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@Roland09
Last active January 30, 2020 20:17
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Sprite dynamics using Vector calculation. Example where everything attracts everything, as described in the excellent book The Nature of Code by Daniel Shiffman
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javafx.animation.AnimationTimer;
import javafx.application.Application;
import javafx.geometry.Point2D;
import javafx.scene.Scene;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.Pane;
import javafx.stage.Stage;
public class Main extends Application {
static Random random = new Random();
Pane playfield;
List<Mover> allMovers = new ArrayList<>();
AnimationTimer gameLoop;
Scene scene;
@Override
public void start(Stage primaryStage) {
// create containers
BorderPane root = new BorderPane();
// playfield for our sprites
playfield = new Pane();
playfield.setPrefSize(Settings.SCENE_WIDTH, Settings.SCENE_HEIGHT);
// entire game as layers
Pane layerPane = new Pane();
layerPane.getChildren().addAll(playfield);
root.setCenter(layerPane);
scene = new Scene(root, Settings.SCENE_WIDTH, Settings.SCENE_HEIGHT);
primaryStage.setScene(scene);
primaryStage.show();
// add content
prepareGame();
// run animation loop
startGame();
}
private void prepareGame() {
// add sprites
for (int i = 0; i < Settings.MOVER_COUNT; i++) {
addMovers();
}
}
private void startGame() {
// start game
gameLoop = new AnimationTimer() {
@Override
public void handle(long now) {
// force: attraction
for (Mover m1 : allMovers) {
for (Mover m2 : allMovers) {
if (m1 == m2)
continue;
// calculate attraction
Point2D force = m1.attract(m2);
// apply attraction
m2.applyForce(force);
};
};
// move
allMovers.forEach(Mover::move);
// update in fx scene
allMovers.forEach(Mover::display);
}
};
gameLoop.start();
}
private void addMovers() {
// random location
double x = random.nextDouble() * playfield.getWidth();
double y = random.nextDouble() * playfield.getHeight();
// create sprite data
Point2D location = new Point2D(x, y);
Point2D velocity = new Point2D(0, 0);
Point2D acceleration = new Point2D(0, 0);
double mass = random.nextDouble() * 10 + 10;
// create sprite and add to layer
Mover mover = new Mover(location, velocity, acceleration, mass);
// register sprite
allMovers.add(mover);
// add this node to layer
playfield.getChildren().add(mover);
}
public static void main(String[] args) {
launch(args);
}
}
import javafx.geometry.Point2D;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
public class Mover extends Circle {
Point2D location;
Point2D velocity;
Point2D acceleration;
double mass;
double maxSpeed = Settings.MOVER_MAX_SPEED;
public Mover(Point2D location, Point2D velocity, Point2D acceleration, double mass) {
this.location = location;
this.velocity = velocity;
this.acceleration = acceleration;
this.mass = mass;
// initialize view depending on mass
setRadius( mass);
// create view
setStroke(Color.BLUE);
setFill(Color.BLUE.deriveColor(1, 1, 1, 0.3));
}
public void applyForce(Point2D force) {
Point2D f = new Point2D( force.getX(), force.getY());
f = f.multiply(1/mass);
acceleration = acceleration.add(f);
}
public void move() {
// set velocity depending on acceleration
velocity = velocity.add(acceleration);
// limit velocity to max speed
double mag = velocity.magnitude();
if( mag > Settings.MOVER_MAX_SPEED) {
velocity = velocity.normalize();
velocity = velocity.multiply(mag);
}
// change location depending on velocity
location = location.add(velocity);
// clear acceleration
acceleration = new Point2D(0,0);
}
public Point2D attract(Mover m) {
// force direction
Point2D force = location.subtract(m.location);
double distance = force.magnitude();
// constrain movement
distance = constrain(distance, Settings.ATTRACTION_DISTANCE_MIN, Settings.ATTRACTION_DISTANCE_MAX);
force = force.normalize();
// force magnitude
double strength = (Settings.GRAVITATIONAL_CONSTANT * mass * m.mass) / (distance * distance);
force = force.multiply(strength);
return force;
}
public static double constrain(double value, double min, double max) {
if (value < min)
return min;
if (value > max)
return max;
return value;
}
public void display() {
setCenterX( location.getX());
setCenterY( location.getY());
}
}
public class Settings {
public static double SCENE_WIDTH = 1280;
public static double SCENE_HEIGHT = 720;
public static int MOVER_COUNT = 500;
public static double MOVER_MAX_SPEED = 20;
// ensure that attraction is applied with at least min and max
// we don't want it to be too weak or too strong
public static double ATTRACTION_DISTANCE_MIN = 5;
public static double ATTRACTION_DISTANCE_MAX = 25.0;
// Univeral Gravitational Constant; real world: 6.67428E10-11;
public static double GRAVITATIONAL_CONSTANT = 0.004;
}
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