3d game schreiben.( logik- frage)

import java.awt.Color;
import java.awt.Graphics;

public class Wuerfel {

	private static class D3Vector {

		private double[] r;
		private final int X = 0;
		private final int Y = 1;
		private final int Z = 2;

		public D3Vector(double x, double y, double z) {
			this.r = new double[3];
			this.r[this.X] = x;
			this.r[this.Y] = y;
			this.r[this.Z] = z;
		}

		public double getLength() {
			return (Math
					.sqrt(Math.pow(this.r[this.X], 2)
							+ Math.pow(this.r[this.Y], 2)
							+ Math.pow(this.r[this.Z], 2)));
		}

		public double getX() {
			return this.r[this.X];
		}

		public double getY() {
			return this.r[this.Y];
		}

		public double getZ() {
			return this.r[this.Z];
		}

		public static int[] D3ToD2(int x, int y, int z) {
			int[] ret = new int[2];
			ret[0] = y;
			ret[1] = z;
			return ret;
		}
	}

	private int a;
	private int[] pos;
	private int[] vanishingPoint;
	private D3Vector[] vectors;

	public Wuerfel(int a, int[] pos, int[] vanishingPoint) {
		this.a = a;
		this.pos = pos;
		this.vanishingPoint = vanishingPoint;
		this.vectors = new D3Vector[6];
		this.createVectors();
	}

	private void createVectors() {
		// Waagerecht und horizontal sind trivial
		this.vectors[0] = new D3Vector(0, this.a, 0);
		this.vectors[1] = new D3Vector(0, 0, this.a);
		// Schräg
		int vX = this.vanishingPoint[0] - this.pos[0];
		int vY = this.vanishingPoint[1] - this.pos[1];
		int vZ = this.pos[2] - this.vanishingPoint[2];
		this.vectors[2] = new D3Vector(vX, vY, vZ);
		vX = this.vanishingPoint[0] - this.pos[0];
		vY = this.vanishingPoint[1] - (this.pos[1] + this.a);
		vZ = this.pos[2] - this.vanishingPoint[2];
		this.vectors[3] = new D3Vector(vX, vY, vZ);
		vX = this.vanishingPoint[0] - this.pos[0];
		vY = this.vanishingPoint[1] - this.pos[1];
		vZ = (this.pos[2] - this.a) - this.vanishingPoint[2];
		this.vectors[4] = new D3Vector(vX, vY, vZ);
		vX = this.vanishingPoint[0] - this.pos[0];
		vY = this.vanishingPoint[1] - (this.pos[1] + this.a);
		vZ = (this.pos[2] - this.a) - this.vanishingPoint[2];
		this.vectors[5] = new D3Vector(vX, vY, vZ);
	}

	private void drawVector(Graphics g, D3Vector vector, D3Vector pos) {
		int[] start = D3Vector.D3ToD2((int) Math.round(pos.getX()),
				(int) Math.round(pos.getY()), (int) Math.round(pos.getZ()));
		int[] end = D3Vector.D3ToD2((int) Math.round(vector.getX()),
				(int) Math.round(vector.getY()),
				(int) Math.round(vector.getZ()));

		g.drawLine(start[0], start[1], start[0] + end[0], start[1] - end[1]);
	}

	public void drawCube(Graphics g) {
		int[] vpPos = D3Vector.D3ToD2(this.vanishingPoint[0],
				this.vanishingPoint[1], this.vanishingPoint[2]);

		g.setColor(Color.black);
		g.fillOval(vpPos[0] - 6, vpPos[1] - 6, 10, 10);
		g.drawString("VP", vpPos[0] + 10, vpPos[1] - 10);
		this.drawVector(g, this.vectors[0], new D3Vector(this.pos[0],
				this.pos[1], this.pos[2]));
		this.drawVector(g, this.vectors[0], new D3Vector(this.pos[0],
				this.pos[1], this.pos[2] - this.a));
		this.drawVector(g, this.vectors[1], new D3Vector(this.pos[0],
				this.pos[1], this.pos[2]));
		this.drawVector(g, this.vectors[1], new D3Vector(this.pos[0],
				this.pos[1] + this.a, this.pos[2]));

		this.drawVector(g, this.vectors[2], new D3Vector(this.pos[0],
				this.pos[1], this.pos[2]));
		this.drawVector(g, this.vectors[3], new D3Vector(this.pos[0],
				this.pos[1] + this.a, this.pos[2]));
		this.drawVector(g, this.vectors[4], new D3Vector(this.pos[0],
				this.pos[1], this.pos[2] - this.a));
		this.drawVector(g, this.vectors[5], new D3Vector(this.pos[0],
				this.pos[1] + this.a, this.pos[2] - this.a));
	}

	public void setVanishingPoint(int[] vanishingPoint) {
		this.vanishingPoint = vanishingPoint;
		this.createVectors();
	}

}

import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

import javax.swing.JApplet;

public class DreiD extends JApplet implements MouseListener {

	private Wuerfel wuerfel;

	@Override
	public void init() {
		int[] pos = { 0, 250, 250 };
		int[] vanishingPoint = { 20, 500, 100 };

		this.wuerfel = new Wuerfel(80, pos, vanishingPoint);
		this.setSize(600, 400);
		this.addMouseListener(this);
	}

	@Override
	public void paint(Graphics g) {
		super.paint(g);
		this.wuerfel.drawCube(g);
	}

	@Override
	public void mouseClicked(MouseEvent e) {
		int[] vanishingPoint = { 0, e.getX(), e.getY() };
		this.wuerfel.setVanishingPoint(vanishingPoint);
		this.repaint();
	}

	@Override
	public void mouseEntered(MouseEvent e) {
		// TODO Auto-generated method stub

	}

	@Override
	public void mouseExited(MouseEvent e) {
		// TODO Auto-generated method stub

	}

	@Override
	public void mousePressed(MouseEvent e) {
		// TODO Auto-generated method stub

	}

	@Override
	public void mouseReleased(MouseEvent e) {
	}

}