in a recent lecture i just covered reflective materials like glass and water again.
since my last approaches were too complicated i tried to make the water material as easy as possible. sure it is then limited in its features, but it looks ok and has around ~350 instructions. the biggest problem might be, that there won't be any depth fade for intersections with this method. and obviously no volumetric depth which is not possible currently anyway as far as i know. pls comment if i am wrong on this one.
The Material Instance was modified this way
download the normalmap here
this water looks ok with planar reflections as also with a box reflection capture
glas works pretty much the same as water but without the animations. also it has a switch for the use of a glass surface normal.
since glass is not animated, the non planar reflections look a bit meh on it and need to be researched more
the material instance was modified like this
sphere reflection capture
a limited feature set for reflective materials works great. even without the (superexpensive) technique of planar reflections.
if the glass doesnt use normalmaps and bent surfaces, it wouldnt even be necessary to refract.
for large refractive areas use the refraction mode "pixel normal offset" to reduce visual separation of geometry features.