decloaking and cloaking would be a bear..I suppose you could (winging it here, folks..;) render each frame with a more or less translucent glass material, depending on which way you're going. To be honest, this sounds like a job for Postwork..;)

I wish I'd said that.. The Staircase Wit

anahl nathrak uth vas betude doth yel dyenvey..;)