The Supreme Topic of 'Other' Knowledge.

As far as I know, you can't knock monitors off their perch in S3K, unlike 1-3, right? If so, could someone explain this:

http://www.youtube.com/watch?v=qzw-3jtcbQE

 

Pretty sure you can knock down floating monitors in all the Mega Drive games, can't you? I haven't played S3&K in a long time now, but I remember being able to do it in AIZ2 with the Fire Shield in a tree near the end of the level. I know the memory can sometimes cheat, though, so I could be wrong.

Assuming I'm right, then I guess what happens here is that neither Tails nor the monitor register the platform any more as it's not on screen - thus Tails jumps right through it and knocks the monitor down. As to quite how/why that can happen, someone more technical will need to get involved (and probably point out flaws in my guesswork while they're at it, heh = P).

 

For some reason, S&K only destroys the monitor if it's right side up; there's actually a check in the code that does this:

Code (ASM):

1. ; loc_1003A:
2. .checkfall:
3.         ; This check is responsible for S&K's monitors not falling if hit from below (but only in regular gravity. See below)
4.         btst    #1,status(a1)               ; Is the monitor upside down (different way of checking)?
5.         beq.s   .checkdestroy               ; If not, branch

So, yeah, if the monitor's upside down, it just falls.

 

Sonic 3 and Knuckles has monitor behaviour whereby hitting a monitor from underneath causes it to break, not be knocked down. This is different to Sonic 1, 2 and 3 (alone) where the monitor will fall to the ground. However, this change does not apply to upside down monitors if they are hit by Tails, where they fall to the ground like the original games. The behaviour was changed between Sonic 3 and Sonic (3) and Knuckles.

In the video shown, Tails jumps through the platform as it is off screen (and objects are unloaded if they are off screen to save memory), but manages to hit the underside of the monitor. This causes the monitor to fall down (or up, as the case is for switched gravity). The timing on this is so small, and yet somehow the person managed to have it occur in said video, so I am surprised.

McAleeCh, your recollection of the fire monitor toward the end of Angel Island Zone 1 falling down from the tree by being knocked down is correct. This does happen in Sonic 3 (Alone) but not Sonic (3) and Knuckles.

EDIT: Semi-ninja'd by Clownacy

 

But... S3K only unloads object when they're offscreen to the left or right, not top or bottom?

 

No, it unloads them both horizontally and vertically in Sonic 3 and Knuckles. If you pull off the screen wrapping glitch with the camera (duck, let go of down and immediately jump afterwards, on a level that wraps), you can walk through objects that are off screen, as they have unloaded.

 

...Really? That floating platform, Obj_DEZFloatingPlatform, uses Sprite_OnScreen_Test2 to unload itself, and that only checks Camera_X_pos_coarse_back. What's more, if the platform unloaded, then why didn't the monitor? The same object uses SolidObjectFull to collide, but I can't see anything that looks like an onscreen check in there, not even in the code it branches to.

 

I don't know how that specific object works on a coding level; only my experience with it in game and using it in my own level layouts. I could be wrong, of course, but what I said previously appears to be what is happening, at least to me. If it's not, then I would be intrigued to know what actually is happening with that platform.

 

Huh, guess I'm just rather lucky then. Guess the game developers weren't expecting anyone to be able to reach through those platforms, eh? Can't see anywhere else where you might be able to knock monitors down.

 

It's not just a Tails thing. Sonic can knock them "down" (up) (?!) in reverse gravity too, but he has to be gentle about it: the knock-down monitor behaviour pushes the monitor up briefly before it falls, but this isn't fixed for reverse gravity, so bumping it from above causes it to start moving upwards immediately. If you're rolling, this usually means you end up breaking it before you can see the full effects. You probably need debug mode to prove this, as far as I know, since there are no floating monitors in DEZ2, and Sonic (usually) lacks 2P Tails' ability to abuse the screen limits, so it's fairly academic, but note that you can't bulldoze monitors sideways during the reverse gravity sections like you can upright in S&K (due to the added code Clownacy noted).

Here's some discussion about it from 2011, before I restored the S1-3 behaviour to Sonic 3 Complete, if anyone's interested. I still don't really know why S&K's code ended up the way it is, but it's very strange and inconsistent (though it's certainly neither the first nor the last thing that's turned out to be so).

"Everyone knows" (see screen wrap glitch) that object collision doesn't happen vertically offscreen, but here, the monitor is further off screen than the platform, and it appears that the platform collision is skipped while the monitor collision is processed. You can go and prove that monitors behave differently in debug mode, too: go to ICZ1, where you'd normally screen wrap through a pillar, and place a debug monitor before it. Trigger the wrap glitch, then spin dash forwards, noting that you will break the monitor but pass through the solid pillar. I believe this is the code (early in SolidObjectFull) that's responsible in this case:

Code (ASM):

1.  
2.         tst.b   4(a1)
3.         bpl.w   locret_1DCB4
4.  

So indeed, the objects are still loaded, and are mostly only unloaded by their X position, but SolidObjectFull won't process something that doesn't have its on-screen bit set (4(aN) bit 7). Monitor collision involves no such check.

EDIT: I am saying impudence to you - the above only applies to player 2 (so it's probably just as relevant to the video posted here, but less so to screen wrapping). I'm placing my bets on loc_1DF88 being the culprit there. Pretty much the same principle though - SolidObjectFull checking the visible bit before doing its space magic.

 

I don't know if some technical wizard can do anything with these pics from this auction of Flickies island but this cover and what not is better than the one on the wiki and as much as I love this site, I'm not forking sixty quid just for wiki scans.

http://m.ebay.co.uk/itm/Sonic-3D-Blast-Sega-Mega-Drive-Super-Gamboy-Korean-Release-CIB-Hard-To-Find-/111777059511?nav=SEARCH

 

waitwaitwaitwaitwait, back up a little there. What's Samsung gotta do with all this? @.@

 

If I recall correctly, the Republic of Korea had a ban on importing Japanese goods due to their histories, until 2004. As a result, the companies merely outsourced their production to Korean developers (Nintendo went with Hyundai, releasing the NES as the Comboy there).

 

Come on lad,

we have these big fancy wikis, and they're quite good.

 

I spy with my little eye
http://retrocdn.net/index.php?title=File%3AMegaDriveFan_JP_19910701_f.pdf&page=5
A building from Sparkling Zone, in that old Sonic manga.

 

Something I legit did not realize until today and haven't actually seen documented anywhere:

If you let the clock run out on Knuckles' final battle in Sky Sanctuary (S&K/S3K), you'll notice that island is very slowly sinking, going down a pixel's height every few seconds. If you can survive the boss fights for around 9 minutes, you'll see that most of the island has sunk below the stage floor!

 

Oh wow. I've not noticed this before either. The amount of detail in that game is stunning.

 

Then there's some things that show it was a tad rushed. Like Tails at the End of Level tally with Sonic. Before he shifts back to his standing sprite, the victory pose glitches slightly:




Sorry for the large overscan. PAL consoles, different resolution.