Physics Games and Physics-Based Game Downloads

Matteo Guarnieri of Rag Doll Software kicks off our series of developer interviews here at Fun-Motion. Matteo is the sole developer behind Ragdoll Masters, a 2D rag doll fighting game. For more information about the game check out our Ragdoll Masters review.

FM: First of all, thanks for taking the time to do this interview! It’s great to have a chance to talk to you.

GM: My pleasure.

FM: Ragdoll Masters was released in May 2005, and the Radical Rebound domain was registered in July 2003. How long have you been making games, and what was your first publicly-released title?

GM: Wow, I’m impressed, I haven’t been looking back much, and time sure does fly. I started making games in late 2002 so it’s 3.5 years. Radical Rebound was my first released game, and I was so thrilled about it that I decided to call myself Radical Rebound Software and buy the radicalrebound.com domain.

Radical Rebound is a sort of shoot’em’up where instead of shooting at enemies you rebound their shots against them with a barrier in front of your shield. As of now it’s Mac only.

As I said this was my first game, and my first big programming effort (looking at it now it’s amazing how horribly coded it is!). Releasing something of yours in the big world for people to play with is something incredible: it makes you feel like an artist.

Originally it was free and I was happy with that, but one day I got a postcard from England with 10 euros from a fan. I can tell you that’s quite an amazing feeling, get somebody to pay for something you created. So I decided to go shareware in the following (much improved) versions.

FM: What inspired you to use rag dolls in a fighting game?

GM: It’s a long story really. I became interested in physics simulations in early 2004, particularly in balls (simulating collisions, gravity…). I enjoyed a lot the challenge of solving these problems and getting things to work.

One day I wondered if I could simulate a chain of balls. It appeared a very difficult problem. I dropped the problem, but some weeks later I had an idea on how to do it and after some time by trial and error I finally managed to get it working. I discovered later that the idea I had was very similar to the standard “vertlet integration” algorithm (sounds very complicated but the idea is really quite simple), one of the basics of ragdolls.

Ok, so I had a rope, now I wondered if I could do a man figure with it. Essentially it’s a matter of keeping the balls in a certain shape, so I though up a way to do it that now I call “elastic angle constraining”. Unfortunately I had problems with the math and gave up after 2 days of nightmarish calculations.

So after 3-4 months without coding anything, I played a very cool game called “ragdoll matrix”, which you can find on Google, and I thought “wouldn’t this be great if it was turned into a fighting game?”. So I got back to the problem I had left (the elastic angle constraining thingy), miraculously managed to get it working, and after a few months, the first version was done.

Of course I’m skipping all the technicalities and the painful moments where your code does not work and you have no clue why. Physics coding, even more than normal coding, can be extremely frustrating. You can get stuck on some small thing for days. In that case you just have to quit and hope that in a few day-weeks you’ll have the mind set to do it. It’s full of math, any small mistake can make it break. But getting some cool physics that works is just a great feeling, you feel a bit a “universe creator”. And you ask yourself how the hell did God manage to do such a cool physics engine.

After the first version, version 2 and 3 added more levels, opponents, variety, a co-op mode, much nicer gfx etc. Now the game is fairly complete, though they’re still could be space for new ideas or things to improve.

FM: Ragdoll Masters utilizes a simplified control scheme. Did you do any prototype or tests with different controls that would allow more articulated movement?

GM: I must admit that I borrowed the control scheme from ragdoll matrix. I just thought it was very clever and fun, and ideal for ragdoll masters.

It’s not easy to find alternative controls. The “ideal” thing would be having the player move every single joint choosing if contract it or extend it (as in real life), but this would require something like 30 keys and would be unplayable (hmm… that just gave me an idea for another possible game…)

FM: Have you done any tests with mouse-based controls?

GM: Well, yes, I made some tests where you can grab ragdolls with the mouse. It’s fun to throw them around, but it wouldn’t fit in ragdoll masters. Plus I tend to prefer keyboard-only games.

Speaking of which, I saw the trailer of rag doll kung fu, it looks fun even though i didn’t play it. The author thought up a rather interesting control scheme, and used the trick of anchoring the feet to the ground in order to prevent flying around too much.

As I told you, getting a nice control scheme for ragdolls is a pretty hard task. After all ragdolls were born to be “without control”.

FM: Do you play a lot of versus mode? Do you usually win? And can you personally play through all 20 levels of Ragdoll Masters (what’s your best score)?

GM: I used to play with a friend of mine, he was about as good as me. When I occasionally play with my other friends, I win ;).

No I only got to level 14. Just 1 or 2 guys (in the forum) managed to finish it as far as I know. I didn’t think it was possible.

FM: The AI in Ragdoll Masters does a pretty good job beating you down when you first start to play. How did you approach developing the AI for Ragdoll Masters?

GM: The level 1 AI is nothing special really. It more or less follows you. I put some effort making the higher levels AI, which are quite complex, but it turns out they make the game boring, since they defend too well.

FM: Sometimes I swear that my character will actually try to strike an enemy’s head. Is that my imagination, or is there really code in there that attempts to swing at an opponent’s nearby head?

GM: lol… no, its your imagination really :P

FM: Do you have a favorite physics-based game? What inspires you as a game developer?

GM: Hmmm… now that I think about it, no! I should try out more of them. I play many kind of games, usually small stuff made by single developers. Like Johan Peitz’s stuff is great and free. I also play online chess and bridge occasionally.

Some of my inspiration comes from other games, some from the physics I manage to simulate, some from ideas I just come up with. I always try to make my games simple, fun and original. Simple so I can program them, fun so I can sell them and original so I can feel proud of them.

FM: Finally, what’s next for Rag Doll Soft? I noticed you had some 3D rag doll tests posted in your forums. Can we expect Ragdoll Masters 3D?

GM: I made a physics based platform, for a contest, called N-Ball. I havent made much advertising to it but it’s there, you can find it on my forums [editor: right here]. I plan to making more levels and polishing it up, and release it as shareware too. It’s a game you might either love or find boring, it’s not as “cool” as Ragdoll Masters, and it takes a while to master.

Ragdoll Masters 3D? Possible. I’ve done the physics. Works great. I was amazed I managed to do it, without too much suffering, despite 3d math makes 2d math look like a joke. Looks like I’m gettin’ good at it :-)

Still I’m waiting for some idea. I’d like to put something new in it. Plus I have to work on the eye candy. Probably it’s going to be setup in a disco, with flashy lights, spinning colored lights and other cool stuff that opengl makes possible. And cool, matrixy camera work. Maybe it’s going to be called “Disco Fighters” :-) But nothing’s really sure at the moment.

FM: Is there anything else you’d like to say about Ragdoll Masters or Rag Doll Software?

GM: I think I said enough. Oh, no, wait, I wanted to thank you for the interview and mostly I wanted to thank again all the people that bought some of our games, and it’s quite a lot of people really. Thanks so much!