Spatial LED (Sled)

What Sled does:

• It exposes an API that lets you:
  • Compute colors depending on each LED's position, distance, direction, line segment, etc;
  • Output colors via a simple, contiguous iterator for your own usage;
  • Filter LEDs by spatial properties to predefine important sets and regions for faster computation;
• Additionally, some tools are provided to help you build functional apps faster (you may opt-out via compiler features):
  • Driver - Pack draw/compute logic into a Driver to simplify the process of swapping between effects, or changing effect settings at runtime.
  • Scheduler - Lightweight tool to schedule redraws at a fixed rate, powered by spin_sleep.

What Sled does not do:

• It does not interface directly with your GPIO pins to control your LED hardware. Each project will be different, so it's up to you to bring your own glue. Check out the Raspberry Pi example to get an idea what that might look like.
• It does not allow you to represent your LEDs in 3D space. Could be a fun idea in the future, but it's just not planned for the time being.

This project is still somewhat early in development so please report any bugs you discover! Pull requests are more than welcome!

See the spatial_led_examples repository for examples of Sled in action!

The Basics

In absence of an official guide, this will serve as a basic introduction. From here, you can consult the docs to learn what else Sled can do.

Setup

To create a Sled struct, you need to create a configuration file and provide its path to the constructor:

use spatial_led::<Sled, SledError>;
fn main() -> Result<(), SledError> {
    let mut sled = Sled::new("/path/to/config.yap")?;
    Ok(())
}

A configuration file explains the layout of your LED strips in 2D space. This is used to pre-calculate some important information, speeding up complex draw calls.

Example config file:

center: (0.0, 0.5)
density: 30.0
--segments--
(-2, 0) --> (0.5, -1) --> (3.5, 0) -->
(2, 2) --> (-2, 2) --> (-2, 0)

For more information on how to write config files in this format, check out the docs.

Drawing

Once you have your Sled struct, you can start drawing to it right away! Here’s a taste of some of the things Sled lets you do:

Set all vertices to white:

sled.set_vertices(Rgb::new(1.0, 1.0, 1.0));

Note that this is a custom terminal UI visualization that is not packaged as part of the sled library. It is ultimately up to you to decide how to visualize your LEDs; Sled just handles the computation.

Set all LEDs 2 units away from the center_point to red:

sled.set_at_dist(2.0, Rgb::new(1.0, 0.0, 0.0));
// or relative to any other point using:
// sled.set_at_dist_from(distance, pos, color)

Set each LED using a function of its direction from point (2, 1):

sled.map_by_dir_from(Vec2::new(2.0, 1.0), |dir| {
    let red = (dir.x + 1.0) * 0.5;
    let green = (dir.y + 1.0) * 0.5;
    Rgb::new(red, green, 0.5)
});

Dim one of the walls by 75%:

sled.modulate_segment(3, |led| led.color * 0.25)?;

Set all LEDs within the overlapping areas of two different circles to blue:

let circle_1: Filter = sled.within_dist_from(
    2.0,
    Vec2::new(1.0, 0.5)
);
    
let circle_2: Filter = sled.within_dist_from(
	2.5,
	Vec2::new(-1.0, 1.5)
);

let overlap = circle_1.and(&circle_2);
sled.set_filter(&overlap, Rgb::new(0.0, 0.0, 1.0));

For more examples, see the documentation comments on the Sled struct.

Output

Once you’re ready to display these colors, you’ll probably want them packed in a nice contiguous array of RGB values. There are a few methods available to pack the information you need.

let colors_f32 = sled.colors();
// An Iterator of Rgbs, 32-bits/channel

for color in colors_f32 {
    let red: f32 = color.red;
    // -snip- //
}

A few other handy output methods:

let leds = sled.leds();
// An Iterator of Led structs (holds color, position, distance/angle relative from center, etc)

let colors_u8 = sled.colors_coerced::<u8>();
// An Iterator of Rgbs, 8-bits/channel

let positions = sled.positions();
// An Iterator of Vec2s, representing the position of each LED

let colors_f32_and_positions = sled.colors_and_positions();
// An Iterator of (Rgb, Vec2) tuple pairs representing each LEDs color and position.

let colors_f32_and_positions = sled.colors_and_positions_coerced::<u8>();
// An Iterator of (Rgb<u8>, Vec2) tuple pairs representing each LEDs color and position.

Advanced Features

For basic applications, the Sled struct gives you plenty of power. Odds are though, you'll want to create more advanced effects that might be time or user-input driven. A few optional (enabled by default, opt-out by disabling their compiler features) tools are provided to streamline that process.

