计算星星的五个角 - 方法无法正常工作

Question

我想计算五角星的五个角。我将第一个点设置在 x = 0.0 和 y = 1.0 的顶部。第二个点的第一次计算是正确的，因为该方法从点数组中获取值。

但是第三点的第二次计算不行。因为它取的是第一次计算的值。当我从点数组中获取新值时，逗号可能有问题。 --> (. and ,) 计算中的值类型总是double并且是正确的。

问题：我总是得到星角最后三个位置的输出0, 0

using System;
using System.Drawing;
using System.Windows.Forms;
using System.Threading;
using System.Diagnostics;

// draw a 5 point star

namespace WindowsFormsApplication10
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            System.Drawing.Pen myPen = new System.Drawing.Pen(System.Drawing.Color.Red);
            Graphics g = this.CreateGraphics();

            double[,] points = new double[5, 2] {
                { 0.0, 1.0 },
                { 0.0, 0.0 },
                { 0.0, 0.0 },
                { 0.0, 0.0 },
                { 0.0, 0.0 }
            };

            // debuging
            // first value?                 correct
            // calculation second value?    correct
            // problem: doesn't take second value to calculation
            //          type --> is always double

            // calculation
            for (int i = 0; i < 5; i++)
            {
                double[] newVector = RotateVector2d(points[i, 0], points[i, 1], 2.0*Math.PI/5);   // degrees in rad !
                points[i, 0] = newVector[0];
                points[i, 1] = newVector[1];
                Debug.WriteLine(newVector[0] + " " + newVector[1]);
            }

            // drawing
            for (int i = 0; i < 5; i++)
            {
                g.DrawLine(myPen, 100, 100, 100 + 50*Convert.ToSingle(points[i,0]) , 100 + 50*Convert.ToSingle(points[i, 1]));
            }

            myPen.Dispose();
            g.Dispose();
        }

        static double[] RotateVector2d(double x, double y, double degrees)
        {
            Debug.WriteLine("calculating rotation");
            double[] result = new double[2];
            result[0] = x * Math.Cos(degrees) - y * Math.Sin(degrees);
            result[1] = x * Math.Sin(degrees) - y * Math.Cos(degrees);
            return result;
        }
    }
}

Answer 1

您可能想要旋转前一个矢量而不是当前矢量：

for (int i = 1; i < 5; i++)
{
    double[] newVector = RotateVector2d(points[i - 1, 0], points[i - 1, 1], 2.0*Math.PI/5);   // degrees in rad !
    points[i, 0] = newVector[0];
    points[i, 1] = newVector[1];
    Debug.WriteLine(newVector[0] + " " + newVector[1]);
}

计算星星的五个角 - 方法无法正常工作

Calculate the five corners of a star - method doesn't work correctly

c#

parameter-passing