多边形在旋转时会收缩

Question

我对6点的轮换感到不满.这些点围绕中间的中心点旋转.但是会发生的是形状区域缩小,变得越来越小.

形状的绘图在带有PaintComponent的i JPanel上进行.这意味着画布只支持整数定位,尽管我可以在双打中存储位置.

我使用Point2D.Double存储点位置I在每个函数调用时将所有点旋转1个deegre

我认为我对旋转的理解是缺乏的,我可以在一次调用中旋转360 deegre,或180,这样可以正常工作.但45 deegres或90将完全把我的点变成一条线(下图).

这个问题一直困扰着我一段时间,但一如既往,我确信有一个简单的解决方案.

这是旋转功能

@Override
public synchronized void rotatePoints(int move_x, int move_y) {
    // TODO Auto-generated method stub
    super.rotatePoints(move_x, move_y);

    BottomPanel.appendText("Area of Polygon is: " + UtilClass.calculateAreaOfPolygon(points)+ "\n");

    double degrees=1.0;
    double radians = degrees * (double)(Math.PI / 180.0);

    //GET THE CENTER POINT C
    Point2D.Double center = UtilClass.getCenterOfPolygon(points);

    //ITERATE THROUGH THE POINTS
    Iterator<PointClass> itr = points.iterator();

    while(itr.hasNext()) {

        //GET THE POINT
        PointClass point_class = itr.next();
        //point_class = points.get(3);

        //FIRST TRANSLATE THE DIFFERENCE
        double x1 = point_class.point.x - center.x;
        double y1 = point_class.point.y - center.y;

        //APPLY ROTATION MATRIX
        x1 = (x1 * Math.cos(radians)) - (y1 * Math.sin(radians));
        y1 = (x1 * Math.sin(radians)) + (y1 * Math.cos(radians));

        //TRANSLATE BACK
        point_class.point.setLocation(x1 + center.x, y1 + center.y);

        //ADD THE DEEGRES TO POINT CLASS
        point_class.angle += Math.toDegrees(radians);
    }
}

这是用于检索给定多边形的中心位置的代码

public synchronized static Point2D.Double getCenterOfPolygon(List<PointClass> points) {

    //GETTING THE CENTER OF A COMPLEX POLYGON

    double combined_x = 0;
    double combined_y = 0;

    Iterator<PointClass> itr = points.iterator();

    while(itr.hasNext()) {

        PointClass point_class = itr.next();

        //ADD TO THE
        combined_x += point_class.point.x;
        combined_y += point_class.point.y;
    }

    double center_x = combined_x / (double)points.size();
    double center_y = combined_y / (double)points.size();

    return new Point2D.Double(center_x, center_y);
}

这是一个形状的图片,其所有点顺时针旋转1 deegre

每次旋转后,我输出多边形的区域就是结果

• 多边形面积是:6290
• 多边形面积是:6288
• 多边形面积是:6286
• 多边形面积是:6284
• 多边形面积是:6283
• 多边形面积是:6281

---

这是一张形状的图片,在一次通话后顺时针方向旋转90度.它显然不想这样做.

我会很高兴任何建议或提示.

Answer 1

错误在于:

//APPLY ROTATION MATRIX
x1 = (x1 * Math.cos(radians)) - (y1 * Math.sin(radians));
y1 = (x1 * Math.sin(radians)) + (y1 * Math.cos(radians));

x1正在更新太早,这y1是基于新值x1而不是旧值计算的.

您可以将其更改为以下内容:

//APPLY ROTATION MATRIX
double temp;
temp = (x1 * Math.cos(radians)) - (y1 * Math.sin(radians));
y1   = (x1 * Math.sin(radians)) + (y1 * Math.cos(radians));
x1   = temp;