Drivers

Drivers are useful for encapsulating everything you need to drive a lighting effect all in one place. Here's an example of what a simple one might look like:

let mut driver = Driver::new();
use spatial_led::driver_macros::*;

driver.set_startup_commands(|_sled, buffers, _filters| {
    let colors = buffers.create_buffer::<Rgb>("colors");
    colors.extend([
        Rgb::new(1.0, 0.0, 0.0),
        Rgb::new(0.0, 1.0, 0.0),
        Rgb::new(0.0, 0.0, 1.0),
    ]);
    Ok(())
});

driver.set_draw_commands(|sled, buffers, _filters, time_info| {
    let elapsed = time_info.elapsed.as_secs_f32();
    let colors = buffers.get_buffer::<Rgb>("colors")?;
    let num_colors = colors.len();
    // clear our canvas each frame
    sled.set_all(Rgb::new(0.0, 0.0, 0.0));

    for i in 0..num_colors {
        let alpha = i as f32 / num_colors as f32;
        let angle = elapsed + (2.0 * PI * alpha);
        sled.set_at_angle(angle, colors[i]);
    }
    Ok(())
});

To start using the Driver, give it ownership over a Sled using .mount() and use .step() to manually refresh it.

let sled = Sled::new("path/to/config.yap")?;
driver.mount(sled); // sled gets moved into driver here.

loop {
    driver.step();
    let colors = driver.colors();
    // display those colors however you want
}

.set_startup_commands() - Define a function or closure to run when driver.mount() is called. Grants mutable control over Sled, BufferContainer, and Filters.

set_draw_commands() - Define a function or closure to run every time driver.step() is called. Grants mutable control over Sled, and immutable access to BufferContainer, Filters, and TimeInfo.

set_compute_commands() - Define a function or closure to run every time driver.step() is called, scheduled right before draw commands. Grants immutable access to Sled, mutable control over BufferContainer and Filters and immutable access to TimeInfo.

If you need to retrieve ownership of your sled later, you can do:

let sled = driver.dismount();

If you don't need Drivers for your project, you can shed a dependency or two by disabling the drivers compiler feature.

For more examples of ways to use drivers, see the driver_examples folder in the spatial_led_examples repository.

Driver Macros

Some macros have been provided to make authoring drivers a more ergonomic experience. You can apply the following attributes to functions that you want to use for driver commands:

• #[startup_commands]
• #[compute_commands]
• #[draw_commands]

Using these, you can express your commands as a function that only explicitly states the parameters it needs. The previous example could be rewritten like this, for example:

use spatial_led::driver_macros::*;
use spatial_led::{BufferContainer, SledResult, TimeInfo};

#[startup_commands]
fn startup(buffers: &mut BufferContainer) -> SledResult {
    let colors = buffers.create_buffer::<Rgb>("colors");
    colors.extend([
        Rgb::new(1.0, 0.0, 0.0),
        Rgb::new(0.0, 1.0, 0.0),
        Rgb::new(0.0, 0.0, 1.0),
    ]);
    Ok(())
}

#[draw_commands]
fn draw(sled: &mut Sled, buffers: &BufferContainer, time_info: &TimeInfo) -> SledResult {
    let elapsed = time_info.elapsed.as_secs_f32();
    let colors = buffers.get_buffer::<Rgb>("colors")?;
    let num_colors = colors.len();
    // clear our canvas each frame
    sled.set_all(Rgb::new(0.0, 0.0, 0.0));

    for i in 0..num_colors {
        let alpha = i as f32 / num_colors as f32;
        let angle = elapsed + (2 * PI * alpha);
        sled.set_at_angle(angle, colors[i])?;
    }
    Ok(())
}

//--snip--//

let mut driver = Driver::new();
driver.set_startup_commands(startup);
driver.set_draw_commands(draw));

Buffers

A driver exposes a data structure called BufferContainer. A BufferContainer essentially acts as a HashMap of &str keys to Vectors of any type you choose to instantiate. This is particularly useful for passing important data and settings in to the effect.

It's best practice to create buffers with startup commands, and then modify them either through compute commands or from outside the driver depending on your needs.

#[startup_commands]
fn startup(sled: &mut Sled, buffers: &mut BufferContainer) -> SledResult {
    let wall_toggles: &mut Vec<bool> = buffers.create_buffer("wall_toggles");
    let wall_colors: &mut Vec<Rgb> = buffers.create_buffer("wall_colors");
    let some_important_data = buffers.create_buffer::<MY_CUSTOM_TYPE>("important_data");
    Ok(())
}

driver.set_startup_commands(startup);

To access buffers from outside driver, just do:

let buffers: &BufferContainer = driver.buffers();
// or
let buffers: &mut BufferContainer = driver.buffers_mut();

Using a BufferContainer is relatively straightforward.

