Awesome

Unity-Portals

Portal rendering in Unity by not using RenderTextures!

Instead uses shader magic camera replacement shaders, the stencil buffer and oblique projection (thanks to pr0g for that!).

Limitations:

• Requires forward rendering
• The world inside the portals is rendered using a non-standard shader (legacy bumped specular)
• Does not work with skyboxes or camera background color
• No moving through the portals, yet

You can add more subshaders to the Portal Replacement shaders for "advanced" features like transparency.

Controls:

Mouse - look around
WASD - move around
E & Q - ascend and descend
Shift - move faster
Control - move slower
End - unlock/lock cursor