[f3cad84] [SW] Boat on Hara-kiri Harbor not rendering always

[InsanityBringer]

https://imgur.com/a/YpBzJis

A large boat on the Shadow Warrior map Hara-kiri Harbor isn't rendering correctly. The above imgur gallery shows the problem. When you're in the water, the boat renders properly, but when you're on the docks, it doesn't, and if you jump into the boat, the outside world won't render in full.

A couple of the other vehicles seem to have some small issues too. Parts of the forklift on the second level won't render correctly based on the current view angle and its orientation.

EDIT: After further testing, if you start a fresh session and go straight to the map, or load a game, it seems to work. If you came from the prior level, like I did when I first encountered this, I guess it breaks? I wonder if there's some state leaking across level loads... or so I thought, but trying to retrace my steps through both Killing Fields and then Hara-Kiri Harbor, I can't seem to make it happen again. Oh no. Whatever caused this wasn't committed to a savegame I made of the broken scene.

[Graf Zahl]

Looks like a duplicate of https://github.com/ZDoom/Raze/issues/823

That said, I have never been able to reproduce it so I have no idea what might go wrong.

[InsanityBringer]

Hmm, my autosave for the level seems to reliably replicate the problem.. not sure why a save made afterwards doesn't.

https://drive.google.com/file/d/1mou1aA ... drive_link sorry for the google drive link, too big to attach here. Can confirm that it still works if you download the whole thing though

I decided to get my hands dirty and build Raze myself, and even with a completely fresh config and the game built in debug mode, I can still replicate it with that save. I guess worse comes to worse I'm going to have to dig in and see if I can figure out what's going on myself.

EDIT: All I can tell so far is that the sections end up different across the two loaded levels. In the broken scenes, viewing from hopefully the same point on the boat, it eventually enters Section 34 it iterates into Section 206 with 22 lines, but in the normal scene, I watch the bunches added and they're the same until Section 34 comes up, at which point it iterates into Section 205 with 140 lines and ends up making a lot more bunches as a result. I'm really confused..

After working on it for a while, I haven't found the underlying cause yet, but I figure out where the change happens. hw_CreateSections gets called twice when loading a game. The first time from loadMap, second time from SerializeMap. In a good savefile, section line 265 has a partner section of 205. after both calls. But in the bugged save file, it ends up with a partner section of 205 the first time, but 206 the second time around. Guess I gotta dig deeper into the section creation code to figure out what's different between the saves.

[Graf Zahl]

Thanks for the save. That allowed me for the first time to analyze this problem. Turns out I stumbled over other effects of this before, but never was able to find the cause because most of the time it was a transient problem that went away too quickly to check what happened.

This bug already existed in the DOS engine but by sheer dumb luck did not glitch unless a very specific set of conditions was met, and it was one change to the autosave system last year that made the glitch persist when loading an affected savegame.