Create special-shaped windows

Hello,

I know Microsoft Dancer (inside the Plus! package) is able to make windows with a shape and a content that is always changing, like the "dancers" do. And I'm sure it doesn't use the SetWindowRgn function of Windows since it's too fast. So that must be DirectX.

Does someone know how to reproduce this

Thanks a lot.

Game Technologies: DirectX, XNA, XACT, etc.9