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POPhysics Project in C#: Problems with threading and measuring time
 

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  1. POPhysics Project in C#: Problems with threading and measuring time
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    <p>I'm having some problems with a physics project I'm trying to make. Its basically a Free Fall simulator. I set the gravitational acceleration and the height and the program should simulate the fall. The problem is that it's getting the time wrong, don't know why. I'm using the Stopwatch class for measuring the time.</p> <p>Here's the code:</p> <p>FrmMain.cs:</p> <pre><code>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; using System.Threading; using System.Diagnostics; namespace Physics { public partial class FrmMain : Form { public Settings config = new Settings(); public float displacement = 0f; public Stopwatch timer = new Stopwatch(); public float timeElapsed; //in Seconds public Thread thread; public FrmMain() { InitializeComponent(); //New thread (Drawing) thread = new Thread(new ThreadStart(Drawing)); thread.IsBackground = true; thread.Start(); this.KeyDown +=new KeyEventHandler(FrmMain_KeyDown); } private void Drawing() { try { while (true) { if (config.objectPos.Y &lt; config.sizeBitmap.Height) timer.Start(); else timer.Stop(); Bitmap screen = new Bitmap(this.pboxScreen.Width, this.pboxScreen.Height); SendScreen(screen); } } catch (ThreadAbortException tae) { Console.WriteLine(tae.Message); } } private void SendScreen(Bitmap Screen) { if (pboxScreen.InvokeRequired) { pboxScreen.Invoke(new MethodInvoker(delegate() { this.SendScreen(Screen); })); } else { //Converting Milliseconds to Seconds timeElapsed = timer.ElapsedMilliseconds / 1000f; //Check if object isn't in the ground if (config.objectPos.Y &lt; config.sizeBitmap.Height) { displacement -= config.objectPos.Y; config.objectPos.Y = config.objectPos.Y + 0.5f * config.acceleration * timeElapsed * timeElapsed; displacement += config.objectPos.Y; } Graphics g = Graphics.FromImage(Screen); g.Clear(Color.White); //New rectangle Rectangle rec = new Rectangle((int)config.objectPos.X, (int)config.objectPos.Y, 5, 5); g.FillRectangle((new Pen(Color.DarkRed)).Brush, rec); g.DrawRectangle(new Pen(Color.Red, 2.0f), rec); g.Dispose(); //Update txtbox (textbox) txtboxX.Text = config.objectPos.X.ToString(); txtboxY.Text = config.objectPos.Y.ToString(); txtboxTempo.Text = timeElapsed.ToString(); txtboxD.Text = displacement.ToString(); pboxScreen.Image = Screen; } } void FrmMain_KeyDown(object sender, KeyEventArgs e) { switch (e.KeyCode) { case Keys.Space: if (config.objectPos.Y &gt;= config.sizeBitmap.Height) { config.objectPos.Y -= 100; timer.Reset(); } break; } } private void FrmMain_FormClosing(object sender, FormClosingEventArgs e) { if (thread.IsAlive) thread.Abort(); } } } </code></pre> <p>Settings.cs:</p> <pre><code>using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Drawing; namespace Physics { public class Settings { public Size sizeBitmap; //bitmap resolution public PointF objectPos; //Initial Position public float acceleration; public Settings() { sizeBitmap.Width = 560; sizeBitmap.Height = 420; objectPos.X = 560f / 2f; objectPos.Y = 420f / 2f; acceleration = 9.8f; } } } </code></pre> <p>There's another problem, depending on height the object doesn't fall without interruption, it stay in the same position for a few, but noticeable, milliseconds. I think this is a threading problem, 'cause it's been a while I don't use it, so I might be missing something.</p> <p>I'm measuring the height in meters, so the objectPos.Y = 420f / 2f represent a height of 210 meters. For this height, the object should take around 6.5 seconds to hit the ground, in my program it's taking less than 1 second, so I assumed that there's a time measuring problem.</p> <p>I'm calculating the height with the uniform gravitational field without air resistance expression :</p> <blockquote> <p>h(t)=h0+0.5*g*t²</p> </blockquote> <p>where: <em>h(t)</em> is the height with respect to time, <em>h0</em> the initial altitude, <em>g</em> acceleration due to gravity and <em>t</em> the time elapsed</p> <p>Any help is much appreciated. Thanks.</p>
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