jEnesisDS Question

Discussion in 'NDS - Emulation and Homebrew' started by Skyline969, Feb 2, 2009.

Feb 2, 2009

jEnesisDS Question by Skyline969 at 7:04 AM (2,538 Views / 0 Likes) 11 replies

  1. Skyline969
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    Member Skyline969 MENUdo Afficionado

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    Is there an option I can change so I don't have to press L or R to scroll around the screen? I'd prefer it if the entire view was just there so I don't have to worry about scrolling to look for enemies in certain games.
     
  2. Another World

    Former Staff Another World Emulate the Planet!

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    its a limitation of the way the emu is coded. you have to sacrifice something to get better speeds, horiziontal scailing was that thing.

    -another world
     
  3. Skyline969
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    Member Skyline969 MENUdo Afficionado

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    Hopefully in a future release of jEnesisDS, there will be a fast and efficient method of scaling that also quickly draws all of the layers.
     
  4. granville

    Member granville GBAtemp Goat

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    If you want full scaling, you'll have to live through about half the speed and no sound.

    As for this emulator's life, Lordus seems to have disappeared off the face of the internet. He hasn't posted in months.

    If you do want a Genesis emulator on DS with scaling, you can get either PicoDriveDS or the 0.4a version of JenesisDS. Both work pretty much the same. Here's the 0.4 version:

    http://library.dev-scene.com/index.php?dir...sisDS_v0.4a.zip

    the software version of the emu is the one you'll want to use to get scaling. It's slow and without sound.
     
  5. Skyline969
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    Member Skyline969 MENUdo Afficionado

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    Crap... sacrifice speed and sound for scaling? Forget that! [​IMG]
     
  6. DanTheManMS

    Member DanTheManMS aka Ricochet Otter

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    Right, in essence there are two possible ways for emulators to work on the DS. The first is called software rendering, and in this mode, the DS has to figure out exactly what the screen should look like each frame and then paint it to the screen pixel by pixel. This is how an emulator for the PC would work, and since the image is created in memory, you can modify it however you want before painting it to the screen, whether that be scaling or applying a filter or whatever. The problem is that it takes a lot of CPU time to first calculate what the screen should look like, and then even more to manually update every pixel on the screen 60 times per second. This is why frameskip helps - if it doesn't have to update the DS screen for every frame of Genesis emulation, it can spend more time on emulating the Genesis CPU itself.

    However, the DS (being a video game machine) has dedicated 2D hardware and special modes that let it plot sprites and backgrounds and tiles to the screen very very quickly. Thus, what jEnesisDS does is act as a translator between the Genesis's "draw stuff" commands and the DS's "draw stuff" commands without bothering to figure out what the entire screen is supposed to look like. Since the Genesis's video hardware and the DS's 2D hardware are not identical, translating between the two is a bit difficult to manage, and that's why you get graphical glitches on occasion, and why some of the more complicated effects cannot be emulated properly. Also, because you're directly mapping tiles and other graphics to the screen, you cannot scale horizontally. The reason you can scale vertically is because the 2D hardware keeps track of which row it's drawing to, and so you can simply skip a row here or there to squish the image vertically. The same cannot be done horizontally simply due to the way the hardware works.

    With hardware emulation, you can reduce the amount of CPU time spent drawing to the screen to less than 10%, which is why you don't see frameskip implemented, as it would have very little effect. jEnesisDS uses the extra time it gains by using hardware emulation to emulate the audio engine and maintain full speed during gameplay.
     
  7. mc_B3oWoLF

    Member mc_B3oWoLF GBAtemp Regular

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    And what about "heavy" roms?)))
    Could anyone (Lordus has been off-line for a long time, so i hope anyone else could help)) somehow add the "RAM expansion" support so that jEnesisDS became able to run such magnificent games as MK3U (Mortal Kombat [4] 3: Ultimate) and others?
     
  8. granville

    Member granville GBAtemp Goat

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    We can't add anything since only Lordus has the source code.
     
  9. mysticwaterfall

    Member mysticwaterfall Streamforce Supreme Commander

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    Ultimate Mortal Kombat for the DS is the same as UMK3, if not better.
     
  10. mc_B3oWoLF

    Member mc_B3oWoLF GBAtemp Regular

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    I can't fully agree with you..
    Yes, UMK DS is great, but still it isn't the original genesis MK3 Ultimate...
    by the way, not only MK3U doesn't work [​IMG]
    There are other large roms too and I guess many people would be happy to be able to start "phat" roms)))
     
  11. Taza

    Member Taza GBAtemp Regular

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    Yeah, only way I see scaling happening is cutting both sides by exactly half and drawing exactly one in every four pixels.
     
  12. DanTheManMS

    Member DanTheManMS aka Ricochet Otter

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    ...I have no idea what math you're trying to suggest there, but regardless, you cannot cut out columns of pixels when using a hardware renderer. It's just not possible with the way the emulator works.
     

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