Modding and restoration discussion

[pez2k]

Although, how exactly does this work? I mean, what model structure should I use?
Should I include wheel model into the car model like it is in the GT2 Car Viewer?
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And also, why exactly is it limited to 255 vertices and how does that work? I mean, the original models include 3 lods in one file, even trough highest lod can use all 255 vertices available...
...
I never encoutered anything like 16 colors per face, can you go into a bit more detail about that? How can I setup my PSD file to work with theese limitations? How many colours can a texture have at all? Does this mean that every single polygon must have no more than 16 colors or am I getting something wrong?

The game generates the wheel model, it's not part of the game model itself. GT2CarViewer does a lot of work to mock things up rather than showing the data how it really is.

The model is limited to 255 vertices because the vertex count is stored in a single byte. Each LOD is an independent model in the same container, so you can use all 255 on the first LOD without 'running out' for the other LODs - see the Calibra DTM for an example of pushing the limit.

The textures in GT1 and GT2 are 16-colour bitmaps. The CDP file format includes the bitmap data, plus up to 16 16-colour palettes. The first palette is always used for the wheels, the last two are the brake lights by convention. Each face of the model includes the ID of which palette it should apply to the texture. This does indeed mean that each face can only use 16 colours, as it can only apply one of the palettes, and in reality those 16 colours are shared across whole areas of the car else you'd run out of palettes very quickly.

GT2CarViewer again mocks things up when it comes to textures, and creates a 256-colour texture with all of the palettes merged into one where it thinks they should be used. Using GT2TextureEditor to extract the data from a car texture would give a better idea of how it fits together - GT2CarViewer is purely dumping things in the nicest way to view, and exports in formats that would be impossible to re-import.

 

[SWAGMASTER69]

The game generates the wheel model, it's not part of the game model itself. GT2CarViewer does a lot of work to mock things up rather than showing the data how it really is.

The model is limited to 255 vertices because the vertex count is stored in a single byte. Each LOD is an independent model in the same container, so you can use all 255 on the first LOD without 'running out' for the other LODs - see the Calibra DTM for an example of pushing the limit.

The textures in GT1 and GT2 are 16-colour bitmaps. The CDP file format includes the bitmap data, plus up to 16 16-colour palettes. The first palette is always used for the wheels, the last two are the brake lights by convention. Each face of the model includes the ID of which palette it should apply to the texture. This does indeed mean that each face can only use 16 colours, as it can only apply one of the palettes, and in reality those 16 colours are shared across whole areas of the car else you'd run out of palettes very quickly.

GT2CarViewer again mocks things up when it comes to textures, and creates a 256-colour texture with all of the palettes merged into one where it thinks they should be used. Using GT2TextureEditor to extract the data from a car texture would give a better idea of how it fits together - GT2CarViewer is purely dumping things in the nicest way to view, and exports in formats that would be impossible to re-import.

Thank you, I have a much better understanding of the limitations now.
Working to fit in theese will be quite a challenge.

I'll do my best and try to remake a model with theese limitations:

255 Verticies, unlimited polygons(Well, they don't matter,right? They can easily overlap the amount of verticies I mean)

256X224 Texture sheet, 256 colors max, no more than 16 colors per "part" of the car...(Taillight for eample, or side of the car) and no more than 16 color pallettes. Can i use same palletes for multiple "parts" though? For example, use same palette for side mirrors and for hood texture parts?

And i can make only the highest lod (for testing purposes) and not include wheel model (but include wheel in the texture)

Seems ok?

 

[submaniac93]

Multiple different portion of the car can (and very much will) share the same CLUT (color look up table - aka 16-color palette). For example, GT often combines mirror texture with windows, as the colors used are pretty much similar. It's up to you to paint everything within the alotted total of 256 colors (in 16 16colors sets)

I will also add, mainly towards the 'unlimited faces' comment, that the combined LODs, the shadow mesh and the required pre-meshes data at the top of a CDO/CNO (object) file must not be more than 5000hex/20480 bytes long.
It's not something you can know until you have a model into the format itself, but that's a hard limit, as that's exactly how much space in RAM is alotted to any loaded car model.
The 20481st byte is the beginning of the second car loaded, so AI1.

