# Sonic and Sega Retro Message Board: compression algorithms? - Sonic and Sega Retro Message Board

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## compression algorithms? is there a logic to discover?

### #1Weird Person    Posted 13 August 2005 - 09:27 PM

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Ok, First, I will give good news over Sonic 3D Blast, I found all (well, looks all.) the pointers for the data to all levels. They are grouped in ten pointers per offset.
(when I say offset, I mean where the pointers are, not where the pointers are pointing.)

\$1AB62 : Green Grove Act 1 Pointers.
\$1AB8C : Green Grove Act 2 Ponteirs.
\$1ABB6 : Green Grove Act 3 Pointers.
\$1AC5E : Rusty Ruin Act 1 Pointers.
\$1AC34 : Rusty Ruin Act 2 Pointers.
\$1AC88 : Rusty Ruin Act 3 Pointers.
\$1AE02 : Spring Stadium Act 3 Pointers.
\$1ACB2 : Diamond Dust Act 1 Pointers.
\$1ACDC : Diamond Dust Act 2 Pointers.
\$1AD06 : Diamond Dust Act 3 Pointers.
\$1AD5A : Volcano Valley Act 1 Pointers.
\$1AD30 : Volcano Valley Act 2 Pointers.
\$1AD84 : Volcano Valley Act 3 Pointers.
\$1ABE0 : Gene Gadget Act 1 Pointers.
\$1AC0A : Gene Gadget Act 2 Pointers.
\$1AE2C : Gene Gadget Act 3 Pointers.
\$1AE80 : Panic Puppet Act 1 Pointers.
\$1AE56 : Panic Puppet Act 2 Pointers.
\$1AEAA : Panic Puppet Act 3 Pointers.
\$1AED4 : The Final Fight Pointers.

As I said, these offsets are related to a group of ten pointers, each pointer means:

1st Pointer: Object Placement , Compressed?
2nd Pointer: Collision Level Layout / Sonic Start Position (?)
3rd Pointer: B Plane Mappings.
4th Pointer: Graphics.
5th Pointer: A Plane Mappings.
6th Pointer: NFC.
7th Pointer: Graphical Level Layout (?)
8th Pointer: NFC.
9th Pointer: Collision Level Layout / Sonic Start Position (?)
10th Pointer: NFC.

The First pointer I'm completely sure they are related to the object placement. Swap the pointers of Green Grove and Volcano Valley, Rusty Ruin and Gene Gadget... and you will get the objects of the others levels swapped. (interesting, they are not glitched, the Badniks Graphics are loaded as well. only the pallete is wrong.)

But while trying to replace the objects, I always get the shitty screen "C 0 |\| G R 4 T |_| |_ 4 T | 0 |\| Z! u fuond teh secret screan!". The unique explanation I get to this is the Object Placement data is also compressed. Somebody knows how to easily discover compression algorithms? my hacking techniques are really stupid, and I don't want disassembly the whole game for just discover a decompression algorithm.

(I not use corruption, but they sound stupid [at least to me.], ex: I look at the Adress registers to see if I find a pointer or something like that. sound stupid no?)
This post has been edited by Weird Person: 18 September 2005 - 07:18 PM

### #2LOst  Posted 13 August 2005 - 10:29 PM

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Good job on finding the pointers. I tried them out and it was fun.

But I am too lazy to look into the format of the objects right now.

EDIT: Remember that if the object postions are compressed in the ROM, they must be uncompressed to RAM, so you can find the format by tracking them down in the RAM.
This post has been edited by LOst: 13 August 2005 - 10:33 PM

### #3Weird Person  Posted 13 August 2005 - 10:50 PM

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I have also re-researched the pointers, the Second definitely isn't any sort of mappings, it's something different, I consider it NFC.

The 3rd looks the B Plane Mappings (Basically this means "the floor mappings"), the 4th looks like the graphics and the 5th looks like the A Plane Mappings. the others are still NFC. (Mappings for everthing that's not floor, except the sprites.)

more answers? corrections? criticizens? anything else?

### #4LOst  Posted 13 August 2005 - 11:02 PM

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Second pointer holds Sonic's startup position and probably something more. I guess.

### #5Weird Person  Posted 13 August 2005 - 11:28 PM

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this is not related to the pointers, but I found this interesting:

seeing the level (Green Grove Act 1) with A plane.

seeing the level (Green Grove Act 1) without A plane.

Interesting, there are a lot of places viewable if you hide A Plane (use DebuGens to do it.), but not walkable. A Plane is used to fix the level broken tiles and also hide cutten parts of levels.

I know in the second picture the ring numbers is incorrect (not match with the first picture), but the picture is true, I just don't want take a screenshot with Sonic in its waiting animation, so I walked a little and back to that spot.

### #6Lostgame  Posted 13 August 2005 - 11:31 PM

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What you should do is get those savestates from Sonicology that have the collision disabled and disable the A plane. It'd be interesting.

