Draft riverspace delineation

[cforgaci]

@fnattino I drafted the riverspace delineation starting from this approach. As an additional step, I subtracted the first line of buildings form ther resulting isovist. This creates a more accurate first line:

However, it does not solve some less accurate boundary details, both in the back and in the front of buildings:

Whenever the river is underground, the river centreline could be used as a fallback option for viewpoints:

The overall delineation is ready for review. If you agree, we can fix the above details within the CRiSp repo.

[fnattino]

Amazing @cforgaci , seems to be working well! We can definitely merge it and refine details when porting to CRiSp.

It can probably be improved performance-wise, as I think creating many sf instances (e.g. for each rays) adds quite some overhead.

Maybe we can also think whether such visibility analisis could be implemented as a separate package to facilitate reuse in other contexts as well?

[cforgaci]

Thanks @fnattino for the review. I will then merge and create a module in CRiSp based on this prototype.

It can probably be improved performance-wise, as I think creating many sf instances (e.g. for each rays) adds quite some overhead.

I will create an issue on this in CRiSp once the module is created.

Maybe we can also think whether such visibility analisis could be implemented as a separate package to facilitate reuse in other contexts as well?

Good idea! I will also draft a package on this and we can remove the module from CRiSp once the package is functional.