Cl-bodge: a cross-platform Common Lisp game and application framework

Cl-bodge: a cross-platform Common Lisp game and application framework(borodust.org)

93 points by bananaoomarang 5 years ago | 35 comments

There’s a small, somewhat quiet, but very welcoming and very vibrant community of Common Lisp games developers. #lispgames on Libera is where many of them hang out.

There are a few people who are trying their darndest to build and support libraries for graphics and other game-necessary things. It’s a tall order, since computers and operating systems have become so wildly complex and incompatible. (It’s no wonder people go straight for the browser to do little graphics things now.) Often it means finding a way to robustly interop with C++, graphics cards, etc.

Borodust, Baggers, dto, mfiano, and Shinmera are but a few Internet pseudonyms of people working hard along these lines. Shinmera in particular just released a demo of his team’s game Kandria [1]. It’s a cool and modern game with neat mechanics and effects. It’s powered in part by a ton of open source Common Lisp tools he’s developed.

[1] https://kandria.com/

nerdponx 5 years ago | |

I feel like this is a good time to shoutout to Baggers for the excellent "Little Bits of Lisp" Youtube series: https://www.youtube.com/watch?v=m0TsdytmGhc&list=PL2VAYZE_4w...

rgrmrts 5 years ago | |

On a somewhat related aside, the book Land of Lisp [1] is an interesting introduction to both Common Lisp and game programming. If anyone, like me, was interested in learning Common Lisp through a casual and fun mode, I highly recommend the book.

[1] http://landoflisp.com/

blacktriangle 5 years ago | | |

I generally recommend people avoid Land of Lisp as an introduction to CL book. It's simultainisouly too easy and too hard for most people approaching the language in that it goes way too briefly over core concepts then all of a sudden shifts gears into much more involved programming.

That being said, it's probably the best second book on CL ever. It showcases a variety of lisp techniques on some very real and fun example projects working itself all the way up to a web base game rendered via SVG which is quite fun.

crispyalmond 5 years ago | |

Even kandria itself is open-source (I believe) here[0].

[0] https://github.com/Shinmera/kandria

vladharbuz 5 years ago |

I think Lisp is wonderful, and I would love to develop games using Lisp. However, I was under the impression that, by all accounts, developing games in Lisp is completely unrealistic due to the garbage collector.

I'm not familiar with Common Lisp, but in Racket, “GC pauses [...] typically run from 50ms to 100ms” [0]. On a 16ms maximum frame budget, that doesn't really work. Am I missing something?

[0]: https://docs.racket-lang.org/portaudio/index.html#%28part._....

EDIT: I'm aware of GOAL at Naughty Dog — Andy Gavin who wrote it described the GC as being a problem in a HN comment. [1]

[1]: https://news.ycombinator.com/item?id=1998321

reikonomusha 5 years ago | |

You can write Lisp in a way that you manage your own allocations, including avoiding the heap. It defeats part of the point of Lisp, but sometimes you can use that coding style for a subset of your program that shouldn’t be leaning on the GC too much.

I don’t do game development, but in scientific computing, I rely on the GC a lot for workload preparation and other administrivia, then adopt a GC-famished Lisp style for the hardcore numerical computing part.

To be sure though, GC-less Lisp programming takes a great deal of effort and knowledge. It’s not exactly an a la carte option. But the fact it’s possible means latency-sensitive applications are possible. Fortunately, Lisp’s primary benefit isn’t the GC.

User23 5 years ago | | |

And with DISASSEMBLE[1] you can easily check to be 100% sure.

[1] http://clhs.lisp.se/Body/f_disass.htm

floxy 5 years ago | | |

Anyone know if there have been attempts at concurrent garbage collection in any of the major lisp implementations (whether CL or Scheme). Maybe Clojure?

bananaoomarang 5 years ago | |

Naughty Dog historically disagreed with this [0], plenty of games these days are developed in languages with GC but it is a performance trade off. For maximum performance any Lisp is probably not the way to go but I don't think it's unfeasable.

