Make an object move towards another objects positi

问题:

What I have currently is two objects that can be played though nav keys and the other one with wasd. The point is to get the 3rd object and score a point, and it randoms a new pos after catching it, which works.

Now... I want the npc2 to not longer be controlled by human, and create a method for it to move on its own TOWARDS the scoring object. How would I possibly do to achieve this? Im new to c# :)

FORM.cs below

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

namespace SPEL
{
    public partial class Form1 : Form
    {
        npc npc1 = new npc();
        npc npc2 = new npc();
        sten ste1 = new sten();
        int poang1 = 0;
        int poang2 = 0;
        private _keyControl cc = new _keyControl();

        public Form1()
        {
            SetStyle(ControlStyles.UserPaint, true);
            SetStyle(ControlStyles.AllPaintingInWmPaint, true);
            SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
            InitializeComponent();

            // Hantera tangentbordet
            #region captute evenents
            this.KeyDown += new System.Windows.Forms.KeyEventHandler(cc.addKey);
            this.KeyUp += new System.Windows.Forms.KeyEventHandler(cc.delKey);
            #endregion
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            npc1.Rita(e.Graphics);
            npc2.Rita(e.Graphics);
            ste1.Draw(e.Graphics);



        }

        private void Form1_KeyDown(object sender, KeyEventArgs e)
        {
            //MessageBox.Show(e.KeyData.ToString());




        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            //spelare 1
            this.Text = cc.keyStr;
            if (cc.getKey("Right"))
            {
                npc1.Flytta("Right");
                this.Invalidate();
            }
            if (cc.getKey("Left"))
            {
                npc1.Flytta("Left");
                this.Invalidate();
            }
            if (cc.getKey("Up"))
            {
                npc1.Flytta("Up");
                this.Invalidate();
            }
            if (cc.getKey("Down"))
            {
                npc1.Flytta("Down");
                this.Invalidate();
            }
                //Spelare 2
                if (cc.getKey("D"))
                {
                    npc2.Flytta("Right");
                    this.Invalidate();
                }
                if (cc.getKey("A"))
                {
                    npc2.Flytta("Left");
                    this.Invalidate();
                }
                if (cc.getKey("W"))
                {
                    npc2.Flytta("Up");
                    this.Invalidate();
                }
                if (cc.getKey("S"))
                {
                    npc2.Flytta("Down");
                    this.Invalidate();
                }

            if (npc1.checkkoll().IntersectsWith(ste1.checkkoll()))
            {
                poang1++;
                ste1.randomxy(this.Width -30, this.Height -30);


            }
            if (npc2.checkkoll().IntersectsWith(ste1.checkkoll()))
            {
                poang2++;
                ste1.randomxy(this.Width -30, this.Height -30);
            }


        }

        private void timer2_Tick(object sender, EventArgs e)
        {
            if (this.BackColor == Color.Red)
                this.BackColor = Color.Blue;
            else
                this.BackColor = Color.Red;
        }

        private void flytta_Tick(object sender, EventArgs e)
        {


            }
        }
    }
}

And here's my movement class

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;

namespace SPEL
{
    class npc
    {
        private Bitmap strid;
        private Point pt;
        public npc()
        {
            strid = new Bitmap("hej.gif");

            pt.X = 20;
            pt.Y = 20;

        }

        public void Rita(Graphics f)
        {
            Rectangle re = new Rectangle(pt.X, pt.Y, strid.Width, strid.Height);
            f.DrawImage(strid, re);
        }

        public Rectangle checkkoll()
        {
            Rectangle re = new Rectangle(pt.X, pt.Y, strid.Width, strid.Height);
            return re;
        }

        public void Flytta(string dir)
        {

            if (dir == "Left")
            {
                pt.X = pt.X - 2;
            }
            if (dir == "Right")
            {
                pt.X = pt.X + 2;
            }
            if (dir == "Up")
            {
                pt.Y = pt.Y - 2;
            }
            if (dir == "Down")
            {
                pt.Y = pt.Y + 2;
            }
        }

    }
}

I do understand that it's much to ask for, but i'd be more than thankful if you could help me!

回答1:

Try something like this

    public void FlyttaMot(int x, int y, float speed)
    {
        float tx = x - pt.X;
        float ty = y - pt.Y;
        float length = Math.Sqrt(tx*tx + ty*ty);
        if (length > speed)
        {
            // move towards the goal
            pt.X = (int)(pt.X + speed* tx/length);
            pt.Y = (int)(pt.Y + speed* ty/length);
        }
        else
        {
            // already there
            pt.X = x;
            pt.Y = y;
        }
    }

Call it from your timer tick code in Form.cs like this for example.

npc2.FlyttaMot(200, 200, 0.5f);

I based this on linear algebra. Take a look at this video for example. The (tx,ty) is the vector in which direction the npc should go. Dividing with the length of the vector gives us a vector of length 1. I multiply this with a speed parameter so you can adjust the speed of the npc.

回答2:

The easiest and most accurate way, is to rely on vector geometry.

Define class

public class Vector2 {

     public float x {get;set;}; 
     public float y {get;set;}; 

     public Vector2(float a_x, float a_y, float b_x, float b_y)
     {
        x = b_x - a_x;
        y = b_y - a_y;
     }

     //calculate vector length
     public float Length {
          get {
               return Math.Sqrt((x * x) + (y * y));
          }
     }

     public void SetVectorLength(float desiredLength){
            double r = desiredLength/ this.Length;
            this.x *= r;
            this.y *= r;
     }

}

this is just a set of functions for this case, but you can add others, plenty of them need for various parts of your calculations.

After what you have to do is just, calculate next position of your vertex toward the directional vector.

//hypothetical X coordinate
float x_coord = 1.34f; 

//move towards the vector 
var vector = new Vector2(10, 10, 20, 20);

//set vector move step 
vector.SetLength(0.1f);

var movedX = x_coord + vector.x;

Repeat: this is just hypothetical example, you need to work on this. It's hard to put in small answer all related vector geometry stuff.