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VDP bug exploiting

Discussion in 'Technical Discussion' started by Sik, Aug 24, 2008.

  1. notaz

    notaz

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    Yeah, I think there should be at least one other game which used this feature. Charles' doc mentions Raiden Trad and Alien Soldier, but I haven't examined those.
     
  2. Snake

    Snake

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    It is NOT a bug. It IS a feature. It's present on pretty much every system with playfields, sprites, and priority settings. It isn't specifically documented because it's bloody obvious to a games coder.

    Except, of course, it actually IS mentioned in the SNES manual.
     
  3. Overlord

    Overlord

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    Presumably Nintendo thought its developers were a bit slow ;P
     
  4. roxahris

    roxahris

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    Well, at least then they wouldn't need to waste any more time than they needed to finding things with the hardware 8p
     
  5. muteKi

    muteKi

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    Well, since this is active again, I was thinking a good way of exploiting this feature would be to use it to do something similar to the title card lettering of Sonic 2 GG/SMS.
     
  6. Dr. Kylstein

    Dr. Kylstein

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    Is this what the Sonic 1 and Sonic 2 title screens use to hide the characters when they move into the ring? When I comment out the object loaded by sub_12F08 in Sonic 2, I can see them when they're below the ribbon.

    [​IMG]
     
  7. Overlord

    Overlord

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    Possibly, but I think that may just be standard layering...
     
  8. Dr. Kylstein

    Dr. Kylstein

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    The whole ring + ribbon is on scroll-A high. I have only prevented a sprite from loading.
    After looking at it in Genecyst, I think the part that is still on top in the screenshot is also using the exploit. There is a sprite there which has the top edges of the ribbon, but the part that is a full character tall has some random tiles from Tails(?). This suggests to me that it is never actually seen and only exists to make that part of A/H show up on top.

    I'm not confident in my understanding of the VDP, so I would really appreciate a response from somebody who is.
     
  9. TmEE

    TmEE

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    T-04YBSC-A !
    One of the sprite masking modes would be something that you could use in a case like this... I have not done any checking though...