/// <summary>
/// Create the GO that acts as the "handle", ie identifies selected position on timelin
/// Default is a kind of ugly large triangle underneath midline...
/// Override to provide your own visuals. Return null for no handle.
/// </summary>
protected virtual fGameObject create_handle_go(fMaterial handleMaterial)
{
fTriangleGameObject handle = GameObjectFactory.CreateTriangleGO(
"handle", Height, Height, handleMaterial.color, true);
MaterialUtil.DisableShadows(handle);
handle.RotateD(Vector3f.AxisX, -90.0f); // ??
return(handle);
}