Fully implemented the ECS

Basic example implementation also included, with a single entity that is under the effect of gravity. Various debug systems included

javaecs/src/main/java/nz/ac/massey/programming_project_159333_s1_2021/App.java

@@ -1,5 +1,7 @@
 package nz.ac.massey.programming_project_159333_s1_2021;
 
+import java.util.BitSet;
+
 /**
  * Hello world!
  */
@@ -10,8 +12,76 @@ public final class App {
     /**
      * Says hello to the world.
      * @param args The arguments of the program.
+     * @throws InterruptedException
      */
-    public static void main(String[] args) {
+    public static void main(String[] args) throws InterruptedException {
+        ECS gameEngine = new ECS();
         System.out.println("Hello World!");
+        gameEngine.registerComponent(Vec2D.class.getName());
+        gameEngine.registerComponent(RidgidBody.class.getName());
+        gameEngine.registerComponent(Gravity.class.getName());
+
+        PhysicsSystem physicsSystem = new PhysicsSystem(gameEngine);
+        gameEngine.registerSystem(PhysicsSystem.class.getName(), physicsSystem);
+        {
+            BitSet signature = new BitSet();
+            signature.set(gameEngine.getComponentIndex(Gravity.class.getName()));
+            signature.set(gameEngine.getComponentIndex(Vec2D.class.getName()));
+            signature.set(gameEngine.getComponentIndex(RidgidBody.class.getName()));
+            gameEngine.setSystemSignature(PhysicsSystem.class.getName(), signature);
+        }
+
+        physicsSystem.init();
+
+        LogVec2DSystem logVec2DSystem = new LogVec2DSystem(gameEngine);
+        gameEngine.registerSystem(LogVec2DSystem.class.getName(), logVec2DSystem);
+        {
+            BitSet signature = new BitSet();
+            signature.set(gameEngine.getComponentIndex(Gravity.class.getName()));
+            signature.set(gameEngine.getComponentIndex(Vec2D.class.getName()));
+            signature.set(gameEngine.getComponentIndex(RidgidBody.class.getName()));
+            gameEngine.setSystemSignature(LogVec2DSystem.class.getName(), signature);
+        }
+
+        logVec2DSystem.init();
+
+        FrameRateSystem frameRateSystem = new FrameRateSystem();
+        gameEngine.registerSystem(FrameRateSystem.class.getName(), frameRateSystem);
+
+        // Create components:
+
+        int entity = gameEngine.createEntity();
+
+        gameEngine.addComponent(entity, Gravity.class.getName(), new Gravity(0.0, -9.80665, -1.0, 100.0));
+        gameEngine.addComponent(entity, Vec2D.class.getName(), new Vec2D(1.5, 0.0, 1));
+        gameEngine.addComponent(entity, RidgidBody.class.getName(), new RidgidBody());
+
+
+        
+        double dt = 0.0;
+
+        double frameRate = 1.0 / 20; // 1 second divided by target number of frames
+
+        boolean quit = false;
+        long loopStart = System.currentTimeMillis();
+        while (!quit){
+            // Get the time between frames for accurate time-based calculations (i.e. physics systems etc)
+            long startTime = System.nanoTime();
+
+            frameRateSystem.update(dt);
+            physicsSystem.update(dt);
+            logVec2DSystem.update(dt);
+            dt = (System.nanoTime() - startTime) / 1e9; // convert nanoseconds to seconds
+
+            // Limit frame rate (approximately) to minimum of 16 ms
+            if (dt < frameRate){
+                Thread.sleep((int)((frameRate-dt)*1000));
+                dt = (System.nanoTime() - startTime) / 1e9;
+            }
+            if (System.currentTimeMillis() - loopStart >= 1000){
+                loopStart = System.currentTimeMillis();
+                System.out.println("Second Elapsed");
+            }
+        }
     }
 }

javaecs/src/main/java/nz/ac/massey/programming_project_159333_s1_2021/ComponentArray.java

@@ -1,4 +1,23 @@
-import java.util.*;
+package nz.ac.massey.programming_project_159333_s1_2021;
+/**
+ * Component Array
+ * Defines the data structure that component data is stored under.
+ * Has a list of defined objects, and two associative maps that link
+ * the position of the data with the entity number.
+ * 
+ * Therefore, every entity in entityComponentDataMap is valid, so
+ * no additional sorting is required
+ * 
+ * 
+ * Contributors:
+ * Brychan Dempsey - brychand@hotmail.com
+ * 
+ */
+
+import java.util.Map;
+import java.util.HashMap;
+import java.util.List;
+import java.util.ArrayList;
 
 
 class ComponentArray{
@@ -8,8 +27,7 @@ class ComponentArray{
     Map<Integer, Integer> componentDataEntityMap = new HashMap<>();
 
     public void entityDestroyed(int entity){
-        Optional<Integer> pos = entityComponentDataMap.get(entity);
+        if (entityComponentDataMap.containsKey(entity)){
-        if (pos.isEmpty()){
             removeData(entity);
         }
     }
@@ -36,8 +54,7 @@ class ComponentArray{
     }
 
     public void insertData(int entity, Object component){
-        Optional<Integer> pos = entityComponentDataMap.get(entity);
+        if (entityComponentDataMap.containsKey(entity)){
-        if (!pos.isEmpty()){
             System.err.println("Entity is already subscribed to the component");
             return;
         }

javaecs/src/main/java/nz/ac/massey/programming_project_159333_s1_2021/ComponentManager.java

