BJ

------------------------------BallisticSimulator---------------------

using System;
using System.Drawing;

namespace CannonBallGame
{
	/// <summary>
	/// A simple Ballistics simulator class
	/// </summary>
	public class BallisticSimulator
	{
		public float InitialAngle = 0.0f;
		public float InitialVelocity = 100.0f;
		public float ElapsedTime = 0.0f;
		public float Timestep = 1.0f;


		public BallisticSimulator()
		{
			
		}

		/// <summary>
		/// Gets the next position of the simulator by incrementing the ElapsedTime
		/// </summary>
		/// <returns>The next position as a PointF</returns>
		public PointF GetNextPosition()
		{
			ElapsedTime += Timestep;

			// Convert InitialAngle to radian, radian = degrees * (PI/180)
			float fIA = InitialAngle * (float)(Math.PI/180.0f);

			// Find X and Y values at time “current“
			float fX = (float)((InitialVelocity * Math.Cos(fIA) * ElapsedTime)) / 2.0f;
			float fY = (float)(((InitialVelocity * Math.Sin(fIA) * ElapsedTime) - (0.5f * 9.8f * (ElapsedTime * ElapsedTime))) / 2.0f);
			PointF pt = new PointF(fX, fY);

			return pt;
		}
	}
}



-------------------------CannonBallForm------------------------------------
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Text;
using System.Windows.Forms;
using System.Threading;

namespace CannonBallGame
{
    public partial class CannonBallForm : Form
    {
        private int angle;
        private int velocity;
        private int height;
        private Thread projectile;
        private BallisticSimulator cannonSim;
        // The next position to plot
        private PointF pointNextPosition = new PointF();
        // The size of the dot to draw
        private SizeF projectileSize = new SizeF(5.0f, 5.0f);

        public CannonBallForm()
        {
            InitializeComponent();

            cannonSim = new BallisticSimulator();
        }

        ///<summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            //Application.EnableVisualStyles();
            //Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new CannonBallForm());
        }

        

        private void Run()
        {
            try
            {
                Cannon c = new Cannon(graphicsPanel, angle, velocity, height);
                c.fire();
            }
            catch (ThreadAbortException)
            { }
            finally 
            {
                bigRedButton.Enabled = true;
            }
        }

        private void angleSelect_ValueChanged(object sender, EventArgs e)
        {
            angle = (int)angleSelect.Value;
        }

        private void velocitySelect_ValueChanged(object sender, EventArgs e)
        {
            velocity = (int)velocitySelect.Value;
        }

        private void heightSelect_ValueChanged(object sender, EventArgs e)
        {
            height = (int)heightSelect.Value;
        }

        private void bigRedButton_Click(object sender, EventArgs e)
        {
            bigRedButton.Enabled = false;
            timer1.Enabled = true;
            cannonSim.InitialAngle = angle;
            cannonSim.InitialVelocity = velocity;
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            // On tick, increment simulator and plot next point on trajectory
            PlotPoint(cannonSim.GetNextPosition());
        }

        public void Reset()
        {
            pointNextPosition = new Point(0, 0);
        }

        public void PlotPoint(PointF point)
        {
            pointNextPosition = point;
            // We could invalidate just around this point for better performance
            //graphicsPanel.Invalidate();
            Graphics g = graphicsPanel.CreateGraphics();
            
            // Setup a transform that puts (0,0) at the bottom left corner
            Matrix xform = new Matrix();
            xform.Scale(1.0f, -1.0f);
            xform.Translate(0, -(graphicsPanel.Height - height));
            g.Transform = xform;

            // Smooooth!
            g.SmoothingMode = SmoothingMode.AntiAlias;

            // Draw the projectile
            RectangleF rect = new RectangleF(pointNextPosition, projectileSize);
            rect.Offset(-projectileSize.Width / 2.0f, -projectileSize.Height / 2.0f);
            g.FillEllipse(Brushes.Blue, rect);
        }
    }
}