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PostPosted: Sat Oct 01, 2005 3:03 pm 
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I never meant to be mean or anything...

:(

I think the that there are 2 bottom lines when it comes down to emulation. 1. You write the emulator for fun or 2. You write the emulator for serious accuracy. I think that 1 wins hands down every time.

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PostPosted: Sat Oct 01, 2005 6:29 pm 
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I certainly agree that a claim of accuracy at the very least requires a pixel-accurate PPU rendering, not scanline-based. Maybe the criticism of inaccuracy is based on Nesticle and the common belief that it's the standard in accuracy.

But regarding goal 1 (fun), one needs a reasonable amount of accuracy for an emulator to be fun. When I first wrote my emulator it rendered the whole screen at once, so the status bar at the top scrolled with the screen. It was somewhat fun, but not near as much as when I improved it to scanline accuracy. There are so few games (that I know of) that require more than scanline accuracy that it's not worth it in terms of fun. Limiting accuracy to scanlines makes rendering simple to code and very fast (I can run 11 emulators tiled on screen at 60 fps on my 400 MHz Mac). Because of this, I think aiming for "mere" scanline accuracy isn't a reason for criticism.


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PostPosted: Sat Oct 01, 2005 7:45 pm 
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Can you make your scanline emulator emulate part-of-a-scanline? If so, it'd be easy to bring it up to pixel accuracy. Start by simply running the CPU ahead of the PPU and then having the PPU catch up to the CPU on every CPU$2xxx write. See which games screw up under that.


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PostPosted: Sun Oct 02, 2005 6:41 am 
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Can you make your scanline emulator emulate part-of-a-scanline?


Yes, I remembered this after I posted. Most of the time rendering covers multiple scanlines, which can be optimized using a scanline-granularity renderer (which actually renders n scanlines at a time, where n >= 1). When there's a partial scanline, then things need to be done pixel-by-pixel (for that scanline only). I guess the main barrier to this is the complexity and small benefit it brings. If there were more NES demos that relied on these things, it might be more encouraging for an emulator author to go all the way.


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