@@ -1,5 +1,15 @@
-import java.util.BitSet;
+package nz.ac.massey.programming_project_159333_s1_2021;
+/**
+ * Component Manager
+ * This class manages component registrations, and adding,
+ * removing, and retrieving data from the component arrays.
+ * 
+ * Contributors:
+ * Brychan Dempsey - brychand@hotmail.com
+ * 
+ */
 import java.util.Map;
+import java.util.HashMap;
 
 class ComponentManager{
     Map<String, ComponentArray> componentArrays = new HashMap<>();

javaecs/src/main/java/nz/ac/massey/programming_project_159333_s1_2021/ECS.java

@@ -1,58 +1,127 @@
+package nz.ac.massey.programming_project_159333_s1_2021;
 /**
- * ECS root file
+ * ECS manager class.
+ * Call this class and its functions to interact correctly with the ECS system.
  * 
  * Contributors:
  * Brychan Dempsey - brychand@hotmail.com
  * 
  * References:
+ * Based on the implementation by Austin Morlan:
  * https://code.austinmorlan.com/austin/ecs - 'A simple C++ Entity Component System' - released under MIT licence
  *  
  */
 
-import java.util.*;
+import java.util.BitSet;
-
+/**
+ * The ECS manager.
+ * <p>
+ * See <href src="https://git.software.kauripeak.co.nz/BrychanD/JavaECS">https://git.software.kauripeak.co.nz/BrychanD/JavaECS</href>
+ * for documentation and more information.
+ */
 public class ECS {
-    EntityManager entityManager;
+    protected EntityManager entityManager;
-    ComponentManager componentManager;
+    protected ComponentManager componentManager;
-    SystemManager systemManager;
+    protected SystemManager systemManager;
-
+    /**
+     * Initialises the ECS with default values
+     * <p>
+     * Maximum 1024 enitites default
+     */
     public ECS(){
         entityManager = new EntityManager();
         componentManager = new ComponentManager();
         systemManager = new SystemManager();
     }
 
+    /**
+     * Initialises the ECS with the specified value(s)
+     * @param maxEntities the maximum number of entities to allow
+     */
+    public ECS(int maxEntities){
+        entityManager = new EntityManager(maxEntities);
+        componentManager = new ComponentManager();
+        systemManager = new SystemManager();
+    }
 
+    /**
+     * Creates a new entity
+     * @return the id of the new entity
+     */
     Integer createEntity(){
         return entityManager.addEntity();
     }
 
+    /**
+     * Signals each manager to remove the specified entity
+     * @param entity the entity to destroy
+     */
     void destroyEntity(int entity){
         entityManager.removeEntity(entity);
         componentManager.entityDestroyed(entity);
         systemManager.entityDestroyed(entity);
     }
 
+    /**
+     * Registers the specified name in the component manager
+     * @param name the name to register. Should be the component class name or a suitable name for primitive types
+     */
     void registerComponent(String name){
         componentManager.registerComponent(name);
     }
 
+    Integer getComponentIndex(String name){
+        return componentManager.getComponentIndex(name);
+    }
+
+    /**
+     * Adds an exisiting component to an exisiting entity
+     * @param entity the entity to add the component to
+     * @param componentName the class name of the component to add
+     * @param component the actual component data
+     */
     void addComponent(int entity, String componentName, Object component){
         componentManager.addComponentToEntity(componentName, component, entity);
         entityManager.registerComponent(componentManager.getComponentIndex(componentName), entity);
         systemManager.entitySignatureChanged(entity, entityManager.getRegistrations(entity));
     }
 
+    /**
+     * Removes the component from the specified entity
+     * @param entity the entity to remove the component from
+     * @param componentName the class name of the component
+     */
     void removeComponent(int entity, String componentName){
         componentManager.removeComponentFromEntity(componentName, entity);
         entityManager.unregisterComponent(componentManager.getComponentIndex(componentName), entity);
         systemManager.entitySignatureChanged(entity, entityManager.getRegistrations(entity));
     }
 
