SNES Doom Source Released! Now What?

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Maxwelthuthu
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Re: SNES Doom Source Released! Now What?

Post by Maxwelthuthu » Fri Dec 11, 2020 2:50 pm

The actual rendered area in both versions would look like this:

Image
128x72 on Genesis - 112x64 on SNES

Counting how many frames are repeated in one second, you can see that the SNES version runs at 30 fps and the Genesis version at 20 fps.
That's kind of a huge difference, they could used the same rendering size and level layout on SNES at 20 fps too. I don't know why they changed... maybe they disliked the framerate on Genesis.
The level still good tho, it just have some colision problems (Woody feels kinda fat).

Both versions also has a neat trick in one level, a background CPU rendered to look like 3 layers in one.

https://youtu.be/drr8t4sTqnw?t=1548

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Nikku4211
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Re: SNES Doom Source Released! Now What?

Post by Nikku4211 » Fri Dec 11, 2020 5:57 pm

Maxwelthuthu wrote:
Fri Dec 11, 2020 2:50 pm
Counting how many frames are repeated in one second, you can see that the SNES version runs at 30 fps and the Genesis version at 20 fps.
That's kind of a huge difference, they could used the same rendering size and level layout on SNES at 20 fps too. I don't know why they changed... maybe they disliked the framerate on Genesis.
SNES is 30 and Mega is 20 only to people living in NTSC regions(or PAL-M). This game was developed by people in the UK, so to them, the SNES version is 25 fps and the Mega Drive version is around 16.666 fps.
Maxwelthuthu wrote:
Fri Dec 11, 2020 2:50 pm
Both versions also has a neat trick in one level, a background CPU rendered to look like 3 layers in one.

https://youtu.be/drr8t4sTqnw?t=1548
Got to love how the SNES version is more colourful than the Mega Drive version.

Lol, they could have used mode 0, but nope. Instead, they flex their programming skills, not that I'm complaining.

If only someone combined this with the extra amount of layers mode 0 gives you...
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TmEE
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Re: SNES Doom Source Released! Now What?

Post by TmEE » Fri Dec 11, 2020 9:38 pm

I imagine the stage is probably 25FPS in 50Hz, the ~16% extra CPU time per frame and a whole lot more DMA time will help a lot in things like that. All the 3D games will run a lot faster in 50Hz compared to 60Hz just because of these things.

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Señor Ventura
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Re: SNES Doom Source Released! Now What?

Post by Señor Ventura » Sat Dec 12, 2020 7:02 am

TmEE wrote:
Fri Dec 11, 2020 9:38 pm
I imagine the stage is probably 25FPS in 50Hz, the ~16% extra CPU time per frame and a whole lot more DMA time will help a lot in things like that. All the 3D games will run a lot faster in 50Hz compared to 60Hz just because of these things.
The same for megadrive version, and the difference is still there.

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Señor Ventura
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Re: SNES Doom Source Released! Now What?

Post by Señor Ventura » Thu Feb 18, 2021 2:41 am

Having in mind the "mega color" doom version of genesis/megadrive, running from the cartridge with all the processing power of its FPGA... at 512 colors?.

What about if snes do the same in HD mode?, and, What about 256x224?.

Could be possible 512x120 at 4BPP and 15/20fps?.
And about normal resolution (256x120?), one port of doom running completely fron the cartridge, What color depth could it reach, no matter what the frame rate it can get?.


I can't do any calculations right now ^^

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Re: SNES Doom Source Released! Now What?

Post by tepples » Thu Feb 18, 2021 5:58 am

This effect relies on ability to write to video memory while rendering is turned on. The VDP has a write queue of four 16-bit words. It reserves some cycles each scanline for committing these words to VRAM, and if the queue is full, it can halt the CPU until a slot in the queue opens up. This is something that the Genesis does and even Super Nintendon't.

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TmEE
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Re: SNES Doom Source Released! Now What?

Post by TmEE » Thu Feb 18, 2021 1:39 pm

It actually turns rendering off for mostly offscreen parts every line so that it can do many more writes in short span than normal rendering process allows, it also avoids artifacts that would appear in middle of the screen in several predefined locations.

Image

The stuff seen in right edge are palette updates, rendering is disabled during the black portion and DMA started within it as soon as possible. I don't know how many entries are updated but I imagine 2 palettes worth at least. My own experiments allowed up to 3 palettes but it was difficult to avoid artifacts on left edge then. Also sprites are lost on those lines because rendering of them takes place in that part of the line.

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Re: SNES Doom Source Released! Now What?

Post by Oziphantom » Thu Feb 18, 2021 9:55 pm

load it up in MESEN and look at the even viewer should make it clear as day what it writes and how much.

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TmEE
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Re: SNES Doom Source Released! Now What?

Post by TmEE » Thu Feb 18, 2021 10:04 pm

There seems to be no Mesen for MD/genny, only NES, SNES, GB and GBC.

Oziphantom
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Re: SNES Doom Source Released! Now What?

Post by Oziphantom » Fri Feb 19, 2021 12:52 am

oh that is the MD version, my bad.

M2m
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Re: SNES Doom Source Released! Now What?

Post by M2m » Tue Apr 06, 2021 8:37 am

Maxwelthuthu wrote:
Fri Dec 11, 2020 1:13 am
Señor Ventura wrote:
Thu Dec 10, 2020 10:05 am
Oziphantom wrote:
Thu Dec 10, 2020 7:30 am
Given an A500 can't run Doom, even a A1200 can't really run Doom. A MD has no chance.

That being said the Toy Story 3D sections are pretty good. https://www.youtube.com/watch?v=LMWEknq-Now however single plane, no windows, simple geometry, no enemies etc etc
I post it quickly...

Image
The SNES version has a higher framerate, but there are less screen being rendered and the walls are way closer.
Both have scalled up screens, on Genesis is by software with some tilting to create dithering and on SNES by Mode 7.
Also, the screen is mirrored vertically to save processing.
The guy who worked on MD Toy Story has a pretty nice Youtube channel:

https://www.youtube.com/watch?v=OL3cuHoquUk

Might be helpful to reach out to him for further details and help ?

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