feat: use grid for surface ordering

[asalzburger]

This feature is in preparation to describe full detectors with grid navigation. It will prepare this with small changes to the current tests:

Currently, in test_surfaces.hpp surfaces for a dummy cylinder barrel and/or endcap disc are generated using:

• barrel: dtuple<darray<scalar, 2>, dvector<transform3>> barrel_description
• endcap: dtuple<darray<scalar, 3>, dvector<transform3>> endcap_description

In a first step, expand the two methods to include also a suitable grid2 implementation, which is created with the correct indices of the surfaces in either barrel or endcap:

• barrel: rphi, z
• endcap: r, phi

Then, write a test, where you check the bin contains the best surface and with a zone check around (the grid should allow you to not only get the index of the bin, but a defined zone around).

[niermann999]

So in the end the functions should return the grids instead of the vector tuples? Should this at some point become a detector description structure used in conjunction with the allocated memory for the surfaces?

[asalzburger]

It should return:

bounds, transform, grid

Where the grid points to the index of the according transform.

[asalzburger]

The overall goal is to change the surface finding in a volume from all (what is happening right now) to grid with a zone.

[niermann999]

Ok, so the binning is not configurable, but should be found automatically from say the detector dimensions, the number of surfaces, and their sizes etc., right? The range for the neighbor search should be fixed?

[asalzburger]

In test_surfaces.hpp you actually know the binning in rphi/z or r/phi, so you do not have to automatically detect it (also for the reading of a detector via csv/json we should rely on the binning to be known.

[asalzburger]

Hi @niermann999 - I decided to work a bit more on this, and created #31 as a first detector, this introduces some grid structure for finding the surfaces in local proximity, seems to work for a start.

[asalzburger]

This is fixed with #31 and some onwards PRs.