For the Convert Equirectangular to Fisheye node and others, @pbourke suggested:
- the ability to change the order in which rotations are applied (e.g. change between tilt-pan-roll or roll-pan-tilt)
- the ability to add an indefinite number of rotations (e.g. pan-roll-tilt-roll)
We could implement that with a new Rotation data type and accompanying input editor and nodes. These would construct rotations in 3D space.