+    /**
+     * Gets the actual data of the component associated to the entity.
+     * May require casting from Object to the known data type
+     * @param entity the entity to retrieve the data for
+     * @param componentName the class name of the component
+     * @return the component data Object associated with the entity
+     */
     Object getComponentData(int entity, String componentName){
-        return componentManager.getComponentData(entity, componentName);
+        return componentManager.getComponent(componentName, entity);
     }
 
+    /**
+     * 
+     * @param systemName
+     * @param action
+     */
+    void registerSystem(String systemName, ECSSystem action){
+        systemManager.registerSystem(systemName, action);
+    }
+
+    /**
+     * Sets the specified system's signature to the provided signature
+     * @param system the class name of the system to set the signature of
+     * @param signature the new signature data
+     */
     void setSystemSignature(String system, BitSet signature){
         systemManager.setSignature(system, signature);
     }

javaecs/src/main/java/nz/ac/massey/programming_project_159333_s1_2021/ECSSystem.java

@@ -1,4 +1,19 @@
+package nz.ac.massey.programming_project_159333_s1_2021;
+/**
+ * ECS System class
+ * This class stores entity-system registrations. These are
+ * updated by SystemManager, but need a type to store the
+ * data under.
+ * 
+ * All systems should inherit from this
+ * 
+ * Contributors:
+ * Brychan Dempsey - brychand@hotmail.com
+ * 
+ */
+
 import java.util.Set;
+import java.util.HashSet;
 
 class ECSSystem{
     Set<Integer> entities = new HashSet<>();

javaecs/src/main/java/nz/ac/massey/programming_project_159333_s1_2021/EntityManager.java

@@ -1,8 +1,21 @@
+package nz.ac.massey.programming_project_159333_s1_2021;
+/**
+ * Entity Manager
+ * This class manages entity allocations; keeping a list
+ * of all unassigned entities values. 
+ * Additionally, handles setting the registered component
+ * flags for an entity.
+ * 
+ * Contributors:
+ * Brychan Dempsey - brychand@hotmail.com
+ * 
+ */
+
 import java.util.BitSet;
+import java.util.LinkedList;
 import java.util.List;
 import java.util.Queue;
-
+import java.util.ArrayList;
-import javax.swing.text.html.parser.Entity;
 
 // Define the manager classes internally - should be moved to seperate source files as appropriate
 /**
@@ -15,7 +28,7 @@ class EntityManager{
     List<BitSet> entityRegistrations;
 
     public EntityManager(){
-        unusedEntities = new ArrayList<>();
+        unusedEntities = new LinkedList<>();
         entityRegistrations = new ArrayList<>();
 
         for (int i = 0; i < 1024; i++) {
@@ -25,7 +38,7 @@ class EntityManager{
     }
 
     public EntityManager(int maxEntities){
-        unusedEntities = new ArrayList<>();
+        unusedEntities = new LinkedList<>();
         entityRegistrations = new ArrayList<>();
         
         for (int i = 0; i < maxEntities; i++) {

javaecs/src/main/java/nz/ac/massey/programming_project_159333_s1_2021/FrameRateSystem.java

@@ -0,0 +1,9 @@
+package nz.ac.massey.programming_project_159333_s1_2021;
+
+public class FrameRateSystem extends ECSSystem{
+    void init() {}
+
+    void update(double dt){
+        System.out.print("dt: " + dt + " ");
+    }
+}

javaecs/src/main/java/nz/ac/massey/programming_project_159333_s1_2021/Gravity.java

@@ -0,0 +1,23 @@
+package nz.ac.massey.programming_project_159333_s1_2021;
+
+public class Gravity {
+    public Gravity(){
+
+    }
+    public Gravity(double x, double y){
+        this.x = x;
+        this.y = y;
+    }
+    public Gravity(double x, double y, double terminalX, double terminalY){
+        this.x = x;
+        this.y = y;
+        this.terminalX = terminalX;
+        this.terminalY = terminalY;
+    }
+    double x = 0.0;
+    double y = -9.80665;
+    // Gravity won't be considered if the velocity exceeds this (absolute value). Negative values are ignored (not limited)
+    double terminalX = -1.0;
+    double terminalY = -1.0;
+    
+}

javaecs/src/main/java/nz/ac/massey/programming_project_159333_s1_2021/LogVec2DSystem.java

@@ -0,0 +1,17 @@
+package nz.ac.massey.programming_project_159333_s1_2021;
+
+public class LogVec2DSystem extends ECSSystem{
+    ECS gameEngine;
+    public LogVec2DSystem(ECS gameEngine){
+        this.gameEngine = gameEngine;
+    }
+
+    void init() {}
+
+    void update(double dt){
+        for (Integer entity : entities) {
+            Vec2D pos = (Vec2D)gameEngine.getComponentData(entity, Vec2D.class.getName());
+            System.out.println("X: " + pos.x + ", Y:" + pos.y);
+        }
+    }
+}

javaecs/src/main/java/nz/ac/massey/programming_project_159333_s1_2021/PhysicsSystem.java

