Wavefront and spot-diagram calculations with respect to an arbitrary propagation axis
Currently, the wavefront data is calculated from the optical path length with a respective x-y position. Similarly the spot diagram creates a pattern with the positions that correspond to the x-y coordinates.
This only makes sense for a propagation axis parallel to the z-axis, but will create deformed spot diagrams for other axes and incorrect wavefront measurements.
To resolve this, additional functionality is needed such as:
- calculation of the distance between propagation axis and the position vector of the ray
- Rotation of these vectors (can probably done with nalgebra)