protected static IEnumerable <Kn5RenderableDepthOnlyObject> Flatten(RenderableList root, Func <IRenderableObject, bool> filter = null)
{
return(root
.SelectManyRecursive(x => {
var list = x as Kn5RenderableList;
if (list == null || !list.IsEnabled)
{
return null;
}
return filter?.Invoke(list) == false ? null : list;
})
.OfType <Kn5RenderableDepthOnlyObject>()
.Where(x => x.IsEnabled && filter?.Invoke(x) != false));
}