How to close polygon/add points to last boundary?

[rsignell-usgs]

I've got corner 4 points and I can generate a mesh, but how can I add more points to the "4th" boundary (indicated in the figure below by the dashed line I drew in a paint program):

@jlstevens Is there a way to "complete the polygon" or something so that "last" side gets drawn?

[rsignell-usgs]

@jlstevens post-holiday ping. 😸

[jlstevens]

@rsignell-usgs Happy New Year! I'll try to have a look at this tomorrow.

[rsignell-usgs]

@jlstevens I understand you guys had a big deadline, so no rush, but I still haven't been able to figure this out, so help requested! This is blocker for me creating a realistic grid for ROMS, which of course is the point of this tool!

[jlstevens]

I understand you guys had a big deadline...

Yup! That ended yesterday so now I have more time.

This is blocker for me creating a realistic grid for ROMS, which of course is the point of this tool!

Understood - I'll get back to you later today.

[jlstevens]

After installing from conda-forge, I drew an approximate version of the shape above and meshed it:

Here is what the boundary looks like with the mesh hidden:

Would this not be the mesh topology you are trying to generate above? Can you not extend what you drew with an extra node and set the polarity (or insert a node into the last segment and rearrange)?

[rsignell-usgs]

@jlstevens, okay, I see this is not a blocker, that I can continue to add more points along that "last boundary".

I guess I was confused because the way I usually operate is to draw a box, and then go and start adding points to each side. And I didn't see how to add a point to the side that wasn't drawn. So it would be nice to draw that side. It would make it more intuitive, IMHO. Thanks for looking at this.

[jlstevens]

okay, I see this is not a blocker...

Glad to hear it!

When working on hologridgen, I think we discussed whether we should keep the drawn polygon open (implicit last edge) or closed and we opted for the former. This issue raises one problem with the implicit approach, namely that you can't add a node in the middle of the last edge if it not drawn (due to being implicit).

I did have an earlier prototype which did allow optional closing of the polygon but in the end, I stripped that out to simplify things. That code is probably in the git history somewhere and I'm sure I could resurrect it (i.e add a checkbox to optionally close the polygon, allowing people to choose their preference for how they work). I estimate it would be a day of work to bring that back, test it and make it robust (I seem to remember that the prototype didn't always work the way I wanted).