sega's use of the SH-4

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Re: sega's use of the SH-4

Postby MetalliC » Fri Dec 14, 2018 3:23 pm

what's with Virtua Fighter 4 ? last time I've checked it was perfect for me. but afair there might be issues on some arenas for NVidia GPU users.
Hikaru - no progress.
anyway, I think will be much better move to Demul forum or Discord https://discord.gg/vpyRGPN for such talks.

as of Hikaru GPU mysteries...
and especially it's lighting capabilities, I doubt it was really capable of per-pixel lighting (i.e. phong). first known GPU capable of that was NVidia GeForce 3, thanks to it's fragment shaders. but GeForce 3 was released in 2001, while Hikaru much earlier - in 1999.
there is no known to me GPUs capable of per-pixel lighting of that years, and I HIGHLY doubt Sega was capable to develop advanced 3D GPU on its own.
currently I'm tend to think Hikaru uses GPUs from Real3D (similar to Model3) or 3Dfx Voodoo.

2Supermodel3 devs:
here is Hikaru GPU Command Processor src file (ignore the code, scroll down and read comments about commands - matrix, viewport, lightsources setup etc ), perhaps you'll see some similarities with Model3 Real3D ?
https://github.com/p1pkin/valkyrie/blob ... u-gpu-cp.c
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Re: sega's use of the SH-4

Postby Ian » Sat Dec 15, 2018 1:10 am

2Supermodel3 devs:
here is Hikaru GPU Command Processor src file (ignore the code, scroll down and read comments about commands - matrix, viewport, lightsources setup etc ), perhaps you'll see some similarities with Model3 Real3D ?
https://github.com/p1pkin/valkyrie/blob ... u-gpu-cp.c


Hm there are some similarities. But those similarities would be shared with any hardware of that generation really. Probably the last custom GPU by sega was the model2. The model3 they just used the real3d pro-1000 chip (with a few modifications). The dreamcast and by extension sega naomi they just used the powervr chip. They didn't develop their own GPU really. So my best guess is this is probably an off the shelf chip by some company. Would make little to no sense to a full GPU for what, 6 games? :o Maybe they simply added a hardware T&L chip or something.
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Re: sega's use of the SH-4

Postby MetalliC » Sun Dec 16, 2018 7:00 pm

I was asking about specific "control words / bit sets", which might remind Real3D Pro 100.
for example, PowerVR2-family have so called ISP/TSP/TCW - 3x 32bit words which controls everything rendering-related (Z-mode, polygon type, texture location and type, shading, blending etc). PVR2-based GPUs like DC/NAOMI "HOLLY" aka CLX2, or PCI/AGP card for PC "Neon250", or Naomi2 "ELAN" T&L coprocessor, have very different polygon/display list/vertices data input formats, because they have different "frontend". but all of them have in the input data (almost) same ISP/TSP/TCW control words, which is passed to underlying rendering "backend" core, and it is almost same in these GPUs.
so, I assumed Hikaru's "Command Processor" commands might contain "bit sets" similar to some known GPU control words.

in general, Hikaru's 3D display list is not similar to GPUs of that years. most, if not all, of them was more-less simple rasterizers, which had input data stream like the output of vertex shader stage of nowadays GPUs. not in the form of more high-level things like materials, models, transformation matrices, light sources, etc.

but yes, I'm too tend to think Hikaru had custom Geometry/Lighting coprocessor on the top of some off-shelf 2x GPUs.
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Re: sega's use of the SH-4

Postby PowerPC300 » Sun Dec 16, 2018 7:36 pm

i think so too, i thought they used powervr, as they were done with Lockheed. and i know sega couldn't do a project of this scale by themselves, (konami tried it and it was expensive). if it isn't powervr, what could it be?
Sega has made interesting hardware back in those days, the model 1, naomi, and don't forget the all custom hikaru!
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Re: sega's use of the SH-4

Postby Ian » Mon Dec 17, 2018 3:14 am

Get a picture of the board hardware. If the T&L chip is fabricated on a separate chip it's highly likely the output from this thing was just feeding a standard off the shelf GPU. I'd be super surprised if they developed a whole custom GPU for literally 6 games.

If you think it's outputting some sort of scene graph .. then there is only one GPU which would need this and that is the powerVR chip.There is another way to tell if it is a powerVR chip, and that is the way it handles transparency. PowerVR chips because they sort the geometry per pixel in each tile can render transparent elements in order .. and that means no funky transparency errors. In most games even on modern hardware if you start rendering transparent fire and smoke and glass together you'll quite often see alpha problems. Sometimes this can be solved by depth sorting polys. But if they intersect you then must sort .. at the pixel level which is not possible on other hardware (but it is on the powervr). The model3 had a totally different solution to this problem, and that was to composite alpha to a separate buffer, which meant only the top most transparent pixels would draw, which as far as I know is a totally unique solution.

If the colour output is dithered 16bit its a 3dfx chip. Otherwise its probably either ATI or Nvidia gpu hardware in there. Maybe matrox? Who knows :)
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Re: sega's use of the SH-4

Postby VirtuaHunter » Mon Dec 17, 2018 8:35 am

MetalliC wrote:what's with Virtua Fighter 4 ? last time I've checked it was perfect for me. but afair there might be issues on some arenas for NVidia GPU users.
Hikaru - no progress.
anyway, I think will be much better move to Demul forum or Discord https://discord.gg/vpyRGPN for such talks.



For VF4 (all versions) there is the corrupted graphics issue that happens on some stages.

I'll join the discord sooner or later thanks.
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