void HandleMouseWheel(object sender, MouseEventArgs e)
{
Ray pointer = viewport.GetPointerRay(e.Location);
viewport.Zoom(pointer, -e.Delta / 120);
this.Invalidate();
}
void UserControl1_MouseWheel(object sender, MouseEventArgs e)
{
//viewport.zoom(e.Delta / 120);
//Vector2 location = viewport.TransformToViewport(ClientRectangle, e.Location);
viewport.Zoom(new Vector2(e.Location.X, e.Location.Y), -e.Delta / 120);
this.Invalidate();
}