 

[SWAGMASTER69]

Well, although I kinda understand how all this works, there's still a problem I can't solve: One part can only use one palette, for example, wheel uses palette #1, but how do i assign them? I work in Photoshop, and the trouble is the order of colours in palettes.

For example, my window texture will only use 16 colors, which is mandatory, but those 16 colors can be spread across everywhere instead of one palette when using photoshop. Is there a better way to control this, or a software that could ease this process...?

 

[submaniac93]

There's none to be honest. The best you could do is create all the textures that will use a single set of 16 colors in your texture map, then export the palette. Then work on a new palette where you'll do other parts that share colors. Stuff like that.
I could recommend using Paint Shop Pro 7 rather than a modern photoshop for a few reasons, as PSP7 is the standard for our toolchain for texturing. Because it easily works in 16colors mode, and our tooling exports palettes in its palette formatting.
I've joined an example from GT2. Our tooling (pez's i should say) exports and imports as pez said above, a bmp image that's basically used as the pixel data only, and a bunch of palettes, to be loaded in psp7 and edited there.

 

[SWAGMASTER69]

By making a lot of cuts on details and saving points everywhere I can I have been able to cut the model down to just 232 vertices. This is by no means final, but besides textures, I'm running into problems surrounding PS1'S interpritation of polygons.

I've heard it lacks Z-Buffer, and that's a major point that creates it's own problems and shortcuts.
For example, PD used this to make taillights on some of the cars in GT2, basically there are 2 polygons on the same place at once, one has a texture of the taillight, and the other one has a texture of the bumper (for example). And PS1 renders this model in such a way that you can see the taillights, even trough you really shouldn't be able to. This image should explain what I'm saying.



So the question is: I'm cutting corners everywhere I can, and that means getting rid of the 3D suspension in favor of a more simple, "semi-3D" variant. The variant on the right of the car uses more vertices than on the left, but if I'll use the left suspension, will it render trough the car's body in the game?





I want to have a better understanding of the rendering techique in GT2 to make sure that everything works fine from the first try.

I know I might be asking a lot of questions, but I think it's for a good purpouse. Making this F1 car work in the game is no easy task, and it might be even harder than a regular car, but that's the beauty of it, making something unusual possible! And this design forses solving problems that don't usually occur,but sometimes do.

 

[pez2k]

How the sort order of faces exactly works I'm not sure is fully understood, nor do I know how it will be set up in any potential model conversion tools. There is data per face that controls it, I don't know if reliable results have been produced with it.

 

[submaniac93]

The rendering order of faces that use the same vertices is through which is first in the hierarchy within the file. So basically, create first the face you want to be on top, then the face you want on the bottom, i guess?
The fact that this 'layering' of faces exists in that format, but it unsupported (as far as i know) by current modeling programs, makes it difficult indeed.

As for faces that aren't sharing the same vertices, Polyphony worked around the lack of Z buffer by having a render priority byte of sorts, that will kind of do the trick most of the time.

 

[SWAGMASTER69]

So after some learning and investigation I think i've made a F1 car model that should compile with the restrictions and have no problems when importing!



It's 248 verts, even less polygons, it's got 4-bit 16 color .BMP texture and 13 palettes of 16 colors for it.
Readme mentions that I don't know whether i should edit palettes in PSP to have total black as alpha or not, but if anything happens - it's the first color in every palette so it will be easy for you ti change it.

If that model works out, I'm willing to make a tutorial on how to make a model like this and more importantly, how to manage textures and palettes in Photoshop to make it work.

I'd be more than happy if you guys test this one out in the game and it works

I've used a lot of fun and ancient techniques that Polyphony uses in their models,and if all goes well, I'm willing to try and make it have normals on not every surface the easy way and include that into tutorial. (As I've heard, surfaces with no normals have no reflections, which is omportant for soft tops, etc.)

Edit: And just like original files, the first palette is wheels, the last one is Taillights On and previous to las is Taillights. And the F1 Espace sound should fit it nicely!

Here's a link for the model

https://disk.yandex.ru/d/R5ptmlWWGNX-iQ

 

[CaravanSS76]

The menus are more than just graphic images, I take it.

So after some learning and investigation I think i've made a F1 car model that should compile with the restrictions and have no problems when importing!



It's 248 verts, even less polygons, it's got 4-bit 16 color .BMP texture and 13 palettes of 16 colors for it.
Readme mentions that I don't know whether i should edit palettes in PSP to have total black as alpha or not, but if anything happens - it's the first color in every palette so it will be easy for you ti change it.

