uh realtime clipping may be too slow. I just tested it with a sphere with 100 Segments (that's about 40k tris) and my framerate drops to 150ms per frame on a Radeon 9200se.
Rendering with the same amount of polies, but using a precalculated clipped version for the EnvMap was done in 33ms/f on this machine (total 80kTris for the normal Renderworld, inclusive water quad and of course, the clipped quad in the 6*EnvMap Update).
BTW if you would use a relative small EnvMap resolution, it may be possible to use 6 cameras, each one with its own CameraViewport and angle, then create the Cubemap with a single renderworld.
Rendering with the same amount of polies, but using a precalculated clipped version for the EnvMap was done in 33ms/f on this machine (total 80kTris for the normal Renderworld, inclusive water quad and of course, the clipped quad in the 6*EnvMap Update).
BTW if you would use a relative small EnvMap resolution, it may be possible to use 6 cameras, each one with its own CameraViewport and angle, then create the Cubemap with a single renderworld.