Just a small tweak, the shader should also render when inside the rift. This also could be applied to the fractures.

Suggested here:
Azanor/thaumcraft-beta#1732

Interesting workaround presented there - it would work well for the shaders for sure, although I will probably leave it the way it is for the case when shaders are disabled.

Cosmetic suggestions, which relate to rendering:

Rift spawning animation:
Right now rifts just appear out of nowhere. They need a bit of more blast, with them ripping apart a tear into the fabric of reality. Maybe use the same animation that happens when the rift collapses but in reverse.