Making a "I can see ghosts through that object" effect

Unity Engine
1

I want to make an effect which will allow me to see some objects through some other “special” object. So say, for example, there are some ghosts in a game which can only be seen if the player wears some special glasses. Now how do I do that in Unity?

I know that such effect could easily be done using stencil buffer but this is unavailable in Unity so I’m looking for an alternate solution. Any idea?

2

You could put the ghosts on another layer and then activate that layer in the camera when the goggles are on.

3

I’ve used the alpha buffer when I would need a stencil buffer, e.g. here: GLSL Programming/Unity/Mirrors - Wikibooks, open books for an open world
Of course, then you cannot use it for glow or bloom effects.