Feature: Add DSEA projection

[felixpalmer]

Overview

This PR is stacked on top of the root PR: OSGeo#4758 - please see there before reviewing

Adds support for the DSEA projection (the dodecahedral equivalent of ISEA), along with a number of output net configurations. The DSEA projection is used in https://a5geo.org/ and has lower deformation than more widely used ISEA projection.

Change list

• Add configuration files for implementing DSEA: decakis_dodecahedron.h
• Add configurations for output nets: nets/dsea/***.h
• Register new projection
• Include in test render scripts

Example renders DSEA

[jerstlouis]

@felixpalmer Would it be a good time to rebase/update these extra features on top of the main polyhedral PR while we wait for the workflows to be approved? It would help to see how easy it is to add these extra polyhedra.

I'm curious about how hard it would be to add the Truncated Icosahedron in particular (TISEA / TIVEA) :)

[felixpalmer]

@jerstlouis well, DSEA & ISEA have already been moved into the main PR, so we can close these extra ones. IVEA & TISEA I don't want to tackle right now as it'll complicate the already large PR.

Could you confirm everything looks good in that main PR now? I can then do a pass and update the description and docs and then we can mark it as ready for reivew

Spoilers though, I have prototyped TISEA ;)

[felixpalmer]

Closing as root PR includes DSEA

[jerstlouis]

@felixpalmer

Could you confirm everything looks good in that main PR now?

I haven't looked at every single line or tested compiling or running it myself, but it does all look very good.

One thing: since you've demonstrated parity with the existing ISEA projection, could we maybe just replace isea instead of adding isea2?

Especially if you're able to test the specific issue in OSGeo#4389 with gdalwarp and confirm that this generalized ISEA implementation addresses those issues and you could add "(fixes OSGeo#4389)" to the PR description.

Also I still hope to do a future PR with the improved formulas possibly avoiding trigonometry and achieving greater precision (and at that point we can then change the round-trip tolerance from 0.2 mm to 23 nanometers).

(also in your current description you have 1 nm -- I would remove that, as the current tests don't demonstrate that, and I don't think that is true at the more tricky locations near the vertices and edges).

Maybe also remove the mentions of PR 2 and 3 that are now closed from the description?

[jerstlouis]

@felixpalmer Very cool for the TISEA prototype, but the face numbering is not quite right yet :) (Compared to Figure 4).

[felixpalmer]

not quite right yet :)

😆 close enough for now