2 way mirror box

Ok, here’s one for you. How would you build a box of 1 way mirrors? Reflective on one side. Transparent on the other. Look at the link to see what I’m looking for. It sounds straight forward. Use 2 materials, but it doesn’t work. Not sure if you need to use the light paths node or what.


That might actually be easier than you think (this is just 4 bounces - the more, the merrier):

It’s not perfect, though, as there is no light getting into that cube from the outside…

Very nice. Thanks. Yeah I think they used lights in the edges too, but some light should penetrate into the box. This is what I was looking for though. Thanks again. Why is it all wavy like that?

Working on it…:wink:
I can get the light into the box from the outside now, but then lose the “eternal” reflection of lights inside that box.

Oh, and the wavyness is from a subtle displacement modifier.

2 way mirrors are actually just slightly transparent mirrors with a bright light source on only one side. People on the dark side can see in because lots of light is coming from the other side, but people on the bright side can’t see out except very dimly if they look close. Mixing a glass and glossy shader in Cycles with a high bounce count and a bright light inside a solidified cube should do the trick. In that picture they have light bars running along the edges of the cube, and note that its faces are flexible. Here’s an example where I’ve made a shape key to create that convex/concave behavior seen in that article. You’ll have to play with the render settings to get a pretty result, but here’s a quick render at 100 samples.

And here’s the .blend file so you can play with it. 2WayCube.blend (247 KB)

Yep this was a good question to ask. Great responses.

Minor update with some material, lighting and render tweaks. Just changing values to get a better look.

Convex cube:

Concave cube:

New file: 2WayCube.blend (247 KB)