feat: move fps and deltatime calculations in core engine

engine/include/engine/app/app.h

@@ -3,6 +3,8 @@
 
 #include "engine/scene/scene.h"
 #include "engine/window/event.hpp"
+#include "engine/time/timestep.h"
+
 #include "engine/export.h"
 
 namespace Core {
@@ -11,7 +13,7 @@ namespace Core {
         virtual ~IApplication() = default;
 
         virtual void OnInit(std::shared_ptr<Scene> scene) {};
-        virtual void OnUpdate() {};
+        virtual void OnUpdate(Timestep dt) {};
         virtual void OnShutdown() {};
         
         virtual void OnEvent(const Event& event) {};

engine/include/engine/renderer/core.h

@@ -30,6 +30,7 @@ private:
     std::shared_ptr<Window> m_window;
     std::unique_ptr<Renderer> m_renderer;
     std::shared_ptr<Scene> m_scene;
+    uint64_t m_elapsed;
     bool m_running;
 };
 

engine/include/engine/time/timestep.h

@@ -0,0 +1,22 @@
+#ifndef TIME_TIMESTEP_H_
+#define TIME_TIMESTEP_H_
+
+namespace Core {
+    class Timestep {
+    public:
+        Timestep(float time = 0.0f)
+            : m_time(time) {}
+
+        [[nodiscard]] float GetSeconds() const { return m_time; }
+        [[nodiscard]] float GetMilliseconds() const { return m_time * 1000.f; }
+
+        operator float() const { return m_time; }
+    public:
+        static Timestep FromMilliseconds(float milliseconds) { return Timestep(milliseconds * 0.001f); }
+        static Timestep FromSeconds(float seconds) { return Timestep(seconds); }
+    private:
+        float m_time;
+    };
+}
+
+#endif // TIME_TIMESTEP_H_

engine/src/renderer/core.cpp

@@ -5,6 +5,8 @@
 #include "engine/window/event.hpp"
 #include "engine/renderer/wavefront.h"
 
+#include "engine/time/timestep.h"
+
 namespace Core {
 
 Engine* Engine::s_instance = nullptr;
@@ -21,10 +23,18 @@ void Engine::Run(std::unique_ptr<IApplication> app) {
 
     m_window->Subscribe(this);
 
+    uint64_t now = SDL_GetPerformanceCounter();
+    m_elapsed = 0;
+
     while (m_running) {
+        m_elapsed = now;
+        now = SDL_GetPerformanceCounter();
+
+        auto dt = Timestep::FromMilliseconds((float)((now - m_elapsed)*1000 / (float)SDL_GetPerformanceFrequency()));
+
         m_window->ProcessEvents();
 
-        m_app->OnUpdate();
+        m_app->OnUpdate(dt);
 
         m_renderer->Render();
 

sandbox/src/main.cpp

@@ -83,24 +83,14 @@ public:
         std::cout << "Game initialized" << std::endl;
 
         m_angle = 3.45f;
-        m_lastTicks = SDL_GetTicks();
 
         m_paused = false;
 
         m_yaw   = -90.0f; // looking along -Z initially
         m_pitch = 0.0f;   // no vertical tilt
-
-        // FPS tracking
-        m_startTicks = SDL_GetTicks();
-        m_frameCount = 0;
     }
 
-    void OnUpdate() override {
+    void OnUpdate(Timestep dt) override {
-        m_currentTicks = SDL_GetTicks();
-        float deltaTime = static_cast<float>(m_currentTicks - m_lastTicks) / 1000.0f; // seconds
-
-        m_lastTicks = m_currentTicks;
-
         float mouseXRel, mouseYRel;
         SDL_GetRelativeMouseState(&mouseXRel, &mouseYRel);
 
@@ -137,19 +127,19 @@ public:
         if (state[SDL_SCANCODE_LSHIFT]) velocity.y -= 1.f;
 
         auto& camTransform = cameraEntity.GetComponent<transform>();
-        camTransform.position += velocity * deltaTime * 2.5f; // speed is e.g. 2.5f
+        camTransform.position += velocity * (float)dt * 2.5f; // speed is e.g. 2.5f
         camTransform.rotation = cameraViewDirection;
 
         // update rotation
         if (!m_paused) {
-            m_angle += glm::radians(45.0f) * deltaTime; // 72° per second
+            m_angle += glm::radians(45.0f) * dt; // 72° per second
             if (m_angle > glm::two_pi<float>()) {
                 m_angle -= glm::two_pi<float>(); // keep value small
             }
         }
 
         // ---- Day-night simulation ----
-        m_dayTime += deltaTime;
+        m_dayTime += dt;
         if (m_dayTime > m_dayLength)
             m_dayTime -= m_dayLength; // loop every "day"
 
@@ -181,23 +171,12 @@ public:
             l.intensity = intensity;
         }
 
-        // auto rotateEntts = m_scene->m_registry.view<transform, rotate>();
+        m_elapsed += dt.GetMilliseconds();
-        // for (auto [entity, t] : rotateEntts.each()) {
-        //     // auto targetTransform = rotateEntts.get<transform>(entity);
-        //     if (!m_scene->m_registry.all_of<light>(entity)) {
-        //         t.rotation.y = m_angle;
-        //     }
-        // }
 
-        m_frameCount++;
+        if (m_elapsed >= 1000) { // one second passed
-        m_currentTicks = SDL_GetTicks();
+            m_elapsed = 0;
-        Uint64 elapsed = m_currentTicks - m_startTicks;
+            double fps = 1 / dt;
-
-        if (elapsed >= 1000) { // one second passed
-            double fps = static_cast<double>(m_frameCount) / (static_cast<double>(elapsed) / 1000.0);
             std::cout << "FPS: " << fps << std::endl;
-            m_frameCount = 0;
-            m_startTicks = m_currentTicks;
         }
     }
 
@@ -211,6 +190,8 @@ public:
         }
     }
 private:
+    int m_elapsed;
+
     std::shared_ptr<Scene> m_scene;
 
     Entity lightEntity;
@@ -218,7 +199,6 @@ private:
     Entity modelEntity;
 
     float m_angle;
-    Uint64 m_lastTicks;
 
     float m_dayTime = 0.0f;       // accumulates time for day-night cycle
     float m_dayLength = 60.0f;    // seconds per full day cycle
@@ -227,12 +207,6 @@ private:
 
     float m_yaw   = -90.0f; // looking along -Z initially
     float m_pitch = 0.0f;   // no vertical tilt
-
-    // FPS tracking
-    Uint64 m_startTicks;
-    int m_frameCount;
-
-    Uint64 m_currentTicks;
 };
 
 IApplication* CreateApplication() {