Awesome

libwfc

libwfc is a single-header C library for the Wave Function Collapse algorithm (WFC). It (currently) only covers the 2D overlapping model. WFC accepts a small reference image and outputs a larger image that resembles the input. See https://github.com/mxgmn/WaveFunctionCollapse for more details on the algorithm.

This project also offers a CLI and a rudimentary GUI tool for the WFC process.

Example run of WFC.

Quite a bit of effort has gone into making this library fast. See benchmark/ for some benchmark results.

Example run with a 256x256 output.

I also kept a devlog while working on this project - you can find it here if you're curious.

How to use the library

You only need wfc.h. Include it like this:

    #define WFC_IMPLEMENTATION
    #include "wfc.h"

Call wfc_generate:

    wfc_generate(
        // pattern width and height, 3 is a good starting value
        n,
        // options to control WFC, 0 if you don't want to enable any
        wfc_optFlipH | wfc_optRotate | wfc_optEdgeFixV,
        // byte size of a single pixel value
        4,
        // dimensions and bytes of the input image
        srcW, srcH, (unsigned char*)src,
        // dimensions and bytes of the output image
        dstW, dstH, (unsigned char*)dst);

There are other functions and ways of running WFC, check out the giant comment near the start of wfc.h for instructions.

If you want to test the correctness of the library on your system, run make test.

How to use CLI and GUI tools

Building

Run make to build both tools. Alternatively, make cli and make gui build individual tools.

To build and run the GUI, you'll need to have SDL2 installed on your system. You'll also need to have the sdl2-config program available.

Note for Windows

If you are on Windows, the process is slightly more complicated.

Installing SDL2 means downloading the files and dropping them in a directory (eg. C:\SDL2) and then adding that directory to your PATH system variable. You'll need both the DLLs and development files.

Since sdl2-config is not provided for Windows, I've written my own hacky version of it - check out misc/sdl2-config.

Whenever you're running make, add WIN=1 to the command. If you are using Microsoft's linker (and not, say, MinGW), also add VC=1. For example, make cli becomes make WIN=1 VC=1 cli.

Running

Run the CLI with:

bin/cli external/samples/Angular.png -n 3 -w 64 -h 64 -o bin/gen.png

And the GUI with:

bin/gui external/samples/Angular.png -n 3 -w 64 -h 64 -o bin/gen.png

Simply run bin/cli or bin/gui to see the list of possible arguments.

The library itself does not deal with file I/O nor with backtracking in case WFC runs into a contradiction. CLI and GUI both do.

GUI lets you watch WFC as it runs and you can pause/unpause it. You can also erase parts of the generated image and force WFC to generate them anew.

Example of erasing parts of image and generating again.

Contributing

For the time being, this is a single-person project, so please do not send any pull requests.

If you find bugs or have suggestions, create an issue to let me know.

Credits

Sample images were taken from https://github.com/mxgmn/WaveFunctionCollapse. See https://github.com/mxgmn/WaveFunctionCollapse#credits for more detailed attributions.

stb_image.h and stb_image_write.h come from https://github.com/nothings/stb.