[RESOLVED] Elliptical orbit

[ThomasJohnsen]

I don't quite follow your code exactly. Why create a graphics object on the main form only to use it in the Paint event, in which a graphics object is already passed as a parameter. Also I think you're making this a tad more complicated than it is. Code below to hopefully give you what you need (or at least illustrate the principle):

RectangleF myrect = new RectangleF(300.0f, 150.0f, 30.0f, 30.0f);
        RectangleF myorbit = new RectangleF(200.0f, 100.0f, 115.0f, 65.0f);
        float ellipse_angle = 0.0f;
        float rotation_angle = 0.0f;
 
        private void Main_Paint(object sender, PaintEventArgs e)
        {
            e.Graphics.DrawEllipse(Pens.Red, myorbit.X, myorbit.Y, myorbit.Width, myorbit.Height);
 
            using (System.Drawing.Drawing2D.Matrix transformation = new System.Drawing.Drawing2D.Matrix() { })
            {
                transformation.Translate(myrect.X, myrect.Y);
                transformation.Rotate(rotation_angle);
                transformation.Translate(-myrect.X, -myrect.Y);
 
                e.Graphics.Transform = transformation;
            }
 
            e.Graphics.DrawRectangle(Pens.AntiqueWhite, myrect.X, myrect.Y, myrect.Width, myrect.Height);
        }
 
        private void timerxoay_Tick(object sender, EventArgs e)
        {
            ellipse_angle += (float)(Math.PI / 40.0);
            rotation_angle += (float)(Math.PI / 10.0);
            myrect.Location = new PointF(myorbit.X + (float)((Math.Cos(ellipse_angle) + 1.0) * myorbit.Width / 2.0),
                                         myorbit.Y + (float)((Math.Sin(ellipse_angle) + 1.0) * myorbit.Height / 2.0));
            this.Invalidate();
        }
 
        private void cmdrotate_Click(object sender, EventArgs e)
        {
            timerxoay.Enabled = !timerxoay.Enabled;
        }

Regards Tom