Debugging Rivers

[Undead Martyr]

After trying to add several rivers in and around northern Italy, I find that the map crashes with no map.rwm generated when I try to start a campaign (no load bar, just ctd.) I am fairly confident that it's something to do with the rivers, since a blank map_features solves the crash, but I was wondering how much I had to pare down to solve the issue; additionally, are there any other pitfalls, like having a settlement next to a river or with two crossings in close (non-adjacent) proximity?

I've attached the map .zip.

[Gigantus]

Here is your issue, a 'double' pixel:

[Undead Martyr]

Thank you, I found and fixed by deleting and redoing the map_features file and have made considerable changes, including functional rivers. Unfortunately I am now crashing trying to do land bridges around the Aegean and elsewhere; are there any particular rules re- diagonal land bridges or having to terminate on a particular ground_type or map_heights, e.g. does it matter if the land bridge goes over water or ends on water/impossible terrain etc. The site's search isn't the best, and neither the wiki nor a casual perusal of threads seems to have the answer.

Currently debugging, will update on progress as it comes.

[Gigantus]

The land bridge can only be one pixel wide and must be straight. Can't be next to other map_feature pixels or settlements\ports.

[Undead Martyr]

What about the terminus? Does it need to be 100% on land?

[Gigantus]

That is not a requirement, you can have the land bridge completely in water - it may however not be accessible. The number of pixels used needs to be in multiple of 2, else it will not display\work correctly.

[Undead Martyr]

When you say "won't work correctly" do you mean bad textures or a no map.rwm CTD? Whatever it is, it's definitely one of the land bridges, and I'm sure it has to do with some finicky bit of the code not liking the beautiful mess that is the many Aegean Islands.... although it was actually still crashing even with some of the simple landbridges, like the Strait of Messina or the river crossings. Hence my current suspicion that it may be the odd-numbered landbridges that are causing the problem.

[Gigantus]

A three pixel bridge will only display as two pixels, being the strat models display length. Hence only even number of pixels should be used. Diagonal connecting pixels may cause a crash, eg two independent bridges close together.
'...like the Strait of Messina or the river crossings'? I am assuming you mean rivers created by using map_heights, not the map_features type?

You can check for interference by overlaying map_regions and map_features to see if ports and\or settlements pixel are covered by feature pixels. In case of the bridge (and volcano\cliffs) there needs to be one pixel space between them.

[Undead Martyr]

I've been using Geomod to test proximity. Length seemed to have been one of the main culprits, but based on trial and error I do think there is a requirement tied to ground_types and/or map_heights that 1) there be at least two ground pixels underneath the terminus and/or 2 that it doesn't cross more than one piece of land, not entirely sure which. Thanks for your help, I figure I'm just going to have to add them one at a time and verify after each one. That's what I get for trying to rush things I guess!

Progress so far on the Aegean:

Spoiler Alert, click show to read: 

[Gigantus]

Baby steps is usually a good way to proceed if you run into issues like this - it will show you exactly where the problem is (if it shows up again).

And making backups every time it worked.