EDIT: So I've gotten the portal visual effect working with no performance hit, and I've got the physics set up of objects with rigidbodies moving through portals seamlessly, and objects with character controllers moving through it seamlessly. The only thing I'm trying to figure out now is blending two camera views to get the proper first person transition effect. Any ideas on how I'd blend those two? I'm thinking something using a depth only shader, or the normalized viewport rect. My main problem is calculating that in real time, and with angles.
So I've been working on creating a portal effect in Unity3D. Obviously I've taken Valve's Portal as a great influence to programming this. Currently I'm simply using a camera's rendertexture to get the graphical effect across, and then some code to do the rest. The problem is at 2048x2048 it looks as high quality as Portal's, but causes heavy FPS loss. To solve this I'd either have to lower the texture quality or the number of times I update the texture.
Valve has accomplished a high quality portal effect without causing high frame rate loss. How can I do the same? Does anybody have any good ideas for rendering to a high resolution texture without causing frame loss?
I'm considering making my own code for rendering to textures rather then using Unity's built in system, it's doable but would definitely be a hassle. So any thoughts, ideas, or suggestions are highly appreciated.