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]

::::: Opera :::::

If it is practical to place a transparent object between the box and the camera using the Superfly Lighpath "Transparent Depth" might do it. There might be a way to point the spot light at the object. The box on the left shows the actual effect, the box on the right just shows the transparent object as green. Not sure how it would be made to look feathered though. The material node is for the box.

So the nodes are attached to the green object? Then you could simply animate the object, tweak the depth? Is there a way to control the depth of the transparency, I wonder. I'm a FireFly guy, I have not learned/used Superfly, but this could be the moment I learn how.

[edit...]

wait, those nodes are attached to a light, right? You can force a light to "Point At" an object, no problem.

The nodes are attached to the box. The actual disk in front is transparent (left image), I've coloured it green in the right image so you can see it. In Superfly the ray of light travels from the camera through the invisible disk and hits the box, Because the ray has travelled through a transparent object its "Transparent Depth" count is incremented

Thanks for this info and the explanation. So only the mesh of the box receives the transparency, not the contents?

Yes, box only. If the other side of the box needed to be opaque I believe there is another flag called "back facing" that could be used to switch the effect off but haven't tried it. For Firefly the only approach I could think of was to create a mask and then animate the UV offset - that assumes the UV set-up allows it.

Thanks ironsoul.