Volume refraction

As we know, for example air IOR is 1.000293, that is very small, but if you have a very hot air and cold air close of each other, that will make a big distortion effect. (camp fire for example) If you wanna render that, I think you should be able to.

If we had in Cycles render engine the IOR setting for the volume shaders, that would for example allow us to render realistic mirages, heat distortions from fire, and all of those cool gas or liquid volume IOR related things (salt water in clean water) that currently are possible only by faking it.

You should be able to disable the effect completely by leaving the IOR value of your volume shader to 1.