Merge pull request #18 from SHADE-DP/SP3-19-frame-rate-controller

FRC implemented
Handles the main game loop, which includes:

Handling restarting of scenes by freeing and initializing again
Handling changes of scenes by unloading previous scene and loading the next
Calling to update on a fixed time basis and reducing the accumulator
Calling to render on a variable time basis and adding to the accumulator
Measuring of variable time elapsed per frame
Ready for integration. Anticipating much change from this implementation during integration.

SHADE_Engine/SHADE_Engine.vcxproj

@@ -123,6 +123,7 @@
     <ClInclude Include="src\ECS_Base\System\SHSystemManager.h" />
     <ClInclude Include="src\Engine\SHEngine.h" />
     <ClInclude Include="src\Filesystem\SHFileSystem.h" />
+    <ClInclude Include="src\FRC\SHFramerateController.h" />
     <ClInclude Include="src\Graphics\Buffers\SHVkBuffer.h" />
     <ClInclude Include="src\Graphics\Commands\SHCommandPoolResetMode.h" />
     <ClInclude Include="src\Graphics\Commands\SHVkCommandBuffer.h" />
@@ -210,6 +211,7 @@
     <ClCompile Include="src\ECS_Base\System\SHSystemManager.cpp" />
     <ClCompile Include="src\Engine\SHEngine.cpp" />
     <ClCompile Include="src\Filesystem\SHFileSystem.cpp" />
+    <ClCompile Include="src\FRC\SHFramerateController.cpp" />
     <ClCompile Include="src\Graphics\Buffers\SHVkBuffer.cpp" />
     <ClCompile Include="src\Graphics\Commands\SHVkCommandBuffer.cpp" />
     <ClCompile Include="src\Graphics\Commands\SHVkCommandPool.cpp" />

SHADE_Engine/SHADE_Engine.vcxproj.filters

@@ -387,6 +387,7 @@
     <ClInclude Include="src\Tools\SHUtilities.h">
       <Filter>Tools</Filter>
     </ClInclude>
+    <ClInclude Include="src\FRC\SHFramerateController.h" />
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="src\ECS_Base\Components\SHComponent.cpp">
@@ -591,5 +592,6 @@
     <ClCompile Include="src\Tools\SHLogger.cpp">
       <Filter>Tools</Filter>
     </ClCompile>
+    <ClCompile Include="src\FRC\SHFramerateController.cpp" />
   </ItemGroup>
 </Project>

