A Raycaster in Bash

(github.com)

249 points | by izabera 15 days ago

18 comments

  • purplesyringa 14 days ago
    I love this. I've been wondering how the picture is drawn with less than one `echo` per pixel, and it's very clever: the game is "not really" 3D, so you can run raytracing just once per column, and then you only need to draw a couple of lines (for sky, grass, and the actual object) -- this is done by outputting the "draw this pixel and move down by one" string to the terminal as many times as necessary using string repetition.

    I've been considering working on a voxel render engine (not for Bash, but for another computationally limited environment). This is a treasure, I'm certain I'll find something useful here.

  • tdeck 15 days ago
    In case you wondered if there is a raycaster written in MS Batch:

    https://github.com/nTh0rn/batch-raycaster

  • Arch-TK 15 days ago
    It's unfortunate that stty requires forking. Maybe the next project will be to use bash and rowhammer to call the necessary ioctls to do it without forking.
  • alsetmusic 15 days ago
    I had no idea this was possible with Bash. I’ve considered myself proficient with Bash at a pretty advanced level at times and this just blows me away. I don’t have the math chops to understand how it’s implemented, but it’s a pleasure to see.
  • einpoklum 15 days ago
    And to think, that my own bash scripts spend 300 lines just parsing various command-line options, while instead I could be showing this game... :-P
  • 8n4vidtmkvmk 14 days ago
    I never ceases to baffle me how we're still stuck with these mind bogglingly slow shells. Pure madness. I can maybe understand that some apps require all the vt100 weirdness or whatever, but probably 90% of apps just write to stdout and err. Surely we can blit some text to the screen a bit quicker and put the other 10% into some compat mode.
    • PhilipRoman 14 days ago
      Shells are slow (particularly bash), sure, but I'm not sure how the rest of your comment follows from that. The shell is not involved in interpreting terminal escape sequences in any way, and modern terminals are quite fast - I can render animations in a 350-column terminal and they are as smooth as can be, given the constraints. Besides, the whole premise of this post is that bash is the wrong language for raycasting, kind of like writing bubblesort in CSS.

      >put the other 10% into some compat mode

      There is nothing preventing that, just test if the string contains sane characters only and use a fast path for that. The problem is that there is no actual fast path for software text rendering, you still need to process ligatures, etc.

  • markeroon 15 days ago
    Only 300 lines of code, impressive! I love this.
  • 1vuio0pswjnm7 14 days ago
    "bash is slow."

    That's in part why I do not use it for scripting. I do not use it for interactive use either.

    Some popular Linux distributions also avoid bash as a scripting shell.

  • Teongot 15 days ago
    I'd love to see this combined with the author's fork()-less implementation of ps to make a (almost) fork()-free implementation of psDoom.

    Seriously though, this is really cool

  • mmh0000 14 days ago
    Of course, we need to give an honorable mention to the `awk` raycaster from 9 years ago.

    https://github.com/TheMozg/awk-raycaster/tree/master

  • shric 15 days ago
    Beautiful. Correct me if I'm wrong, but this looks like a bash version of https://lodev.org/cgtutor/raycasting.html

    Edit: ah, just noticed this is in the readme :(

  • anfractuosity 14 days ago
    Very cool! I'm curious when it says "did you know that accessing a random element in an array takes linear time", why that's the case, with bash?
    • izabera 14 days ago
      normal arrays in bash are implemented as linked lists. bash stores a pointer to the last accessed element, which turns the most common case of iteration into O(1), but the performance is terrible if you need to jump around

      see some basic benchmarks here https://gist.github.com/izabera/16a46ed79c2248349a1fb8384468...

      there are also associative arrays which are bucketed hash tables, which are fine for string keys but imho they are hardly ever worth it as a replacement for indexed arrays

      • anfractuosity 14 days ago
        Thanks a lot, that's very interesting re. it using linked lists, and nice benchmark!
  • armSixtyFour 14 days ago
    Sadly I can't get this working. It just throws up the view into a file called buffered for whatever reason and exits immediately :(
    • izabera 14 days ago
      try `bash game.bash 2>errors` and see the content of that file when the game exits
  • mlconnor 14 days ago
    Wow, that’s an insane challenge. I can’t believe that’s even possible.
  • CaesarA 15 days ago
    I wonder if texture mapping this would look good.
    • Arch-TK 15 days ago
      She has been brainstorming how to handle texture mapping within the performance constraints of doing it in bash for a week now (long before she actually got this working) and so far we've come up with some hypothetical ideas but she has not tried any of them yet. Maybe tomorrow...
  • corytheboyd 15 days ago
    Imagine a TUI where you need to navigate a literal maze of options
    • Arch-TK 15 days ago
      Many CLI programs which take option have already managed to do this (in the text-based adventure game style).
    • jaynetics 14 days ago
      Like this one in Jurassic Park? https://youtu.be/URVS4H7vrdU Funnily enough, the slow rendering is kind of a plot device here.
      • Arch-TK 14 days ago
        The program from that scene was not some crazy invention for the purpose of having an interesting computer scene. It is a real piece of software for silicon graphics workstations called fsn (File System Navigator).

        There's a x windows remake of it called fsv: https://fsv.sourceforge.net/

        And then there's this even cooler UI which takes this whole idea much further called eagle mode: https://eaglemode.sourceforge.net/

    • krapp 15 days ago
      That's the kind of "futuristic interface" you'd see in a cyberpunk movie, and it would be incredibly annoying in real life.
  • ormaaj 14 days ago
    <3
  • jsheroes 15 days ago
    [flagged]
    • dang 14 days ago
      Please stop making accounts to break HN's rules with. It will eventually get your main account banned as well.