ILayer::Draw is not called on my custom layer (C++ and OpenGL).

hi,

I am trying to create a custom layer in C++ and OpenGL for ArcScene.
I have implemented ILayer, IGeoDataset and IGraphicsContainer3D.
The layer is added to the scene and shows up in the TOC.

When I move the camera in ArcScene, IGeoDataset::get_Extent is called
repeatedly but ILayer::Draw is only called a single time just as the
layer is added to the scene.

How do I get ILayer::Draw to be called whenever the camera in my scene
is moved?