SCUMM: Loom (TG16) - Visual glitches with the forge bricks and actors

[dwatteau]

This is with today's ScummVM 2.6.0git4753-g87f2f5c196f, with my original Japanese version of Loom TurboGrafx-16/PC-Engine.

If you go to the forge with Bobbin's apparence:

1. First glitch: The guard will go to the tower on the right, speak a bit, and then leave. When he leaves, he'll "walk through" the tower bricks for a couple of seconds.
2. Second glitch: go to the grid, use the E-C-E-D (open) draft on it, and try entering the forge. Both Bobbin and the guard will glitch with the bricks there, when entering and leaving the forge.

(A quick way to go there is to start the game, go to the main tent and open the egg, then "room 34" in the ScummVM debugger, look at the sleeping boy, then go the right *without* taking his apparence).

I don't have an original PC-Engine console to see if the original interpreter has the same bug.

[dwatteau]

It's not the exact same version (Japanese vs. English) and not the exact same action, but the following video appears to use the original interpreter and doesn't have the glitch:

​https://www.youtube.com/watch?v=P-tUJVGprr0&t=3638

[dwatteau]

Loading this savegame will NOT trigger the bug, you need to follow the instructions above

[dwatteau]

So, I played my game in OpenEmu (which uses Mednafen 1.16.1) and there's no glitch there either.

It doesn't appear to be a recent ScummVM regression, because I could also reproduce this behavior with ScummVM 2.2.0 (2020) and ScummVM 1.4.0 (2011).

However, here's a funny thing: if you follow my procedure above, you'll see the glitch. If you save the game just before the guard goes back to the forge, you'll still see the glitch. But if you *load* that savegame, the glitch is gone, most of the time (see the attached savegame, made with ScummVM 1.4.0).

[dwatteau]

Glitch after untwisting the stairs

[dwatteau]

Glitch after untwisting the stairs

[dwatteau]

And here's another glitch:

1. Start the game
2. Go to the main tent, grab the distaff and open the egg
3. Type room 33 in the ScummVM debugger
4. Learn the missing drafts with drafts learn
5. Go back to the cave and then back to the stairs (to make sure that the SCUMM room is properly initialized)
6. Untwist the stairs (use the drafts command and type the reverse of the Twisting line if necessary)
7. Go to the right: Bobbin's head will glitch a tiny bit in the clouds, and more importantly he'll glitch through the column in the middle of the stairs (see the screenshot above).

(The loom-pce-jp.s14 savegame puts you at the end of step 4.)

It looks like the glitch only happens right after the stairs untwist, i.e. if you go back to the stairs once you went to the forge, it won't glitch anymore.

I could reproduce this glitch with ScummVM 1.4.0, too.