There are two NiGHTS-related music tracks on Sonic Adventure GD-ROM. One is called NIGHTS_A, which is the a capella cover of “Dreams Dreams”. The other is called NIGHTS_S, which is another mix of “Dreams Dreams” called “Sweet Mix in the Holy Night”. The A version is the one you hear with the Christmas 99 DLC when you touch any of the Christmas trees, the other one you don’t get to hear ingame normally but there’s a bit more to it than the song being unused.

A while back I found out that the S version is actually referenced in the Christmas 99 DLC, but the object that plays the song never loads because it has the “wrong” level ID, and the one that plays the A version gets loaded in its place because it has the “right” level ID. In the game’s internal level list Station Square has the ID of 26, while the objects playing the S version use 27 and 28. It’s pretty clear that at some point in development the game had the day, evening and night versions of Station Square use different internal IDs, even though the final game only uses 26. Even the “Easy Menu” in SADX Preview prototype refers to 27 and 28 as evening and night versions respectively.

The XMAS99 DLC places four Christmas trees around Station Square. If you look at its object placement (which you can do with the DLC Tool in SA Tools), you can see that for each of those trees there are “evening” and “night” versions that are supposed to load in levels 27 and 28. One of the parameters in those objects is the music track ID to play. The regular “day” trees use 68, which corresponds to NIGHTS_A, but some of the “evening” and “night” trees use 70, which is NIGHTS_S. For example, this one in the City Hall area:

While it is trivial to switch the IDs around and make these trees play the S version at all times, I don’t know of a way to restore the seemingly intended functionality with the trees playing different songs at different times of day. The old Dreamcast DLCs mod for SADX had this behavior hardcoded, but the new mod loads objects in a way a bit more similar to the Dreamcast version, so it doesn’t work for the same reason it doesn’t work in the original. I’ll probably just make this tree play the S version because why not?

There’s one more interesting thing about this DLC and unused NiGHTS songs in SA1. We’ve seen both music IDs 68 and 70 used, but what about 69? While it isn’t referenced in the DLC, we know from the PC version that there was supposed to be yet another NiGHTS song called NIGHTS_K, which would be using this ID. As no version of the game has this file, we can’t say for sure what was supposed to be. The Kids version of “Dreams, Dreams”? The Karaoke version? “Know Thyself!” maybe? To me, the Karaoke version makes the most sense, but we can only guess.

The updated DLCs mod for SADX PC is coming along well. I rewrote the entire mod from scratch and made it work in a way that resembles the functionality used in the original game. It’s also partially compatible with original data from SA1 DLC files provided that you convert it first using the DLC tool and replace some of the stuff that isn’t supported by the PC version, such as MLT soundbanks. Model and metadata files are fully compatible. So in the future if you decide to make a custom DLC for the Dreamcast version, you will be able to prototype it in SADX PC first using the new DLC mod, which makes object placement easier.

I’ve been wondering for a long time how SA1 draws its “Now Saving” and DLC timer strings. Apart from being italicized (and looking glitchy with letters overlapping each other) the font looks thicker than the font used in debug menus, and the 0 character looks different, and I started thinking it was a different font altogether.

Today Exant figured it out, and the answer to all this is just… Weird. It’s the same font, but there’s code that… replaces the zeroes in text with the letter O. The rest is a lot more believable: the font looks thicker because the letters are stretched horizontally, and the italics are done by offsetting the top right X coordinate of the letter’s rectangle.

I’ll be updating DC Conversion and the DLCs mod to improve the look of the font, though I also want to rework the DLCs mod from the ground up. I want to make it possible to load the data produced by the SA1 DLC tool I made for SA Tools. That way you’ll be able to convert DLCs between SA1 and SADX. There’s some fundamental incompatibility with sounds and music, which I won’t be able to resolve in a while, so it will probably be only partially compatible, but anyway I’ll save that for another post.

A write-up will be available later

I’m working on a tool to extract SA1 Dreamcast DLC files. While we’ve already gotten most of their data extracted and the content is recreated in the Dreamcast DLCs mod for SADX, I want to make a tool to work with DLC files directly and get everything out – item layout, text data, textures etc. I also want to make it possible to modify and rebuild DLC files.

