsedTime", m_ElapsedTime), 0.0f);
+}
+
+void MovingPlatform::ImGuiInspector()
+{
+    ImGui::Text("Progress: %.0f%%", GetTravelProgress() * 100.0f);
+    ImGui::DragFloat3("Travel Offset", &m_TravelOffset.x, 0.05f);
+    ImGui::DragFloat("Travel Duration", &m_TravelDuration, 0.05f, 0.01f, 60.0f, "%.2f s");
+    ImGui::DragFloat("Pause Duration", &m_PauseDuration, 0.05f, 0.0f, 60.0f, "%.2f s");
+}

lightkeeper/src/scenes/MainScene.cpp

@@ -19,6 +19,7 @@
 #include <components/Door.h>
 #include <components/InteractableButton.h>
 #include <components/LightToggle.h>
+#include <components/MovingPlatform.h>
 #include <components/TriggerLoggerComponent.h>
 
 #include <glm/gtc/constants.hpp>
@@ -26,6 +27,7 @@
 
 #include <spdlog/spdlog.h>
 
+#include <cmath>
 #include <memory>
 #include <optional>
 #include <string>
@@ -124,10 +126,12 @@ namespace {
 
     GameObject* CreateBox(Scene& scene, GfxDevice& gfxDevice, RenderResources& resources,
                           const std::string& name, const glm::vec3& position, const glm::vec3& size,
-                          MaterialID materialID, RigidbodyType type)
+                          MaterialID materialID, RigidbodyType type,
+                          const glm::quat& rotation = glm::quat{1.0f, 0.0f, 0.0f, 0.0f})
     {
         GameObject* box = scene.CreateGameObject(name);
         box->GetTransform().SetWorldPosition(position);
+        box->GetTransform().SetWorldRotation(rotation);
 
         auto* boxMeshComp = box->AddComponent<MeshRendererComponent>();
         boxMeshComp->SetMeshID(resources.meshes().addMesh(gfxDevice, PrimitiveMeshes::MakeBox(size)));
@@ -221,6 +225,42 @@ namespace {
         button->AddComponent<InteractableButton>()->AddTarget(target);
     }
 
+    void CreateMovingPlatform(Scene& scene, GfxDevice& gfxDevice, RenderResources& resources)
+    {
+        const MaterialID rampMaterial = AddPrototypeMaterial(gfxDevice, resources, "Green", 0.6f);
+        const MaterialID platformMaterial = AddPrototypeMaterial(gfxDevice, resources, "Purple", 0.5f);
+
+        constexpr float laneZ = 2.0f;
+        constexpr float platformHeight = 1.0f;
+        constexpr float rampStartX = 9.0f;
+        constexpr float rampLength = 3.0f;
+        constexpr float rampThickness = 0.3f;
+        constexpr float travelDistance = 8.0f;
+        const glm::vec3 platformSize{3.0f, 0.3f, 3.0f};
+
+        const float platformTop = GroundHeight + platformHeight;
+        const glm::quat rampRotation =
+            glm::angleAxis(std::atan2(platformHeight, rampLength), glm::vec3{0.0f, 0.0f, 1.0f});
+        const glm::vec3 rampTopCenter{rampStartX + rampLength * 0.5f, GroundHeight + platformHeight * 0.5f, laneZ};
+        const glm::vec3 rampCenter = rampTopCenter - rampRotation * glm::vec3{0.0f, rampThickness * 0.5f, 0.0f};
+        const float rampSlopeLength = glm::length(glm::vec2{rampLength, platformHeight});
+
+        CreateBox(scene, gfxDevice, resources, "PlatformRamp", rampCenter,
+                  {rampSlopeLength, rampThickness, platformSize.z}, rampMaterial, RigidbodyType::Static,
+                  rampRotation);
+
+        const float platformStartX = rampStartX + rampLength + platformSize.x * 0.5f;
+        GameObject* platform = CreateBox(scene, gfxDevice, resources, "MovingPlatform",
+                                         {platformStartX, platformTop - platformSize.y * 0.5f, laneZ},
+                                         platformSize, platformMaterial, RigidbodyType::Kinematic);
+        platform->AddComponent<MovingPlatform>()->SetTravelOffset({travelDistance, 0.0f, 0.0f});
+
+        const float landingStartX = platformStartX + travelDistance + platformSize.x * 0.5f;
+        CreateBox(scene, gfxDevice, resources, "PlatformLanding",
+                  {landingStartX + 1.0f, GroundHeight + platformHeight * 0.5f, laneZ},
+                  {2.0f, platformHeight, platformSize.z}, rampMaterial, RigidbodyType::Static);
+    }
+
     struct WallOpening {
         float offset;
         float width;
@@ -467,6 +507,7 @@ MainSceneObjects BuildMainScene(Scene& scene, GfxDevice& gfxDevice, RenderResour
     const GameObject* door = CreateDoorway(scene, gfxDevice, resources);
     CreateButton(scene, gfxDevice, resources, *door);
     CreateHouse(scene, gfxDevice, resources);
+    CreateMovingPlatform(scene, gfxDevice, resources);
     CreatePlayer(scene, objects);
     LoadSpawnBallResources(gfxDevice, resources, objects);
 

