PETKA: Broken pathfinding

[Tkachov]

In ScummVM heroes sometimes choose a weird route when you ask them to walk somewhere.

Video demonstration: ​https://youtu.be/6fwc0zaqSTE (first 54 seconds are in the original game, the rest is in ScummVM).

There are no "Walk bug: Point doesn’t belong to any convex" messages during that. They just happen to select a strange path instead of a more "natural" one, while in the original game they select the "natural" one.

Attachments:

attachment:petka1.s16​	ScummVM save file on the shown screen
attachment:save14.dat​	Original game save file

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ScummVM 2.3.0git11899-g3fb4d67b4e (Jan 16 2021 05:21:57)
Windows 10 version 20H2 64-bit
Petka 1.0.0.1 aka Red Comrades 1

To reproduce:

• load the save file;
• select 'Walk' cursor (right click, then left click on the purple silhouette icon);
• click somewhere (it seems if you alternate between above and below the fountain you could achieve this weird behaviour);
• <you would see the character go somewhat indirectly in ScummVM, but won't see that in the original game>.

[Tkachov]

Added the region render to this ticket:

Red line shows the outline and green ones show the inner polygons. I've heard characters can only walk from one polygon to the other through the their common edge, but I have no proof of that. Anyway, it's clear that character shouldn't go behind the fountain, but on the video you can see her doing it.

[whiterandrek]

Thanks
The problem is in that somewhere in the code it doesn’t match to dissasemly and it is very hard to find this glitchy part