水立方.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Shuilifang
{
    public partial class Form1 : Form
    {
        private List<PointF> _points = new List<PointF>();
        private Graphics _g;
        private int _iters = 0;
        private Random _rnd = new Random();

        private Bitmap _bmp0 = null;

        private const int TCOUNT = 1000;
        private PointF[] _turtles = new PointF[TCOUNT];

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            pictureBox1.Image = new Bitmap(pictureBox1.Width, pictureBox1.Height);
            _g = Graphics.FromImage(pictureBox1.Image);
        }

        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == System.Windows.Forms.MouseButtons.Right)
            {
                pictureBox1.Image = new Bitmap(pictureBox1.Width, pictureBox1.Height);
                _g = Graphics.FromImage(pictureBox1.Image);
                _points.Clear();
                _iters = 0;
            }
            else
            {
                _points.Add(new PointF(e.X, e.Y));
                _g.FillRectangle(Brushes.Red, (int)e.X - 5, (int)e.Y - 5, 10, 10);
                pictureBox1.Refresh();
            }
        }

        private void pictureBox1_DoubleClick(object sender, EventArgs e)
        {
        }

        private PointF calcForce(PointF p, PointF t)
        {
            PointF vec = new PointF(t.X - p.X, t.Y - p.Y);
            float mlen = vec.X * vec.X + vec.Y * vec.Y;
            mlen *= (float)Math.Sqrt(mlen);
            vec.X /= mlen; vec.Y /= mlen;
            return vec;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            for (int iting = 0; iting < 100; ++iting)
            {
                Application.DoEvents();
                if (_iters == 0)
                {
                    _bmp0 = (Bitmap)pictureBox1.Image.Clone();
                    for (int i = 0; i < TCOUNT; ++i)
                    {
                        _turtles[i].X = _rnd.Next(pictureBox1.Width);
                        _turtles[i].Y = _rnd.Next(pictureBox1.Height);
                    }
                }
                else
                {
                    for (int i = 0; i < TCOUNT; ++i)
                    {
                        // 计算排斥力
                        int flen = 100;
                        PointF force = new PointF(0, 0);
                        var t = _turtles[i];
                        foreach (var p in _points)
                        {
                            var vec = calcForce(p, t);
                            force.X += vec.X * flen; force.Y += vec.Y * flen;
                        }
                        // 计算到四个边的排斥力
                        flen /= 10;
                        for (int x = 0; x < _bmp0.Width; ++x)
                        {
                            var vec = calcForce(new PointF(x, 0), t);
                            force.X += vec.X * flen / 10; force.Y += vec.Y * flen / 10;
                            vec = calcForce(new PointF(x, _bmp0.Height), t);
                            force.X += vec.X * flen / 10; force.Y += vec.Y * flen / 10;
                        }
                        for (int y = 0; y < _bmp0.Height; ++y)
                        {
                            var vec = calcForce(new PointF(0, y), t);
                            force.X += vec.X * flen / 10; force.Y += vec.Y * flen / 10;
                            vec = calcForce(new PointF(_bmp0.Width, y), t);
                            force.X += vec.X * flen / 10; force.Y += vec.Y * flen / 10;
                        }
                        _turtles[i].X += force.X; _turtles[i].Y += force.Y;
                    }
                }
                _iters++;
                this.Text = "Iter: " + _iters;
            }

            pictureBox1.Image = (Bitmap)_bmp0.Clone();
            using (Graphics g = Graphics.FromImage(pictureBox1.Image))
            {
                for (int i = 0; i < TCOUNT; ++i)
                {
                    g.FillRectangle(Brushes.Blue, _turtles[i].X, _turtles[i].Y, 2, 2);
                }
            }
            pictureBox1.Refresh();
        }
    }
}