- A reflective surface (read: water) must be approximately flat to be correct. This is just how the algorithm works. (If you want to see why a non-flat surface fails, try to draw a camera position opposite the reflection plane and trace rays through this "reflection camera". Draw reflected objects that are close and far from the water and then observe the parallax error you get if the reflection plane curves.)
- We need one "water camera" for each flat reflection plane. You can't just statically offset when we have multiple elevations. (When drawing your diagrams, note how an elevation change causes a change in reflected angle, not just an offset.)
X-Plane tries to get around the non-flat water problem by picking little bits of the water that are flat (and seem useful) and using them to define reflections. This algorithm will always have problems, but at least it can be tuned.
Now there are also some things that we can fix with the water:
- The math in beta 18 is simply wrong, something that will be fixed in beta 19.
- The ocean is built from polygons that are too large; this introduces approximation errors when we try to pick "a little bit" of water to use to figure out our reflection plane.