README.md



rapidriter-cat
This is a simple Rust program to animate a silly cat on the Rapid Riter at the Recurse Center. I hope it also serves as a useful template.
Aside from the meat and potatoes that actually animates the cat, it also includes a simulator for the Rapid Riter. This simulator allows viewing the frames in your terminal, or creating a gif.

Demo
Demo!! (This is already out of date)
But don't worry, there's also a gif!

The gif is generated from Gitlab CI, so it will always be up-to-date with the code.

What the Rapid Riter Expects
From the documentation:

implement a next_frame function with the signature: next_frame(frame: u16, ptr: *mut u8) -> u8

first input is the current (zero-indexed) frame
second input is a pointer to the 456-byte array
return value is zero if you have more frames to render, one if you're done rendering things
But you only get 100 frames, don't be greedy!


In this repo, this function lives in lib.rs.

Building
Just run make. The WAT (WebAssembly Text) file will be created at target/rapidriter-cat.wat, which you can then upload to the Rapid Riter.

Simulating
There's a simulator available by running cargo run. By default it will run your animation in the terminal. Alternatively, you can pass in a -i flag (i.e. cargo run -- -i) to run the simulator in interactive mode. This lets you step through frame by frame, which can be useful for ensuring everything is pixel-perfect.
Finally, you can specify an output (cargo run -- --out output.gif) to create a gif of your animation. This will run at 10 FPS, just like as it does on the Rapid Riter.

Compile-time image munging and build.rs
This script relies on two images, which can be found in the src/assets directory. At compile-time, the build.rs script takes in these files and turns them into a bit array which represents the image's pixels. This is then used in lib.rs at runtime to actually create the animation.
Notably, the two image file names (cat and meow) are hardcoded both in build.rs as well as lib.rs. It would be nice to clean up the former to be more generic but the latter is likely always going to need to be hardcoded (but that, imo, is fine).

Using this project as a template
This project handles a lot of boilerplate that you may want for your own Rapid Riter projects. As such, it may be useful as a template!
Notably, this project provides:

A simple build system
Gitlab CI/CD
Compile-time image parsing into a bit format (the exact format the Rapid Riter expects)
A simulator

To use this project as a template, you probably want to do the following things:

Change the package name in Cargo.toml

Update build.rs to reflect your asset names, or remove build.rs entirely if you have no assets
Update lib.rs to match your vision
Bon appetit!

Have fun and don't forget to meow! Meow meow meow meow