（Java）中心3D多边形位置

Question

我需要一种方法来将自定义3D多边形围绕它的位置（质心）居中。我制作了一个获取质心的方法，但我需要一种方法将多边形移动到指定的质心。

我想这样做，所以PerspectiveProjection类只需要投射1个Vector3（位置）而不是所有多边形的结。

Polygon3D类：

public class Polygon3D extends Colored implements Shape {
private List<Vector3> knots;
// Position = center of polygon.
private Vector3 position;
private Polygon poly;

public Polygon3D() {
    this(new ArrayList<Vector3>());
}
public Polygon3D(List<Vector3> knots) {
    this(knots, new Vector3());
}
public Polygon3D(List<Vector3> knots, Vector3 position) {
    this(knots, position, Color.GRAY);
}
public Polygon3D(List<Vector3> knots, Vector3 position, Color color) {
    this.knots = knots;
    setColor(color);
    this.position = position;
    ShapeManager.registerShape(this);
    this.poly = toPolygon();
}

public List<Vector3> getKnots() {
    return this.knots;
}
public void setKnots(List<Vector3> knots) {
    this.knots = knots;
    this.poly = toPolygon();
}
public void addKnot(Vector3 knot) {
    if (this.knots.contains(knot))
        return;
    this.knots.add(knot);
    this.poly = toPolygon();
}
public void removeKnot(Vector3 knot) {
    this.knots.remove(knot);
    this.poly = toPolygon();
}
public Vector3 getPosition() {
    return this.position;
}
public void setPosition(Vector3 position) {
    this.position = position;
}

public Vector3 getCentroid() {
    double centroidX = 0, centroidY = 0, centroidZ = 0;
    for (Vector3 knot : this.knots) {
        centroidX += knot.getX();
        centroidY += knot.getY();
        centroidZ += knot.getZ();
    }
    return new Vector3(centroidX / this.knots.size(), centroidY / this.knots.size(), 
            centroidZ / this.knots.size());
}
public List<Vector2> get2DKnots() {
    List<Vector2> knots = new ArrayList<>();
    Camera camera = PaintPanel.mainCamera;
    Projection3D project = camera.getProjection();
    OrthographicProjection op = null;
    PerspectiveProjection pp = null;
    if (project instanceof OrthographicProjection)
        op = (OrthographicProjection) project;
    else
        pp = (PerspectiveProjection) project;
    // Get knots from orthographic projection
    if (op != null) {
        for (Vector3 knot : this.knots) {
            knots.add(op.project(knot, new Vector3(1, 1, 1), new Vector3(0, 0, 0)));
        }
    }
    // Get knots from perspective projection
    else {
        for (Vector3 knot : this.knots) {
            knots.add(pp.project(knot, camera));
        }
    }
    return knots;
}
public Polygon toPolygon() {
    // Converts all the 3D knots to 2D points on the screen and adds them to a new polygon.
    Polygon poly = new Polygon();
    for (Vector2 vec : get2DKnots()) {
        poly.addPoint(vec.toPoint().x, vec.toPoint().y);
    }
    return poly;
}

public void draw(Graphics g) {
    g.setColor(Color.BLACK);
    g.drawPolygon(this.poly);
    g.setColor(getColor());
    g.fillPolygon(this.poly);
}
}

（顺便说一下，我在8年级：p）