I want to say in general e.g. SBCL (a popular common lisp implementation) will perform a lot better than Racket. Racket is a great language but performance is not it's strong suit.

[0]: https://en.m.wikipedia.org/wiki/Game_Oriented_Assembly_Lisp

reikonomusha 5 years ago | | |

Currently, but hopefully no longer in the near future, SBCL’s garbage collector is extremely meh. It’s hard to tune, it stops the world, etc.

Otherwise SBCL is a wonderful implementation.

rgrmrts 5 years ago | |

There’s a lisp-like language without a GC called Carp [1]. I believe the goal was enabling real time applications and specifically games. I’ve only toyed with it a tiny bit, but it has an ownership memory model inspired by Rust. Pretty neat project!

[1] https://github.com/carp-lang/Carp

soegaard 5 years ago | |

The `portaudio` is a few years old, so I have a hunch that the comment refers to the old backend "Racket BC". The new backend "Racket CS" has a new garbage collection mode "incremental", which I understand is better for this usage scenario. I don't have any numbers though.

soegaard 5 years ago | | |

I got some more information from Flatt.

The new incremental mode means the 16ms deadline is within reach. In fact if the screen is not involved, then 1-2ms is reachable.

On macOS a screen-refresh can cause a 16ms pause.

phoe-krk 5 years ago | |

Kandria is written in Common Lisp and manages to deal with this.

https://kandria.com/

blacktriangle 5 years ago | |

I can't speak to the exact numbers, but in comparison to Scheme based lisps, CL has a much wider variety of optional hints you can give to the run time to drastically speed up performance thanks to its more pragmatic industrial heritage.

reikonomusha 5 years ago | | |

This is correct. You can declare the types of objects (DECLARE TYPE) which has repercussions on size and allocation, you can declare the type of optimizations you want to do (DECLARE OPTIMIZE) be them speed space or safety, and you can declare things to be stack allocated (DECLARE DYNAMIC-EXTENT), avoiding GC of a particular object altogether.

voldacar 5 years ago | |

It's worth mentioning that in general, racket is just a lot slower than SBCL. I would never write performance critical software in racket

moonchild 5 years ago | |

Andy derides the GC of a particular common lisp implementation (Allegro) and praises the GC of an implementation of a language with broadly similar semantics and data model (Ruby). The conclusion to take from that is that one CL implementation had a crappy GC, not that CL is not amenable to fast garbage collection.

borodust 5 years ago |

Author on the line. Thanks for the shoutout!

:cl-bodge itself is still an experimental tech that has barely any documentation - I won't recommend using it directly, unless you are happy tinkerer that ain't afraid of guts from hell.

:trivial-gamekit though is a stable framework that have much better documentation and strives to be as simple as possible. Nothing experimental about it. It's dangerous to go alone into jams with CL-based games, take gamekit with you. The fact that it is based on :cl-bodge at the moment is an implementation detail.

:alien-works is an attempt to reuse everything C/C++ gamedev world has and drive it from CL without too much blood bolting from eyes. It's not very experimental - just some conventional stuff piled together, but still is in early stages of development (although it has passed proof-of-concept phase).

We are, as in #lispgames community, indeed very welcome you to join us on irc.libera.chat:6697 in #lispgames channel. Some of us can also be found on Lisp Discord server[0] in #lisp-gamedev channel.

We also have community twitter account[1] which is not super active, but still alive. Just smells funny.

[0] https://discord.gg/hhk46CE

[1] https://twitter.com/lispgames

crispyalmond 5 years ago |

Also check out alien-works[0] by same author (borodust). This guy just works non-stop. I find it inspiring in a way.

[0] https://github.com/borodust/alien-works

bananaoomarang 5 years ago | |

Playing with their 'trivial-gamekit' based on cl-bodge now, very nice I think!

https://borodust.org/projects/trivial-gamekit/

alien-works also looks cool and under active development