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Interactive VDP Documentation

Discussion in 'Technical Discussion' started by theocas, Aug 20, 2012.

  1. theocas


    Tech Member
    [​IMG] [​IMG] [​IMG]
    (Click on a screenshot to see it from real hardware)

    I've been working on looking more into the VDP and how it works it's magic for the past year or so, first writing this documentation, so I thought it might be a good idea to write some examples on how the various effects work, and thus this thing came about. It basically describes how many of the basic features of the VDP can be used to create effects, as well as some tricks used in games, followed by an example of them. I tried my best to explain it, but some explanations may be off. The ROM shows examples of patterns and palettes, nametables, sprites, vertical/horizontal scrolling, shadow and highlight, as well as pattern reloading. (If your emulator or flashcart supports SRAM, the ROM will save the last page you read, allowing you to continue from it later.)

    I plan to expand this with other stuff later - so if anyone knows anything that I've missed, please tell me and I'll hope I'll be able to implement it in the next version.

    That's really all I have to say - if you can't download the ROM, here's a video:

    Download version 1.0:

    Last, but not least, I'd like to thank the following people for helping in this in some form:
    * Jorge, Tiido, MarkeyJester - answering questions about the VDP and/or MegaDrive over the years
    * Oerg for testing and feedback, as well as being the original person I wrote the VScroll deform effect with
    * Sonic Boom for the horizontal scroll art

    I look forward to hearing your lot's feedback about this.
  2. LocalH


    roxoring your soxors Tech Member
    wouldn't you like to know
    Guitar Hero II Deluxe
    Nice, very nice. I assume the SRAM support will work on copiers like the Super Magic Drive? Might just have to copy this ROM over to my old WinME box and load it up on my Genesis sometime.

    Due to the way this ROM works, I almost want to see it in the font used by the BBC Micro in mode 7, which was used when viewing teletext on the system. I'm sure that Retro Britfags would agree with me :)
  3. theocas


    Tech Member
    SRAM should work with a copier - it's bog standard SRAM starting at $200000, and $A130F1 is used to activate it, so there isn't any reason for it to not work, although if no SRAM is present it just starts at page 1 =P
  4. Overlord


    Now playable in Smash Bros Ultimate Moderator
    Long-term happiness
    My first thought on seeing this was that it was very Teletext, actually. =P
  5. theocas


    Tech Member
    Haha, seems as if I managed to get that feeling right, then. I was actually thinking about Teletext when this came to me so =P

    I've also fixed a bug that caused Gens to hang (it can't emulate Z80 bus request right) and another bug that caused a few miscoloured dots in the palette view. Download link's the same.
  6. Meat Miracle

    Meat Miracle

    This is a very nice idea and I hope you'll manage to cover as many aspects of the hardware as possible.

    In fact I'd love to see stuff like this for all other Sega hardware too.