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Sonic Xtreme Saturn 718 Hacking and Modding By DaGuAr And Andrew75

#31 User is offline XL2 

Posted 26 April 2018 - 02:14 PM

  • Posts: 43
  • Joined: 01-July 17
I did mess a little bit with it.

The "boss engine" is made using SGL and it's using the same base address for the text display as the default setting in SGL (it's also true for the POV demo).
It took me like 2 minutes to rip the HUD from VDP2 VRAM and put it in my own game.

It would also be super easy to rip the 3D model as we already have the layout of the polygon data (SGL PDATA), the only "hard" thing would be to find the starting adress in memory, but even that is not very hard, just time counsuming.

The textures are also just using 15 bits RGB data, so it's also super easy to rip those from VRAM.
typedef struct {
    POINT	*pntbl ;		/* 頂点の位置データテーブル */
    Uint32	 nbPoint ;		/* 頂点の数 */
    POLYGON	*pltbl ;		/* ポリゴン定義テーブル */
    Uint32	 nbPolygon ;		/* ポリゴンの数 */
    ATTR	*attbl ;		/* ポリゴンのアトリビュートテーブル */
} PDATA ;  // That's 3 pointers and 2 long, which means 5x4 bytes = 20 bytes. You can find the vertices, normals, attributes, etc. by looking at these pointers.



Each verticle is 12 bytes long, each polygon has 1 normal (12 bytes) and 4 vertices reference (8 bytes), while each attribute is 12 bytes long, as follow :
typedef struct {
    Uint8	 flag ;			/* 片面か両面かのフラグ */
    Uint8	 sort ;			/* ソートの基準位置とオプション設定 */
    Uint16	 texno ;		/* テクスチャ番号 */
    Uint16	 atrb ;			/* アトリビュートデータ(表示モード) */
    Uint16	 colno ;		/* カラーナンバー */
    Uint16	 gstb ;			/* グーローシェーディングテーブル */
    Uint16	 dir ;			/* テクスチャの反転とファンクションナンバー */
} ATTR ;




It's not using gouraud shading for the map (only the diamonds and Sonic AFAIK), but if you want gouraud shading you just need to change the attributes' gouraud shading value to point where you store your gouraud shading colors in VRAM.

It could also be easy to change the map, the only issue would be the pointers after the polygon data which wouldn't fit and would need to be changed (which would be a real pain) and the collision data (again, it's probably just using the SGL default collision code, which uses 1 point, a normal and a bounding sphere's radius, with a uniform grid layout).

In fact, there is even one SGL demo made by Chris Coffin in october 1996 which shows paletted gouraud shading using a hardware bug and a palette using different gradiants to create gouraud shading on paletted sprites (which should be impossible using VDP2 Color RAM). I don't know the exact cancellation date of Sonic X-Treme, but it's clear that Coffin reused lot of things he did within SGL's demos, such as the metal Sonic model and the Sonic model.
This post has been edited by XL2: 26 April 2018 - 02:42 PM

#32 User is offline Andrew75 

Posted 26 April 2018 - 02:50 PM

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  • Project:Project AXSX(Sonic Xtreme) + Misc Projects
I wanted to download some of the SGL demos that were already compiled into atlas packs which run on Saturn, they can be found on rockin B's website, but all the links are down. http://www.rockin-b....sgamepacks.html I also have SGL 3.02, but with so much going on, I never get a chance to screw around in trying to figure out how to compile them to run on saturn. Would like to see what they look like with my own 2 eyes at some point. Also if we can get ahold of SGL 3.2 someday. I hear tell that there was some amazing tech in that library which could more than double saturn's polygon pushing power.
This post has been edited by Andrew75: 26 April 2018 - 03:06 PM

#33 User is offline XL2 

Posted 26 April 2018 - 03:00 PM

  • Posts: 43
  • Joined: 01-July 17
You can download "Saturn orbit", which includes the SGL folder with all the demos.
Just open the "MAKE_COFF.bat" and it will create the iso, which you just need to load with an emulator.
You can find the model editor too, which includes Sonic, Metal Sonic, a sample map, etc.

As for SGL 3.2 - if it even exists - I really highly doubt it could double the polygon count, even by using the SCU DSP (which SGL doesn't) or the audio processors to do something else than audio you still couldn't get that far, unless they fully ditched what they did, but then it wouldn't simply be called SGL 3.2, it would be something like SGL 4 or whatever. Unless they meant processed quads but not displayed.

#34 User is offline Andrew75 

Posted 26 April 2018 - 03:05 PM

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I wanted to add that as you already know, we found Nack's model and Metal sonic's stage walls using hex editor, but did not see Metal sonics model in there. But that don't mean it's not in there. Because we only figured out about what half of the data was and crossed it off the list.

Edit:
According to my source, SGL 3.2 could produce over 1,000,000 polygons per second using a technique called AVR processing. I don't know how it worked or have any specifics.
Edit : yeah, ive toyed around with the model editors some years back. I think that someday, SGL 3.2 will surface somewhere. Would be nice to see what kinds of interesting tech demos it produced.
And thx for the info on Saturn, orbit ! gana try it later on tonight when I get back on the PC.
This post has been edited by Andrew75: 26 April 2018 - 03:30 PM

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