Void like portal effect in Unity Free

Unity Engine
1

Through some miracle of circumstance, I was able to accomplish a very simple portal effect similar to that in the game Void in Unity free. Unfortunately, I’ve lost the file I did it in and I have NO IDEA how I managed to pull it off. For those unfamiliar, in the game Void, you open temporary portals to the past that occupy a spherical area in the level space. The effect can be seen here:

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I don’t need the distortion effect or anything. I can fake the edges of the portal easily enough, but I really need that “hole in time” portal effect for a gameplay concept I’m trying out. Does anyone know how this can be accomplished in Unity free?

2

I think I can pull this off with a depth mask shader and two cameras, but I can’t figure out how, exactly. The first time I did it, I just managed to pull off some weird layer trickery, but the exact implementation isn’t as important as having it outright function.

3

Really wish I could help with this. It sounds awesome! Did you ever sort it out?