Jaguar Lightgun

Shiuming Lai interviews Stone

Stone (Nick Bamji), based in the UK, is the probably the pre-eminent proponent of photon-play... We're happy he could spare some time to explain to MyAtari readers the story so far and road ahead for trigger-happiness.

Stone: The idea of using lightguns with the Jag was discussed on ugd-jag (the underground developers' e-mail list) for some time a while back. The topic seemed to spring up from nowhere. Lots of people on the list were very interested in the possibility of using a lightgun with the Jag so very fast Matthias Domin wrote some demo code according to the information in the development manual, and before long people had started converting all sorts of different console guns - I know people with [Sega] Master System, Atari XE and Atari 7800 guns, as well as some others. The main problem with their hardware implementation came up because of the Jag's matrix layout of the joypad, so by making a simple pin-to-pin adaptor for the gun's original connector made the trigger respond as if A, B, C and Option were all pressed together, which wasn't very helpful, or a particularly elegant solution. My fix for this was to rewire the inside of the gun (in my case a Sega Saturn gun) as well as changing the plug, so that on my gun the trigger responds as the Jag button B and the gun's Start button as button A on the Jag. As remarked by several of the people at the fest, Matthias' "quick-and-dirty" code actually worked surprisingly well first time, but although up and down were detected very well, there was an irritating "jitter" in the x-direction movement. This has now been fixed with the help of some cunning ideas from Tyrant, so the next step is to create a lightgun input module to run along with Starcat's development Library, which will enable any home-brew developer with Starcat's development CD to create lightgun-compatible games. One limitation in the hardware is that the gun input is only available on the first joypad port, and Team Taps do not support them either, so two-player gun games must be run with multiple Jaguars over a network, if this was desired.

Shiuming: Limitation of which hardware? The gun or the Jaguar? How did Atari Games' Area 51 coin-op, which was based on the Jaguar, manage two guns? Additional hardware?

Stone: The Jag hardware. There is no provision for more than one lightgun in the console itself, and there isn't an unused pin on Tom in such a position as to indicate that it was simply left off, so you can't simply add a wire to enable two-player gun support. The CoJag boards had to use extra hardware simply because the commercial Jag chipset cannot support two guns the way it is currently set up.

Even if it were possible to enable support by modding the Jaguar (which it's not) then I for one would still be very loath to write a game supporting two players on one console - there is no call or justification for forcing people to modify their consoles to be able to experience the full features of your game.

Matthias' code was very rapidly changed from a simple cursor-display program into the simple "balloons" game you saw at the fest, in which the player has to shoot down variously coloured balloons for absolutely no reward at all! Strictly proof-of-concept only, but hopefully we'll see some lightgun games in the future.

Now here's an explanation for why the last screen-shot was overexposed... Because of the way the lightgun works (tracking the path of the bright spot on the phosphor left by the electron beam as it moves around inside the telly) it works very very badly on dark areas, in fact it can't tell that it's moved position at all. This makes sense because there's no bright spot on black areas of the screen (as the electron beam is turned off as it passes them). Conversely it's very important for smooth tracking that the screen is as bright as possible all the time, so the gun can always "see" where it is and work out its position correctly. This means the screen looks to the gun pretty much like the last screen-shot and it's quite easy to detect where the balloons are. This isn't quite how it works but it suffices as an explanation of why the in-game shots are all so poor! By contrast the calibration screens come out well because only the calibration stripe needs to be white.

Shiuming: How do you plan to make lightgun games popular?

Stone: By writing a really good one! They'll sell themselves if there's at least one decent title to use with them; the problem is getting the time to do so around other projects. Reasonably far up the list is a lightgun module for the Starcat development library so anyone can play about with the ideas.

Shiuming: Having the games is well and fine, what about the hardware? Do you plan to pre-modify existing guns and sell them, like Tyrant does with his rotary controllers? Or is it at all possible to create a generic adapter module that can solve the simultaneous button problem, for a range of lightguns like the ones you mention, by way of on-board signal mapping selection?

Stone: If I was going to sell guns (this is all still very hypothetical remember) then I'd be selling pre-modded guns. It is possible to make an adapter to work with several different guns for different systems, but I probably wouldn't go down this route for several reasons; the guns may or may not be compatible with the way the Jag guns work (especially newer Saturn guns, this isn't so much of a problem with the old guns), the connectors are quite hard to get hold of and it's actually much easier to mod many guns individually than to design, build and test a seperate interface. It also removes most possible user error, which is a fairly high priority, nobody wants to have to remember to use the adapter all the time, or have it fall off and vanish under the sofa somewhere. It's much harder to lose a whole gun than your super-mini circuit board!

Shiuming: Why did you choose the Saturn gun? Is it technically better than the others? From a purist perspective, of course an XE or 7800 gun would be most appropriate!

Stone: No real reason, I just liked the design! They're much chunkier and more solidly-built than many of the other guns, they're not as old (and thus hard to get in good condition) and the biggest bonus is having an extra button on them other than the trigger. Other than that, I just like them! The only disadvantage is the colour, but if you import them from Japan they're moulded in lovely matt-black plastic (I've one waiting in my modding queue right now).

Shiuming: Are there any lightgun games on other platforms that you would particularly like to see implemented in some form on the Jaguar? Point Blank on the PlayStation is a fun game that could work well, I think. How about Barnyard Blaster 64, perhaps?

Stone: I've always been a huge fan of Virtua Cop, but I doubt it could be done in the same resolution/detail on the Jag. Something 2D yet fun like Point Blank would be nice to have on the Jag, certainly (no promises though!). As I've said, I've got lots of other stuff to concentrate on before getting into a full-blown lightgun game, so at the moment they'll stay as a nice tech demo.

Shiuming: Finally, I see you've had to fit a new plug on the cable of the lightgun, obviously to match the HD15 connectors used for the Jaguar controller ports. I've just had to fit the same type of plug to repair a VGA monitor cable and it was a pig to solder - 13 wires including three very awkward coaxial wires for the RGB components. How many pins are wired inside the Jaguar lightgun plug?

Stone: Six.

Shiuming: Great, give me a shout if you need help making a batch! Thank you for sharing that with us, we wish you all the best with this exciting project.

shiuming@myatari.net

MyAtari magazine - JagFest highlight 6, July 2003