added new sample code to demonstrate mass

fxgl-core/src/main/java/module-info.java

@@ -58,6 +58,7 @@
     exports com.almasb.fxgl.pathfinding.heuristic;
     exports com.almasb.fxgl.pathfinding.maze;
     exports com.almasb.fxgl.physics;
+    exports com.almasb.fxgl.physics.box2d.collision.shapes;
     exports com.almasb.fxgl.physics.box2d.dynamics;
     exports com.almasb.fxgl.physics.box2d.dynamics.joints;
     exports com.almasb.fxgl.procedural;

fxgl-samples/src/main/java/basics/MassSample.java

@@ -0,0 +1,213 @@
+/*
+ * FXGL - JavaFX Game Library. The MIT License (MIT).
+ * Copyright (c) AlmasB (almaslvl@gmail.com).
+ * See LICENSE for details.
+ */
+
+
+package basics;
+
+
+import com.almasb.fxgl.app.GameApplication;
+import com.almasb.fxgl.app.GameSettings;
+import com.almasb.fxgl.dsl.FXGL;
+import com.almasb.fxgl.entity.Entity;
+import com.almasb.fxgl.input.UserAction;
+import com.almasb.fxgl.physics.BoundingShape;
+import com.almasb.fxgl.physics.HitBox;
+import com.almasb.fxgl.physics.PhysicsComponent;
+import com.almasb.fxgl.physics.box2d.collision.shapes.MassData;
+import com.almasb.fxgl.physics.box2d.dynamics.BodyType;
+import com.almasb.fxgl.physics.box2d.dynamics.FixtureDef;
+import javafx.geometry.Point2D;
+import javafx.scene.input.KeyCode;
+import javafx.scene.input.MouseButton;
+import javafx.scene.paint.Color;
+import javafx.scene.shape.Circle;
+import javafx.scene.shape.Rectangle;
+import javafx.scene.text.Font;
+import javafx.scene.text.Text;
+
+
+import static com.almasb.fxgl.dsl.FXGL.*;
+
+
+/**
+ * Shows how to change mass within a body directly
+ * and the affect this has on general physics.
+ *
+ * demonstrated using a seesaw, you can see
+ * how objects of different masses interact with
+ * their environment differently.
+ *
+ * @author Issy Kelly @IssyKelly
+ */
+public class MassSample extends GameApplication {
+
+
+    int mass = 1;
+    Text uiText;
+
+
+    @Override
+    protected void initSettings(GameSettings settings) {
+        settings.setWidth(1280);
+        settings.setHeight(720);
+    }
+
+
+    @Override
+    protected void initInput() {
+        // click to add a new ball of the shown (on screen) mass
+        getInput().addAction(new UserAction("LMB") {
+            private double x;
+            private double y;
+
+
+            @Override
+            protected void onActionBegin() {
+                x = getInput().getMouseXWorld();
+                y = getInput().getMouseYWorld();
+                newBall(mass, x, y);
+            }
+        }, MouseButton.PRIMARY);
+
+
+        // press E to increase the mass of new balls by 1
+        onKeyDown(KeyCode.E, () -> {
+            mass += 1;
+            uiText.setText(mass + " mass");
+        });
+
+
+        // press P to increase the mass of new balls by 10
+        onKeyDown(KeyCode.P, () -> {
+            mass += 10;
+            uiText.setText(mass + " mass");
+        });
+
+
+        // press Q to decrease the mass of new balls by 1
+        onKeyDown(KeyCode.Q, () -> {
+            mass -= 1;
+            uiText.setText(mass + " mass");
+        });
+
+
+        // press O to decrease the mass of new balls by 10
+        onKeyDown(KeyCode.O, () -> {
+            mass -= 10;
+            uiText.setText(mass + " mass");
+        });
+    }
+
+
+    @Override
+    protected void initGame() {
+        getGameScene().setBackgroundColor(Color.LIGHTGRAY);
+
+
+        uiText = new Text(mass + " mass");
+        Font uifont = new Font(40);
+        uiText.setFont(uifont);
+        FXGL.addUINode(uiText, 600, 100);
+
+
+
+
+        //floor
+        Entity floor = entityBuilder()
+                .at(0, 700)
+                .viewWithBBox(new Rectangle(1450, 10, Color.BLACK))
+                .with(new PhysicsComponent())
+                .buildAndAttach();
+
+
+        // balls for right hand seesaw
+        newBall(100, 1050, 300);
+        newBall(10, 700,300);
+
+
+        // balls for left hand side seesaw
+        newBall(20, 170, 300);
+        newBall(10, 300,300);
+
+
+        newSeesaw(250,600, 1);
+        newSeesaw(900,550, 1.4);
+    }
+
+
+    public void newSeesaw(int x, int y, double size){
+        int circum = (int) (10 * size);
+        int rectx = (int) (400 * size);
+
+
+        Entity circle = entityBuilder()
+                .at(x, y)
+                .viewWithBBox(new Circle(circum, Color.BLACK))
+                .with(new PhysicsComponent())
+                .buildAndAttach();
+
+
+        circle.getComponent(PhysicsComponent.class)
+                .setBodyType(BodyType.STATIC);
+
+
+        PhysicsComponent plankPhysics = new PhysicsComponent();
+        plankPhysics.setBodyType(BodyType.DYNAMIC);
+        FixtureDef fd = new FixtureDef();
+        fd.setDensity(5.0f);
+        plankPhysics.setFixtureDef(fd);
+
+
+        Entity plank = entityBuilder()
+                .at(x, y)
+                .viewWithBBox(new Rectangle(rectx, 20, Color.BROWN))
+                .with(plankPhysics)
+                .buildAndAttach();
+
+
+        Point2D anchor = new Point2D((circum/2), (circum/2));
+        Point2D anchor2 = new Point2D((rectx/2), (20/2));
+
+
+        getPhysicsWorld().addRevoluteJoint(
+                circle,
+                plank,
+                anchor,
+                anchor2
+        );
+    }
+
+
+    public void newBall(int mass, double x, double y){
+        var physics = new PhysicsComponent();
+        physics.setFixtureDef(new FixtureDef().density(25.5f).restitution(0.5f));
+        physics.setBodyType(BodyType.DYNAMIC);
+
+
+        MassData massValue = new MassData();
+        // the code to directly change the mass of a body
+        massValue.mass = mass;
+        physics.setOnPhysicsInitialized(() -> physics.getBody().setMassData(massValue));
+
+
+        entityBuilder()
+                .at(x, y)
+                .bbox(new HitBox(BoundingShape.circle(450 / 15.0 / 2.0)))
+                .view(texture("ball.png", 450 / 15.0, 449 / 15.0).multiplyColor(Color.BLUE))
+                .with(physics)
+                .buildAndAttach();
+    }
+
+
+    static void main(String[] args) {
+        launch(args);
+    }
+}
+
+
+
+
+