tests/destrum_tests.cpp

@@ -540,6 +540,48 @@ namespace {
               "a frustum entirely behind the camera must not overlap");
     }
 
+    void testKinematicBodiesMoveWithVelocity()
+    {
+        constexpr float fixedDt = 1.0f / 60.0f;
+        Scene& scene = SceneManager::GetInstance().CreateScene("kinematic-velocity");
+
+        GameObject* platform = scene.CreateGameObject("platform");
+        platform->AddComponent<BoxCollider>(glm::vec3{2.0f, 0.25f, 2.0f});
+        auto* platformBody = platform->AddComponent<Rigidbody>();
+        platformBody->SetType(RigidbodyType::Kinematic);
+
+        GameObject* crate = scene.CreateGameObject("crate");
+        crate->GetTransform().SetWorldPosition({0.0f, 0.76f, 0.0f});
+        crate->AddComponent<BoxCollider>(glm::vec3{0.5f});
+        auto* crateBody = crate->AddComponent<Rigidbody>();
+        crateBody->SetFriction(1.0f);
+        crateBody->SetAllowSleep(false);
+
+        scene.CommitPendingAdditions();
+        scene.GetPhysics().RefreshGameObject(*platform);
+        scene.GetPhysics().RefreshGameObject(*crate);
+
+        for (int step = 0; step < 30; ++step) {
+            scene.FixedUpdate(fixedDt);
+        }
+        check(glm::length(platformBody->GetLinearVelocity()) < 0.001f,
+              "a kinematic body that is not moved must have no velocity");
+
+        constexpr float platformSpeed = 2.0f;
+        for (int step = 0; step < 60; ++step) {
+            platform->GetTransform().SetWorldPosition(
+                platform->GetTransform().GetWorldPosition() + glm::vec3{platformSpeed * fixedDt, 0.0f, 0.0f});
+            scene.FixedUpdate(fixedDt);
+        }
+
+        check(close(platformBody->GetLinearVelocity().x, platformSpeed),
+              "a kinematic body moved through its transform must get the matching velocity");
+        check(crate->GetTransform().GetWorldPosition().x > 1.5f,
+              "a dynamic body resting on a moving kinematic platform must be carried along");
+
+        SceneManager::GetInstance().Destroy();
+    }
+
     void testRenderer2DShapes()
     {
         auto& r2d = Renderer2D::GetInstance();
@@ -1335,6 +1377,7 @@ int main()
     testColliderCenterOffset();
     testCapsuleColliderDebugLines();
     testFrustumFromViewProj();
+    testKinematicBodiesMoveWithVelocity();
     testRenderer2DShapes();
     testFontAtlasAndLayout();
     std::cout << "destrum tests passed\n";