NES Sonic

[evildragon]

ahh, so it's 10.. i had no way to benchmark it... (i think the game clock is off, too)

the NES can really push itself.. Though, it you want to exceed the limits, you have to program around the limitation, and make programming that "emulates" more sprites, by not even using sprites in some parts...

[Genesis Knight]

Very nice - but for the framerate, it looks better than 99% of the official NES library.

[Melf]

That's pretty awesome, and it looks great for a NES game. I'd love to see the full version someday.

[Vyse of Arcadia]

In. Cred. I. Ble.

Absolutely amazing work, evildragon. Encore!

[evildragon]

glad you guys like it...

while over the weekend, i'll see if i can get some Chemical Plant vid's, and another level..

The other level, I'll let you guys decide... Be it graphically advanced, or just a speedy level.. I can only get about 25 second clips though... I really am trying to save space on my web server, cause im hitting bandwidth soon..

[evildragon]

here's another shot... More won't come until after the weekend.. I'm going to my mothers house, and I'm not taking any of my stuff with me..

http://blackevilweredragon.spymac.co...NESLoading.jpg

[Joe Redifer]

Do a bonus level! Better yet do a bonus level from Sonic 3D Blast! Do Halo 2!

[evildragon]

oh, before I go, I got some sound effects clips...

http://blackevilweredragon.spymac.co...EndSpinner.mp3
http://blackevilweredragon.spymac.com/Die.mp3
http://blackevilweredragon.spymac.com/Spring.mp3
http://blackevilweredragon.spymac.com/Ring.mp3

[evildragon]

Do a bonus level! Better yet do a bonus level from Sonic 3D Blast! Do Halo 2!

i'm already working on porting the Sonic 2 Special Stage.. That one, while the same pixels in width, is NOT easy to pull off on the NES, but I may have found a routine that actually works..

EDIT: Here, just for you, this is what I got working so far: http://blackevilweredragon.spymac.co...NESSpecial.jpg

[evildragon]

Since this is getting some interest, I'm taking some more screenshots, and might have a video of Chemical Plant, during a speed run, some time today..

http://blackevilweredragon.spymac.com/Aquatic.jpg
http://blackevilweredragon.spymac.com/CasinoNight.jpg
http://blackevilweredragon.spymac.com/Metrop.jpg
http://blackevilweredragon.spymac.com/Mystic.jpg
http://blackevilweredragon.spymac.com/OilOcean.jpg

As you might have notice, i'm having a palette problem.. Sonic's "blue" color changes slightly, and white sometimes turns blueish, and the Score/Time/Rings yellow counter sometimes turns a different shade of yellow, to match the game palette..

I'm not really hitting over 8 colors really.. I'm having a hard time programming palette separation (as I am doing some tricks to get some sprites over 4 colors)...

EDIT: Here's the video...

http://blackevilweredragon.spymac.com/SpeedRun.mov

(This one is MPEG-4)

[Alianger]

omg! and it's really fast too.. well done!

[evildragon]

Thanks!

Here's two more sound clip, and I'm done for a couple days...

WARNING! TURN DOWN SPEAKERS FIRST! I forgot to fix the volume on the soundcard when recording this, and it's quite loud..

http://blackevilweredragon.spymac.co...NESEmerald.mp3

It's buggy, but im sure you all know that tune..

http://blackevilweredragon.spymac.com/SonicNES.mp3

[tokumaru]

Hi evildragon,

I've never heard of you before, but I've been a NES programmer for a good time now, and your project really caught my attention. In fact, I'm coding a Sonic game for the NES myself.

I'm coding my game from the ground, trying to mimic most features of the Sonic games, in a way that is easier for the NES to work with. I know something about the engine used in the Genesis/Mega Drive games, and I'm very curious as to how you managed to port certain features.

So, if you don't mind, I have some questions:

1. The original 16-bit game has it's levels compressed in ROM, and these are decompressed to the 64KB of RAM the system has. How are you handling these levels on the NES, that only has 2KB of RAM? Are you using a cart with extra RAM? Which one? If you changed the format of the levels, what changes have you made?

