Procedural or map?

Let's say I have a big box on the stage, with things in it. The box has a cool texture map with grime, cardboard edges, labels, etc. I want to render a 600-frame walk-around, with a magic spotlight (flashlight) with a narrow shotgun focus on the box, and everywhere I point it produces a feathered circle of transparency, revealing the contents.

I suppose you could shift the movement of a transparency map one frame at a time? But is there a way to automate a spotlight to "burn" the transparency spot onto the box?

What is the approach in Poser?

Any clues, hints, advice and links welcome. [hope bb sees this]

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