"Lit" and "unlit" texture effect

I assume this is a texture question but it might be a building or scripting one, so sorry if this ends up in the wrong part of the forum.

I was wandering around the mall in Itland and came across a store that had a couple of windows with images "behind" them. When you look at the images straight on, they appear "lit", as if a light behind them has been turned on. When you move your viewing angle to one side or the other, it's as if the "light" goes out. The image is still clearly there but now it's dark. Only the specific image is affected by this, not the window itself or anything around it. The overall effect is very striking, as if you're looking into a RL window display with and without lights. The effect is more obvious of course when you have world sun set to midnight.

I could tell that the images weren't part of the actual window, they seem to be sandwiched between the "window pane" and some kind of backboard, but for the life of me I can't see how they got the effect. Is it scripted do you think?

I'd love to know how it's done if anyone has any ideas.

Thanks
Isobel

Sounds like maybe clever use of the alpha sorting glitch to me. If you put a dark translucent panel directly behind the slightly translucent picture panel, you might very well see the picture as "in front" when viewing it straight on, and than have it flip to "in back" when viewing it from a more oblique angle. When the dark panel is "in front" it would appear to dim the picture.

Making the effect entirely predictable would be difficult, though. But that's my best guess at what's happening, based on your description of the setup.

That's interesting Chosen, I didn't think of that. The effect is very clear cut though, no flashing or bit of lit texture showing through the dark etc. I think you must be right that there are two textures involved but something else is making them switch so predictably.

If anyone would like to see this in action I'm happy to go back and get the slurl. It struck me because I've never seen this done anywhere else.

Isobel

Would love to see it inworld too... are you viewing it in WL?

My evil eye has transparency and is set to full bright. It does the same thing with my glasses. (^_^)

No WL .. still using Nicholas viewer based on 1.18.5 (3).

This is the slurl
http://slurl.com/secondlife/ITLAND/134/3/21

and it's the orange dress that has the effect.