### #7Weird Person  Posted 13 August 2005 - 11:40 PM

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I Don't like navigate in Sonicology with Netscape. Those Floating Menus are showed by half.
(they are show at the left, not in the right. they are showed in the Right with M\$ Internet Shit, but I really don't like use IE. Netscape tabs make navigation a lot easier and more confortable.)
And also, in what section the savestates are? They are not in the "downloads" section and also , most of the menus aren't viewable.

And when you get promoted to a techie? I was out by a big time... did I miss something important?

### #8Guess Who  Posted 13 August 2005 - 11:48 PM

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He made a hex editor, made a few guides, and did a helluva lot of Chaotix work. That's how. :P

Good job on finding those pointers, it's a shame nobody hacks S3D.

Also, on the first page of Sonicology, there is a thing on the right to navigate with, or you can click on any of the links on the left without choosing a menu option. Also, doesn't Netscape 8 have a IE option, to browse IE style?

### #9Weird Person  Posted 13 August 2005 - 11:58 PM

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guess_who, on Aug 13 2005, 08:48 PM, said:

Also, on the first page of Sonicology, there is a thing on the right to navigate with, or you can click on any of the links on the left without choosing a menu option. Also, doesn't Netscape 8 have a IE option, to browse IE style?

My version is American 7.2 (the Brazilian version is very shitty if you compare with the American, -2 points from Netscape for not do a good browser to Brasil.) . I'll probably download the lastest later or Buy a CD, I hate download heavy files with DialUp Connection.

Can somebody give me a hand to find the download link? in what section the savestates are?

### #10Tweaker  Posted 14 August 2005 - 12:13 AM

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guess_who, on Aug 14 2005, 12:48 AM, said:

He made a hex editor, made a few guides, and did a helluva lot of Chaotix work. That's how. :P

...and cracked an art format (Spinball) and a compression format (Crackers).

Anyway, nice stuff. You're making S3D quite editable to us. We know where the data is now... So we can work on cracking formats.
This post has been edited by Tweaker: 14 August 2005 - 12:14 AM

### #11ICEknight  Posted 14 August 2005 - 01:01 AM

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Tweaker, on Aug 14 2005, 12:13 AM, said:

...and cracked an art format (Spinball)

What? Where? etc

### #12drx  Posted 14 August 2005 - 05:24 AM

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eh?

### #13Lostgame  Posted 14 August 2005 - 11:30 AM

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Quote

And when you get promoted to a techie? I was out by a big time... did I miss something important?

Quote

He made a hex editor, made a few guides, and did a helluva lot of Chaotix work. That's how.

I did more Crackers work than Chaotix work, but yeah, that's mainly it.

Quote

and a compression format (Crackers).

Actually, Tweaker, that's an art format, similar to Nemesis, but not Nemesis at all.

No, I didn't crack the spinball format, just the Crackers format, and shh, Tweaker, you're not supposed to tell anyone until I'm ready.

I've been hacking spinball, but I haven't looked at the art...

I've also been hacking 3D blast, but only a limited amount of things. I am very happy that other people are checking these things out, because Sonic 2 is getting a little overhacked, and S3K is just a pain.

Heck, the spinball format might be the same one as used in Crackers... *runs off to look*

EDIT: Oh, yeah, my palette editor probably helped a little, too. And maybe my VB programming guide...
This post has been edited by lostgame: 14 August 2005 - 11:31 AM

### #14ICEknight  Posted 14 August 2005 - 11:41 AM

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lostgame, on Aug 14 2005, 11:30 AM, said:

Heck, the spinball format might be the same one as used in Crackers... *runs off to look*

Well, I've always said that either it's the same format or a quite similar one. Either way, if the Chaotix graphics were cracked it shouldn't be too difficult to crack these...

### #15Tweaker  Posted 14 August 2005 - 03:09 PM

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lostgame, on Aug 14 2005, 12:30 PM, said:

Quote

And when you get promoted to a techie? I was out by a big time... did I miss something important?

Quote

He made a hex editor, made a few guides, and did a helluva lot of Chaotix work. That's how.

I did more Crackers work than Chaotix work, but yeah, that's mainly it.

Quote

and a compression format (Crackers).

Actually, Tweaker, that's an art format, similar to Nemesis, but not Nemesis at all.

No, I didn't crack the spinball format, just the Crackers format, and shh, Tweaker, you're not supposed to tell anyone until I'm ready.

I've been hacking spinball, but I haven't looked at the art...

I've also been hacking 3D blast, but only a limited amount of things. I am very happy that other people are checking these things out, because Sonic 2 is getting a little overhacked, and S3K is just a pain.

Heck, the spinball format might be the same one as used in Crackers... *runs off to look*

EDIT: Oh, yeah, my palette editor probably helped a little, too. And maybe my VB programming guide...

Nemesis isn't an art format... It's a compression algorithm primarily used for art. If this new compression is similar to to Nemesis, it must be another variation of LZ compression.

ICEknight has a point... Spinball may use a buffered art format like in Chaotix. Guess it's always worth a shot.

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