EllipseExp.java

package fjr.ellipse;

import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
import javafx.util.Duration;


// @author moh_fajar 
// @date: 31-1-2014

public class EllipseExp extends Application {

	public static void main(String[] args) {
		launch(args);
	}

	Timeline animation;
	GraphicsContext gc; 
	Canvas canvas; 
	Trammel tr ;
	
	double angle; 

	double canvasWidth = 450 , canvasHeight = 350 ; 
	@Override
	public void start(Stage primaryStage) throws Exception {
		Group root = new Group();
		Group child = new Group(); 
		primaryStage.setScene(new Scene(root,500, 500));
		angle = 45; 
		tr = new Trammel(200, 150 , 100, 60, angle);
		canvas = new Canvas(canvasWidth, canvasHeight); 
		gc = canvas.getGraphicsContext2D(); 
		root.getChildren().add(child); 
		child.getChildren().addAll(canvas);
		animation = new Timeline();
		animation.getKeyFrames().addAll(
				new KeyFrame(Duration.millis(10),
						new EventHandler<ActionEvent>() {
							@Override
							public void handle(ActionEvent arg0) {
								angle-= Math.PI/200 ; 
								tr.setAngle(angle);
								tr.calculatePosition();
								draw(gc);
							}
						}));

		primaryStage.show();
		
		animation.setCycleCount(Timeline.INDEFINITE);
		animation.setAutoReverse(false);
		animation.play(); 
	}
	
	void draw(GraphicsContext gc){
		gc.setFill(Color.WHITE);
		gc.fillRect(0, 0, canvasWidth, canvasHeight);
		gc.setStroke(Color.BLACK);
		gc.strokeRect(0, 0, canvasWidth, canvasHeight);
		gc.setFill(Color.RED);
		gc.fillRect(tr.x, tr.y, 5, 5);
		gc.setFill(Color.BLUE);
		gc.fillRect(tr.x1, tr.y1, 5, 5);
		
		gc.setFill(Color.GREENYELLOW);
		gc.fillRect(tr.x2, tr.y2, 5, 5);
		
		gc.setStroke(Color.RED);
		gc.strokeLine(tr.x, tr.y, tr.x2, tr.y2);
		
		
		gc.setStroke(Color.BLACK);
		gc.strokeLine(tr.x2, tr.y1 - 110 , tr.x2, tr.y1 + 110);
		gc.strokeLine(tr.x2- 200, tr.y1  , tr.x2 + 200, tr.y1 );
		
		gc.setStroke(Color.BLACK);
		gc.strokeOval(tr.getXCorrection() -   tr.getA(), tr.getYCorrection() -  
				  tr.getB(), 2 * tr.getA() , 2 * tr.getB());
	}

	class Trammel {

		double angle;
		double p, q;

		public double x, y; // posisi dari rod
		public double x1, y1 ; // posisi dari pivot 1 
		public double x2, y2 ; // posisi dari pivot 2

		
		double xCorrection; 
		double yCorrection; 
		/*
		 * Dalam Trammel Archimedes, terdapat dua titik pivot yakni A dan B.
		 * Sementara yang men-trace elipse adalah titik C pada ujung trammel.
		 * Jarak A ke B adalah p, sementara jarak B ke C adalah q, dengan
		 * demikian lintasan titik C ditentukan oleh x = (p + q) cos \theta y =
		 * q sin theta.  lihat: http://en.wikipedia.org/wiki/Trammel_of_Archimedes
		 */

		public Trammel(double x, double y, double p, double q, double angle) {
			this.xCorrection = x; 
			this.yCorrection = y; 
			
			this.p = p;
			this.q = q;
			this.angle = angle; 
		}

		
		public void setAngle(double angle) {
			this.angle = angle;
		}

		public void calculatePosition() {
			x = xCorrection+  (p + q) * Math.cos(angle);
			y = yCorrection + (q) * Math.sin(angle);
			
			x1 = x - q * Math.cos(angle); 
			y1 = y -  q * Math.sin(angle);
			
			x2 = x1 -   p * Math.cos(angle); 
			y2 = y1 -   p * Math.sin(angle); 
		}
		
		public double getA(){return (p+q);}
		public double getB(){return q ;}
		public double getXCorrection() {return xCorrection;}
		public double getYCorrection() {return yCorrection; }
	}

}