2. How are you handling the water in Chemical plant? Does the mapper you use have IRQ's, that you set to fire at the level of the water? How do you make everything past that point purple?

3. What mapper are you using? I ask so that I can have an idea of the features you have avaliable.

4. What is the region of the NES you are using? Is it a NTSC NES, PAL NES, japanese Famicom, or evena famiclone? I'm curious, because the colors in your videos are pretty unique.

5. How did you manage to have som many sprites on screen? Since the NES only allows for 8 8-pixel wide sprites per scanline, the only way to have more than that is to alternate which ones you display each frame (through a process called sprite cycling), which results in them flickering. However, I can see no flickering in your videos, and I often see more than the allowed ammount of sprites (specially at the top, where the HUD is, as other sprites go up there). Did you achive that by updating the OAM memory mid-scanline, or something like that?

6. What code is it that you ported to the NES? Do you have a copy of the source code of the original game? Did you disassemble the game yourself? Can you point me to the code your port is based from?

7. When you ported it to the NES, did you also include some sort of frame-skipping system? I mean, the videos run at normal speed, but with some frames missing. A direct port to a lower end system should result in the game playing slower, but still processing all frames. Your engine seems to be emulating some of the things the NES can't handle, so maybe that's why you have a feature so common in emulators (frame-skipping).

I think this is all. This game seems very special, as it works around so many limitations of the NES hardware. I'd like to learn more about it.

If you have any questions about my project, I'd be glad to answer them.

Thanks for your attention.

[Bregalad]

Hey, your project look somewhat cool !
How did you convert the graphics from the Genensis to the NES ? The NES have much less colours, so I guess you had to manually convert all tiles of the game in a tile editor to look authentic on the NES. This should have been some tedious work, but the result looks pretty good, tough.

Also, the background looks NESish, but the sprites really looks authentic, I ask me how you made them. I suppose you used multi-layered sprites to get so many colors at once (only 3 are available per sprite normally), so that'd be a lot of sprites on the screen. Be cautionnous, because your sprites may not disappear on a emulator, but will on a real Nintendo, because you can only have 8 of them per line. So that may (and probably will) cause problems if your projects runs on a real Nintendo console (or an emulator parametred to behave with sprite-limitation enabled).

[evildragon]

I'll try to answer the questions as best as possible.

There is a memory upgrade done to this machine.. I am using a DVD-ROM drive I build for the NES (that uses the bottom expansion port), which uses a BIOS "cartridge".. The drive has 2MB of RAM, 768K of it exclusive only to the drive, the rest to the NES, and the drive.. The drive runs on an NEC V30..

For sprite limitations, I made a routine that emulates directly drawing pixel by pixel (essentially emulating a frame buffer).. This also got me around the sprite 4-color limitation..

The mapper I am using is the NEC V30 CPU on the drive, it is emulating the function of a frame buffer (by the BIOS on the drive itself...) it's address lines were essentially divided between the drive itself, and the NES... (it also routes the memory calls)

the frame buffer technique is doing frameskipping, yes.. I was wondering when someone would notice it's skipping isn't smooth, and it's really bogging (like my car, lol)..

The region is NTSC-America (if there's a difference between the Japanese NTSC system)..

The watter effect was done via the same way it was done on the Genesis, as that was a direct port from the Genesis code.. It's a mid-screen palette switch... The NES isn't known for doing this well, or at all.. The NEC V30 on the drive aids this for the NES, by directly accessing the NES CRAM and modifying the values itself (also by monitoring where on the level you are..) You can notice an effect of the V30 playing "catch up" in 2 frames.. Right when sonic goes down low enough, notice TWO frames are exactly the same, except on one frame, the watter is too low, not even in place, where the other frame the water "caught up"...

Come to think of it, the bogging might be the frame buffer emulation, and the DVD drive attachment doing nothing but "peeking" at memory (which does take a cycle from the NES's 6502 clone)..