It would be nice to have two options for reflections, one for the vehicle itself, and one for the mirrors on the vehicle. It would be less laggy because the reflections on the vehicle wouldn't be rendering if you disabled Dynamic Reflections for vehicles, but not mirrors.
if you're rendering a dynamic cubemap, you get the whole thing, so you might as well apply it to the whole car. The mirrors currently work by just being a reflective part of the car which receives a dynamic cubemap when dynamic reflections are enabled - you'd have to set up cameras at each mirror to have it only render what the mirror is reflecting. EDIT: well, LJFHutch liked this post, I guess I said something right
Yep, dynamic cubemaps are a "cheap" way to have usable mirrors. Not great, as you can see by the pixelation and artifacts, but no additional cost if the cubemap is being rendered anyways. The more "proper" way to do it would be to place cameras at each mirror, which would most likely have a huge performance overhead.
Considering a cube map requires six renders (one for each face), a very basic render-to-texture implementation could even reduce performance requirements, by reducing it to either a single render for all mirrors, or three renders, with one for each mirror. I have no idea what overhead is introduced by actually setting this up in T3D though, and that alone could easily offset the performance gains.