SHADE_Engine/src/FRC/SHFramerateController.cpp

@@ -0,0 +1,134 @@
+/*********************************************************************
+ * \file   SHFramerateController.cpp
+ * \author Ryan Wang Nian Jing
+ * \brief  Definition for functions of the framerate controller
+ *				 Handles changing of scenes and manages loop (timestep, etc.)
+ *
+ * \copyright Copyright (c) 2022 DigiPen Institute of Technology. Reproduction
+	 or disclosure of this file or its contents without the prior written
+	 consent of DigiPen Institute of Technology is prohibited.
+ *********************************************************************/
+
+#include <chrono>
+#include <cassert>
+#include <SHpch.h>
+#include "SHFramerateController.h"
+#include "../Tools/SHLogger.h"
+
+namespace SHADE
+{
+	//Init statics
+	double SHFramerateController::fixedTimestep = 0.01;
+	SHScene* SHFramerateController::previousScene = nullptr;
+	SHScene* SHFramerateController::currentScene = nullptr;
+	SHScene* SHFramerateController::nextScene = nullptr;
+	bool SHFramerateController::toRestart = false;
+	bool SHFramerateController::toQuit = false;
+
+	//Scene manager loop
+	void SHFramerateController::Run(SHScene* firstScene)
+	{
+		if (firstScene == nullptr)
+		{
+			SHLOG_ERROR("Do not pass a nullptr as the firstScene");
+			return;
+		}
+
+		//Set quit and restart flags to false
+		toQuit = false;
+		toRestart = false;
+
+		//Set the first scene to run
+		previousScene = firstScene;
+		currentScene = firstScene;
+		nextScene = firstScene;
+
+		while (!toQuit)
+		{
+			if (toRestart)
+			{
+				//Restart current scene
+				currentScene = previousScene;
+				nextScene = previousScene;
+				toRestart = false;
+			}
+			else
+			{
+				//Move to a new scene
+				currentScene->Load();
+			}
+
+			//Call init function of current scene
+			currentScene->Init();
+
+			//Have an initial value
+			//This frame time will fluctuate
+			//SHOULD be larger than the fixed timestep
+			//TODO this might need to be changed
+			double variableLastFrameTime = fixedTimestep;
+
+			//Time accumulator for meshing between fixed and variable timesteps
+			double accumulator = 0.0;
+
+			//Start state loop
+			while (currentScene == nextScene && !toQuit && !toRestart)
+			{
+				//Use of new STL timing functions
+				//https://en.cppreference.com/w/cpp/chrono
+				std::chrono::duration<double> deltaTime;
+
+				auto startTime = std::chrono::high_resolution_clock::now();
+
+				//Whittle down the accumulator by continuously simulating
+				for (; accumulator > fixedTimestep; accumulator -= fixedTimestep)
+				{
+					MSG msg;
+					if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
+					{
+						TranslateMessage(&msg);
+						DispatchMessage(&msg);
+					}
+
+					//TODO change to double
+					currentScene->Update((float)fixedTimestep);
+				}
+
+				//Interpolation
+				//Manage the alpha value well
+				//https://randomascii.wordpress.com/2012/02/13/dont-store-that-in-a-float/
+				//Key points:
+				//1) Any time you add or subtract floats of widely varying
+				//   magnitudes, you need to watch for loss of precision
+				//2) Sometimes using double instead of float is the correct
+				//   solution, but often a more stable algorithm is more important
+				//3) calcT() should probably use double (to give sufficient
+				//   precision after many hours of gameplay)
+
+				//TODO awaiting approval to use this
+				//double alpha = accumulator / fixedTimestep;
+
+				//assert alpha does not go out of range
+
+				currentScene->Render();
+
+				auto endTime = std::chrono::high_resolution_clock::now();
+				deltaTime = endTime - startTime;
+				variableLastFrameTime = deltaTime.count();
+
+				//Increase accumulator
+				accumulator += variableLastFrameTime;
+			}
+
+			//Free once out of scene loop
+			currentScene->Free();
+
+			//Check if not to restart state
+			//If so, unload
+			if (!toRestart) currentScene->Unload();
+
+			//Shift forward scenes
+			previousScene = currentScene;
+			currentScene = nextScene;
+		}
+	}
+}

SHADE_Engine/src/FRC/SHFramerateController.h

@@ -0,0 +1,62 @@
+/*********************************************************************
+ * \file   SHFramerateController.h
+ * \author Ryan Wang Nian Jing
+ * \brief  Declaration for the framerate controller
+ *				 Handles changing of scenes and manages loop (timestep, etc.)
+ *
+ * \copyright Copyright (c) 2022 DigiPen Institute of Technology. Reproduction
+	 or disclosure of this file or its contents without the prior written
+	 consent of DigiPen Institute of Technology is prohibited.
+ *********************************************************************/
+
+#ifndef SH_FRAMERATECONTROLLER_H
+#define SH_FRAMERATECONTROLLER_H
+#pragma once
+
+#include "../Scene/SHScene.h"
+
+namespace SHADE
+{
+	class SHFramerateController
+	{
+	private:
+		//scene pointers
+		static SHScene* previousScene;
+		static SHScene* currentScene;
+		static SHScene* nextScene;
+
+		//Flags
+		//Whether the flag has been raised for the game to be quit
+		static bool toQuit;
+
+		//Whether the flag has been raised for the current scene to restart
+		static bool toRestart;
+
+	public:
+		//Fixed timestep value for physics. Default at 1/100th of a second.
+		//Should be lower than the variable refresh rate
+		static double fixedTimestep;
+
+		//Scene Manager Loop
+		//This loop is vital to the game because it runs for as long as the game
+		//runs. Before entering, initialise vital systems for game. After exiting,
+		//free these vital systems before finishing the main() function and
+		//terminating the game
+		//Parameter of firstScene is what scene the game should start with
+		static void Run(SHScene* firstScene);
+
+		//Set the flag to restart the current game scene
+		static inline void RestartScene() { toRestart = true; }
+
+		//Set the flag to halt running of the scene manager and quit the game
+		static inline void QuitGame() { toQuit = true; }
+
+		//Set the next scene to be excuted
+		//This will tell the scene manager to
+		//halt execution of the current scene and prepare
+		//execution of the next
+		static inline void SetNextScene(SHScene* const next) { nextScene = next; }
+	};
+}
+
+#endif