@@ -0,0 +1,33 @@
+package nz.ac.massey.programming_project_159333_s1_2021;
+
+public class PhysicsSystem extends ECSSystem{
+    ECS gameEngine;
+    public PhysicsSystem(ECS gameEngine){
+        this.gameEngine = gameEngine;
+    }
+
+    void init() {}
+
+    void update(double dt){
+        for (Integer entity : entities) {
+            Vec2D pos = (Vec2D)gameEngine.getComponentData(entity, Vec2D.class.getName());
+            RidgidBody ridgidBody = (RidgidBody)gameEngine.getComponentData(entity, RidgidBody.class.getName());
+            Gravity gravity = (Gravity)gameEngine.getComponentData(entity, Gravity.class.getName());
+            // Firstly, add the result of the accelerative forces to the ridgidbody
+            ridgidBody.xdot += ridgidBody.xAcc * dt;
+            ridgidBody.ydot += ridgidBody.yAcc * dt;
+            
+            // Special case of gravity
+            if (gravity.terminalX < 0 || Math.abs(ridgidBody.xdot) < gravity.terminalX){
+                ridgidBody.xdot += gravity.x * dt;
+            }
+            if (gravity.terminalY < 0 || Math.abs(ridgidBody.ydot) < gravity.terminalY){
+                ridgidBody.ydot += gravity.y * dt;
+            }
+            
+            // Finally, move the vec2d by the new velocity
+            pos.x += ridgidBody.xdot * dt;
+            pos.y += ridgidBody.ydot * dt;
+        }
+    }
+}

javaecs/src/main/java/nz/ac/massey/programming_project_159333_s1_2021/RidgidBody.java

@@ -0,0 +1,18 @@
+package nz.ac.massey.programming_project_159333_s1_2021;
+
+public class RidgidBody {
+    public RidgidBody(){}
+    public RidgidBody(double xdot, double ydot, double xAcc, double yAcc){
+        this.xdot = xdot;
+        this.ydot = ydot;
+        this.xAcc = xAcc;
+        this.yAcc = yAcc;
+    }
+
+    // Velocities
+    double xdot = 0.0;
+    double ydot = 0.0;
+    // accelerations
+    double xAcc = 0.0;
+    double yAcc = 0.0;
+}

javaecs/src/main/java/nz/ac/massey/programming_project_159333_s1_2021/SystemManager.java

@@ -1,15 +1,22 @@
+package nz.ac.massey.programming_project_159333_s1_2021;
+/**
+ * System Manager
+ * This class manages systems registrations, and keeps a current list
+ * of all entities the system should operate on
+ * 
+ * Contributors:
+ * Brychan Dempsey - brychand@hotmail.com
+ * 
+ */
+
 import java.util.BitSet;
 import java.util.Map;
+import java.util.HashMap;
 
 class SystemManager{
     Map<String, BitSet> signatures = new HashMap<>();
     Map<String, ECSSystem> systems = new HashMap<>();
 
-
-    public SystemManager(ECS baseECS){
-        this.baseECS = baseECS;
-        systemIndex = 0;
-    }
     // Registering the system adds it to the array of systems.
     // In Austin Morlan's implementation, this also creates an instance of the
     // system that can be called from the main thread.
@@ -25,6 +32,7 @@ class SystemManager{
             return false;
         }
         systems.put(system, action);
+        signatures.put(system, new BitSet());
         return true;
     }
 
@@ -40,11 +48,16 @@ class SystemManager{
 
     public void entitySignatureChanged(int entity, BitSet entitySignature){
         for (String key : systems.keySet()) {
-            if (entitySignature.and(signatures.get(key)) == signatures.get(key)){ // Bitwise check if the entity is subscribed to this system
+            // Check if the signature is null
-                systems.get(key).entities.add(entity);
+            if (!entitySignature.equals(null)){
-            }
+                BitSet srcCpy = (BitSet)entitySignature.clone();
-            else{
+                srcCpy.and(signatures.get(key));
-                systems.get(key).entities.remove(entity);
+                if (srcCpy.equals(signatures.get(key))){ // Bitwise check if the entity is subscribed to this system
+                    systems.get(key).entities.add(entity);
+                }
+                else{
+                    systems.get(key).entities.remove(entity);
+                }
             }
         }
     }

javaecs/src/main/java/nz/ac/massey/programming_project_159333_s1_2021/Vec2D.java

@@ -0,0 +1,13 @@
+package nz.ac.massey.programming_project_159333_s1_2021;
+
+public class Vec2D {
+    public Vec2D(){}
+    public Vec2D(double x, double y, int z){
+        this.x = x;
+        this.y = y;
+        this.z = z;
+    }
+    double x = 0.0;
+    double y = 0.0;
+    int z = 0;
+}