A Guide to the Graphics of the Sega Mega Drive / Genesis

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16 thoughts on “Comments”

  1. Honestly, I was already impressed by the work you are showing about the book, and I enjoyed reading through MD Shock, but this is the first time I’ve taken the time and I’ve really understood how the MD graphics worked. I suppose most of this info already existed on the internet, but this is an awesome newcomer BUT detailed guide. IMO that’s hard to make, as you cannot be 100% technical but you cannot be 100% theorical, and I really think you have nailed it. There are so many concepts I’ve read about on emulation but didn’t fully understand until now…

    I’ll forever be grateful for letting me understand my favourite console from youth. Keep doing what you are doing, because it’s hard to find this kind of content. Really thanks and good luck finishing the book!! Really looking forward to reading it!!

    1. It’s good to hear that some sense can be made of all of this! I think a lot of what it takes to understand the hardware is to just see as many examples as possible. I hope to add more examples as time goes, but I’m thankful to all the people online who are already sharing these examples because it takes a lot of effort to spot the more subtle ones.

      And I’m glad to hear you’re excited about the book. It’s really a dream come true to be able to write it.

  2. Hi!
    Can the shadow and the highlight be applied to specific parts of the screen at the same time? Or while I use one, can’t I use the other one?

    1. Lucas,

      Yes, both shadow and highlight can be applied at the same time to different parts of the screen. There is only one mode for shadow/highlight, and when it is enabled, both can be used. If we’re using sprites to do it, then any sprite pixel that is set to color 15 of palette 3 will shadow the planes under it, and any sprite pixel that is set to color 14 of palette 3 will highlight the planes under it. These can be used simultaneously.

      Off the top of my head, I don’t know of any good examples of games that used both at the same time, though.

      1. Thanks for the answer, Jharrison! Your website is incredible and very informative, I hope you continue with the posts.

        It is interesting how powerful this technique is, but unfortunately, few games have taken advantage of it.

        I’ll try to make an effort to buy the book, but as our currency started to devalue (Real – Brazilian), everything that is bought in dollar is very expensive for us. 🙁

  3. Hello guys, great article, I liked it a lot!

    I’ve had a question about S/H since Lucas commented. In Ranger X, are planes A and B low priority, while Shadow is high priority? Or is Plane B the only one with low priority?
    I ask this because I learned how to use S/H mode in some games that have similar engines to Sonic games, and it’s possible to activate S/H by changing some bytes via emulator. But look what happened, it looks like the plane A tiles break the shadow, even if the tiles are empty.
    https://imgur.com/gallery/ovVbF46

    Can’t plan A have a higher priority than the shadow activated between the planes without these breaks occurring close to the tiles, even if they are empty tiles?

    Thanks for listening!

    1. Hi Hamilton,

      It sounds like you’re talking about plane-based shadowing, so let’s ignore sprite-based shadowing/highlighting for now.

      For plane-based shadowing to appear on a particular tile, two things must be true: 1) S/H mode must obviously be enabled, and 2) BOTH Plane A and Plane B must be low priority at that tile location. Once those conditions are met, then the tile will become shadowed. There is no Shadow plane or anything like that (so it’s never the case that ‘Shadow is high priority’).

      In the Ranger-X cave stage, both Plane A and Plane B are low priority throughout the stage (so the entire stage is shadowed). When the player shoots the ceiling to let in the light, then one plane becomes high priority, which cancels the shadow effect at that location.

      In the case where you enable S/H mode in an emulator, you’ll only see shadow where both planes are low priority. If one plane (A or B) is high priority, even if it is transparent, then shadow will not be applied. For your Dynamite Headdy example, the foreground tiles in question have high priority, so they are not shadowed (even when they are transparent). It might be possible to reduce the high-priority transparent borders around the foreground objects a bit more, but I don’t know specifically.

      There’s no way to have foreground tiles at high priority and still use shadow at that tile position. This is one of the disadvantages of S/H mode– you can’t have the player pass behind a shadowed foreground object, for example.

      Hope that helps!

  4. What’s crazy is that the SNES presumably could do all of this too, thinking about that layer priority and line scrolling trick used in Thunder Force IV to create the illusion of far more layers in particular, and with up to two additional fully overlapping background layers depending on the background Mode used. It kinds makes me wonder why such techniques were rarely used on that system.

    1. Hi Kirk,

      Apologies for the delay in getting your post up – I had turned on manual comment approval to fight spam.

      I’m not that knowledgeable about the SNES by any means, but yes, as I understand it, the SNES could basically do all of what the Genesis could do (although through somewhat different means, such as HDMA).

      As to why these techniques weren’t used as much, I’d guess there are several factors. The first is that SNES developers were naturally attracted to the SNES’s Mode 7 capabilities like scaling and rotation, so they tended to build effects around those. The second is that most games (in my view, at least) on BOTH the Genesis and the SNES didn’t really implement many effects at all. The one effect you see a lot on the Genesis is line scrolling for the background parallax, and that’s probably because it was very easy to implement and very well documented in the Genesis software manual.

      1. OK, thanks.

        Yeah, I see examples of line scrolling being used on Genesis a lot and to great effect, and it’s just kinda sad it wasn’t used anywhere near as much on the SNES too. Donkey Kong Country 2 is one game that really takes advantage of many of these effects you’ve mentioned, I think, particularly on the underwater level in the ship (it has line/row scrolling on the really very convincing 3D-looking floors in the background plus on the top of the water and everything under the water for example), but it’s definitely the exception rather than the rule: https://youtu.be/RVzjFr6gprg?t=813

        It’s crazy to discover how much of this stuff was done on the Genesis and how so many games were actually using a lot of cool tricks like this, particularly when you see it at work in games like Thunder Force IV, Dynamite Headdy, Gunstar Heroes and Shinobi III and realise just how effective and simply nice looking it is.

        And modern homebrew devs/hackers seem to be getting even more out of the Genesis every day and exploiting these tricks and more even further for some stunning results. It’s great to see.

        I just wish some more modern homebrew devs/hackers on SNES would do similarly.

        By the way, this article is utterly brilliant for me in terms of learning about how all of this stuff is done on Genesis and just in general. I wish there was an article like this for SNES that was similarly well put together and clear to follow and understand with lots of really nice examples like the ones above to see it all in action.

        Great stuff.

  5. Does the SNES background layer 1/2/3/4 priority work similar to the Genesis Plane A/B priority, or can only the Genesis movie Planes viusally in front of and behind each other depending on how the priority is set?

    1. As I understand it, SNES background tiles also have layer priority (high or low), so the overlapping effect seen in Thunder Force IV should be doable on the SNES without problems.

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