Incident wave direction vector

[inzhevatkin]

It would be interesting to add an arrow of the incident wave to the 3D visualizer. It direction coincides with the vector prop.

[myurkin]

This is a first step for potential visualization of the incident beam. But it is not clear (even conceptually) how this general problem should be solved (consider, e.g., some complex Bessel beam).

So for now, it is more an illustration of the interplay of -orient and -prop options. And in line with this, I recommend to distinguish two reference frames (particle and laboratory ones). If non-trivial -orient is used, current axes (bound to a particle) should be named X', Y', Z' (and probably have different color), while the laboratory axes X,Y,Z can be the same as now. When default orientation is used, a single frame X,Y,Z seems to be sufficient.

[myurkin]

In future, we can even think about using the 3D image as a control of both particle orientation and propagation direction. So rotating the particle with mouse will change the -orient angles, while moving the beam-propagation arrow (which can be limited to some sphere around the particle), will change the -prop values. And we can extend this to moving the beam center as well (for beams other than plane wave).