Now why this is included after some text strings, I’m not sure. Some DLCs just have stuff inserted that makes little sense. Random garbage from memory? Some kind of weird anti-tamper measure? Who knows. Maybe I’ll figure it out eventually.

I found this unreferenced flowers model in leaked SADX X360 symbols. It uses the Dreamcast version’s CHAO.PVM and is located in the same region as objects used in the Chao Race on DC, such as the watering can or the trumpet. What is it? Some kind of unused Chao Race object or toy? No idea.

If you want to have a look at this model, you can find it in AL_MAIN.BIN (SA1 v1.005) at 14E10C.

This post documents my experience with Sonic Adventure NB files and my attempts to reverse engineer the format.

NB is some kind of container format for models and animations. It’s different from container formats used in the Katana SDK, and I haven’t seen any other games use it. There are only two NB files in Sonic Adventure/DX that are used in all versions of the game: E101R.NB and EROBO.NB. As you may guess from their names, they contain models and animations for ZERO and E-101R MK II boss fights. A lot of stuff in these NB files can be found elsewhere in the game – for example, Zero’s model and animations also exist in the main binary in the 2004 version of SADX, and E101R has a cutscene model that can be ripped easily. But NB files also contain miscellaneous models for things used in these fights, such as explosions, projectiles and electric barriers, as well as some unique boss animations.

On the Gamecube the NB files are byteswapped and called E101R_GC.NB and EROBO_GC.NB, but in the PC version they are Little Endian despite the “_GC” in the filenames. Apart from Endianness the format itself is the same between all versions, and files from the Dreamcast version will work with the PC version if you simply rename them.

The NB file is composed of binary sections preceded by an 8-byte header. A section can contain models, motions or shape motions (the NB files in SA1/SADX do not contain shape motions, but I found some shape motion loading code associated with one of the section types). Each section is divided into subsections, which have their own headers and contain various types of data. For models it’s vertices, normals, materials, meshsets, UVs, model and object structures. For animations it’s rotations, positions, motion data structures and finally the motion structure itself.

So first I wanted to extract models and animations from NB files. I started with the program called SplitNB in SA Tools, which was already capable of splitting out individual binary sections from the NB file. Getting the models out of those sections was easy because the root model is always at the end of the file, so just loading a model at its address got the whole model hierarchy covered. Animations were a lot more involved, since the motion at the end of the file wouldn’t load without modifications. After a few attempts I managed to reconstruct the full animation from those individual subsections, and you can now use SplitNB in SA Tools to extract both models and animations from NB files.

The next logical step was to try and recreate those NB files from actual models and animations. That was pretty complicated since I couldn’t just write out the whole model – I needed to break all its data into sections. Same with animations, which had to have rotations and positions stored in separate sections with correct pointers to them in the motion data section.

So I managed to rebuild NB files from models and animations extracted from them previously. ZERO worked right away, but with E101R the game froze while still playing the music. After comparing original and recreated sections I found the culprit – one of the motion sections didn’t match. The original motion’s rotations section contained two rotation keyframes that my code wasn’t picking up, and the resulting section was 32 bytes smaller. But when I looked at those rotations I found out why they weren’t being picked up – they weren’t referenced anywhere in the file. Unused/leftover animation data? I don’t know, but because it’s unused, the program doesn’t include it in the extracted animation, so the rebuilt section doesn’t have it either.

But even then, why would the game freeze if the data included in the file is correct and all pointers are valid? I open the disassembly and I see this shit:

So yes, despite being able to load a pretty elaborate container format, the game uses hardcoded offsets for models in NB files, which makes any NB file rebuilding useless without additional modification of the game’s code.

Can this be worked around? Sure, if you change the offsets in code to match those in your NB file it might work. Also it will certainly work if you rebuild the file in a way that keeps original offsets for models, though it limits the possible scope of modification quite a lot. It’s disappointing because I wanted to make SA Tools support splitting and building these files for easy modification, but this hardcoded stuff is too much effort to change such specific parts of the game. I’m still going to update SA Tools with a tool to rebuild these files for lighter edits, so at least we can have that. Oh, and if you just wanted the models or animations for use in other projects, you can already have them.

This concludes my investigation into SA1/DX NB files. If you’re interested in the specifics of the format, SplitNB source code has some documentation.