If that model works out, I'm willing to make a tutorial on how to make a model like this and more importantly, how to manage textures and palettes in Photoshop to make it work.

I'd be more than happy if you guys test this one out in the game and it works

I've used a lot of fun and ancient techniques that Polyphony uses in their models,and if all goes well, I'm willing to try and make it have normals on not every surface the easy way and include that into tutorial. (As I've heard, surfaces with no normals have no reflections, which is omportant for soft tops, etc.)

Edit: And just like original files, the first palette is wheels, the last one is Taillights On and previous to las is Taillights. And the F1 Espace sound should fit it nicely!

Here's a link for the model

https://disk.yandex.ru/d/R5ptmlWWGNX-iQ

The "hidden" CLK Race Car sound (same file with different toning) should fit it too

 

[SWAGMASTER69]

Never thought it would be so much fun to make models with such huge restrictions!
I'm currently working on a base Countach that could later be modified into anything. Just to sharpen up my skill on lowpoly, because it has a very simple shape, which allows for more smaller details like mirrors and logos to be added. Trying my best to keep it's stile close to the original GT models, and that's a lot of work

Can't wait for public release of the modding tools and start making cars for addons! And it would be so exciting to try theese on some real hardware! You guys are epic!

 

[CaravanSS76]

Nice content you're bringing there
btw, I would put Escudo or GT-ONE LM (preferably Escudo) physics with MR drivetrain in the F1 =D

 

[SuperFrizzio]

Good work! Can't wait to see them implemented in Gran Turismo 2!

 

[CaravanSS76]

Suggestion: Try to convert this:
https://3dwarehouse.sketchup.com/model/1ca17f99-8c70-4ead-970f-b92907f42ad0/Volkswagen-Gol-CL-1993
Also, can you remove the rear badging from the car? I didn't like it
It's a 5k poly car, but judging by the car's LOD I think it still would look nice with 255 polys

 

[SWAGMASTER69]

Suggestion: Try to convert this:
https://3dwarehouse.sketchup.com/model/1ca17f99-8c70-4ead-970f-b92907f42ad0/Volkswagen-Gol-CL-1993
Also, can you remove the rear badging from the car? I didn't like it
It's a 5k poly car, but judging by the car's LOD I think it still would look nice with 255 polys

I'm only doing this in my spare time, and I'm pretty busy with my own game. That makes me unlikely to do models on request, I'd rather make something that everyone would find exciting than just an ordinary car. Moreover, none of the models from the website you've mentioned are any good at all, but even if they were, in case with GT2's strict restrictions, It's much easier to just start from scratch.

But I've heard you, if I'll have enough time, I will look into the car, the shape is not that hard to replicate

Currently I think I want to finish that Countach and try to focus on a replica of an CLK race car that never made it into the final game in any shape or form, and is only seen in a couple of screenshots. That would be a real challenge!
And there's plenty of other cars I'd like to try and model too, Like for example the famous Mclaren F1 that was featured in the US art of the game, but never made it into the game.
I don't want to go crazy and ruin the older spirit of this beautiful game by adding something modern or unfitting, only era-specific or older cars

Talking about modding and tools, I'm also currently building a couple of old-fashioned PC's to handle various older programms and Operating Systems that PD might have used while making GT and GT2. It might open some new opportunities or just be a beautiful glimpse on how the things used to be. I'll share some footage and info when I'm finished.

 

[SuperFrizzio]

Nice. Also, @submaniac93 made a Mercedes Benz CLK-GTR long time ago along with a few Subaru Impreza race cars. A McLaren F1 would be cool to see, just to bring to reality an old rumor of it being in the game.

 

[SWAGMASTER69]

Nice. Also, @submaniac93 made a Mercedes Benz CLK-GTR long time ago along with a few Subaru Impreza race cars. A McLaren F1 would be cool to see, just to bring to reality an old rumor of it being in the game.

