I tried blurring reflective texture coords (as emission) and disturbing normals of refraction and glossy in several ways, but I can not see a possible solution rendertime to fake a better HDRI lookup in orthographic. Faking HDRI reflections is easy, make HDRI glossy invisible and “Add Shader” “Glossy Shader” with an “Emission Shader” hooked up to an environment map, possibly using reflected texture coords (can’t remember). Combine this into slot 2 on a “Mix Shader” using “Transparency Shader” in slot 2. If using fresnel, you may want to invert it for backfacing faces (fresnel IOR = 1/IOR, backfacing as fac on a color mix). For fake glass panes with some thickness, you can use normal to darken and give a slight green tint to the rim (looking into rim in real glass lets you see “infinite” reflections due to total internal reflection effect, and the absorption becomes more visible). I wouldn’t bother with true absorption, tint the transparency shader just slightly if anything.
But for othographic, I’m clueless.
Faking refraction (also in perspectivr) I’m not sure is possible. We only have reflected ray (for glossy sim), not refracted ray (for refraction sim). Every time I try something like this it ends up black because it enters the media (same problem as smoothing and bump maps on sharp reflections).
I had some success rotating the env map 180°, then on the incoming based emission environment map, in this order:
Scale X to -1.
Rotate X 180.
Rotate Z 180.
I’m probably doing too much here, but it’s time to hit the sack
Edit: Here is an attempt on faking glass looking up additional transmission and reflection from HDRI:
Effect is additive and will probably brighten if looking through multiple panes. Also, this does nothing for your orthographic problem, which I assumes is the biggest show stopper.