Hmmm...never seen one. Are you sure? I'd love to take a look!
I'm talking about this one, just to clear things up. This is what I would call a challenging recreation and a very exciting car to make

 

[submaniac93]

I did start on my take for it 2 years ago, but i never completed it (mostly laziness since it wasn't even possible to make it for the game really)

Clearly has placeholder textures lol

 

[CaravanSS76]

You could use the GT4's Silverado SST stock exhaust for the sound files, I think it will sound good for the CLK GTR

 

[SWAGMASTER69]

I did start on my take for it 2 years ago, but i never completed it (mostly laziness since it wasn't even possible to make it for the game really)

Clearly has placeholder textures lol

That's some good effort!
Well, I hope that we will start this modding jorney soon. I imagine it still won't be so simple, cause you have to set up all the parameters for the car like wheel positions etc., but the more we will dig into it, the faster and better the results will be.

I'm pretty sure I found a perfect and simple, straightforward workflow for both textures and Models with Normals on selected faces, but the models need some ingame testing to make sure that it works perfectly before sharing.

 

[SuperFrizzio]

Yeah, commongear said that he's cleaning up his code a bit before releasing the OBJ to CDO tool, so we are pretty close to start the journey.

 

[RandomCarGuy17]

I did start on my take for it 2 years ago, but i never completed it (mostly laziness since it wasn't even possible to make it for the game really)

Clearly has placeholder textures lol

That still looks pretty good, almost like it was meant to be in GT2. Though yeah, it could use some revising.
Once things are ready, maybe it'll be time for you to finish it.

You could use the GT4's Silverado SST stock exhaust for the sound files, I think it will sound good for the CLK GTR

Errr, I'm not sure if that's the best sound sample choice. I would rather just at least use the sound from the 1998 CLK LM (yes, I know it has a different engine).

Either that or just see if you can use a sound from one of the games that had a CLK GTR.

 

[CaravanSS76]

That still looks pretty good, almost like it was meant to be in GT2. Though yeah, it could use some revising.
Once things are ready, maybe it'll be time for you to finish it.


Errr, I'm not sure if that's the best sound sample choice. I would rather just at least use the sound from the 1998 CLK LM (yes, I know it has a different engine).

Either that or just see if you can use a sound from one of the games that had a CLK GTR.

GT-One has a good sound for it too
Do you know that the CLK DTM uses the same sound as some rally cars? Try to race with the CLK and Espace F1, with manual transmission shifting between 7-8k RPM

 

[RandomCarGuy17]

GT-One has a good sound for it too
Do you know that the CLK DTM uses the same sound as some rally cars? Try to race with the CLK and Espace F1, with manual transmission shifting between 7-8k RPM

Sure it does, but it wouldn't really work to use a Toyota racing engine on a Mercedes.
Also, yes I know; GT4 reused a lot of sounds between cars. Once again, I really think it should be a sound used from another Mercedes-Benz. So, the CLK Race Car would be my only choice you listed.

 

[CaravanSS76]

what about the racing exhaust of the CLK 320 Sports

 

[pez2k]

Not sure why lots of V8s are being suggested for a V12 sound - the Lister Storm is probably the best pick because it's also a big V12, and there aren't many others in GT2.

More critical than the sound is the physics, there's not really anything it can be based on too closely - the likes of the R390 maybe, but that and especially the GT-One were even less road-based than the Mercedes.

 

[CaravanSS76]

you can try the Elise GT1 or the Tommykaira ZZII too
For the V12, the Vector M12 LM also has a Lamborghini V12 engine

 

[submaniac93]

CLK DTM uses samples from the FTO for its sound. Take any FTO a'd give it a race exhaust in gt2 and you have a low revving CLK DTM.

Jaguae XJR15 has a nice enough V12, other than tvhat. Or i could stay true to how GT did it for gt4, and give it a Corvette C4 sound with race exhaust lol

 

[Mattiko88]

hello today playing gt1 i won a car i had never seen .. nissan silvia LM .. why didn't you add it to the gt2 mod? it's a show .. anyway can you tell me if there is something else interesting and different to discover on gt1? thankss

 

[MMRivit]

The Silvia LM's body is not present in any available GT2 demos, that's why it's still missing from GT2+ and other mods. It should be portable as soon as the CDO format is proven to be fully understood and research is done to document the equivalent format used by GT1.

As for other "interesting and different" things, not much in the retail versions apart from the Japan-exclusive content (NSX-R GT1 Turbo instead of LM GT2, different TVR Griffith racing modifications). The demos do have some juicy stuff people have been waiting to port over though.