let draw_commands = |sled, buffers, _, _| {
    let wall_toggles = buffers.get_buffer::<bool>("wall_toggles")?;
    let wall_colors = buffers.get_buffer::<Rgb>("wall_colors")?;
    let important_data = buffers.get_buffer::<MY_CUSTOM_TYPE>("important_data")?;

    for i in 0..wall_toggles.len() {
        if wall_toggles[i] == true {
            sled.set_segment(i, wall_colors[i])?;
        } else {
            sled.set_segment(i, Rgb::new(0.0, 0.0, 0.0))?;
        }
    }
    
    Ok(())
}

If you need to mutate buffer values:

// Mutable reference to the whole buffer
let buffer_mut = buffers.get_buffer_mut::<bool>("wall_toggles")?;

// Modify just one item
buffers.set_buffer_item("wall_toggles", 1, false)?;

// Mutable reference to just one item
let color: &mut Rgb = buffers.get_buffer_item_mut("wall_colors", 2)?;
*color /= 2.0;

Filters

For exceptionally performance-sensitive scenarios, Filters can be used to predefine important LED regions. They act as sets, containing only the indicies of the LEDs captured in the set. When we want to perform an operation on that set, we pass the Filter back to the Sled like this:

let all_due_north: Filter = sled.at_dir(Vec2::new(0.0, 1.0));
sled.for_each_in_filter(&all_due_north, |led| {
    led.color = Rgb::new(1.0, 1.0, 1.0);
});

Note that other methods exist like .set_filter(filter, color), .modulate_filter(filter, color_rule), and .map_filter(filter, map)

The Filters struct provided by Driver is basically a hashmap of &str keys to Sled Filter structs. Using this, we can pre-compute important sets and then store them to the driver for later usage.

A slightly better example would be to imagine that we have an incredibly expensive mapping function that will only have a visible impact on the LEDs within some radius $R$ from a given point $P$. Rather than checking the distance of each LED from that point every frame, we can instead do something like this:

let startup_commands = |sled, buffers, filters| {
    let area: Filter = sled.within_dist_from(5.0, Vec2::new(-0.25, 1.5));

    filters.set("area_of_effect", area);
    Ok(())
};

let draw_commands = |sled, buffers, filters, _| {
    let area_filter = filters.get("area_of_effect")?;
    sled.map_filter(area_filter, |led| {
        // expensive computation
    });
    Ok(())
};

Most .get methods on sled will return a Filter, but if you need more precise control you can do something like this:

let even_filter = sled.filter(|led| led.index() % 2 == 0);

I imagine this feature will get less love than buffers, but I can still see a handful of scenarios where this can be very useful for some users. In a future version this may become an opt-in compiler feature.

Scheduler

The Scheduler struct makes it super easy to schedule redraws at a fixed rate.

let mut scheduler = Scheduler::new(120.0);

scheduler.loop_forever(|| {
    driver.step();
});

Scheduler, by default, utilizes spin_sleep to minimize the high CPU usage you typically see when you spin to wait for the next update by default.

Here are a few other methods that you might also consider:

// loops until false is returned
scheduler.loop_while_true(|| {
    // -snip- //
    return true;
});

// loops until an error of any type is returned
scheduler.loop_until_err(|| {
    // -snip- //
    Ok(())
});

// best for times when you don't want to pass everything through a closure
loop {
    // -snip- //
    scheduler.sleep_until_next_frame();
}

You can define your own CustomScheduler backed by whatever sleeping method you prefer if you wish. If you'd like to trim away the spin_sleep dependency, you can also disable the spin_sleep feature flag.

If you don't need the Scheduler struct in general, you can disable the scheduler and spin_sleep flags.

no_std Support

Spatial LED is now usable in no_std environments as of 0.2.0 (though alloc is still required), thanks to some awesome contributions by Claudio Mattera.

To do this, disable the std flag and enable the libm flag (for use by glam and palette).

Users on the nightly toolchain can also enable the core-simd feature flag for some extra performance if you know your target platform supports SIMD instructions.

Drivers

The default Driver implementation depends on std::time::Instant to track elapsed time between driver steps. For no_std environments, you must provide your own struct that implements the crate::time::Instant trait.

Once you have that, building a CustomDriver becomes as easy as:

use spatial_led::driver::CustomDriver;

let mut driver = CustomDriver<MyCustomInstant>::new();
driver.mount(sled);

Schedulers

Similarly, the default Scheduler relies on Instants, as well as methods only available through the standard library to handle sleeping. Thus, to build a Scheduler in no_std environments, you'll need to provide custom implementations of the spatial_led::time::Instant and spatial_led::time::Sleeper traits.

use spatial_led::driver::CustomDriver;

let scheduler = CustomScheduler<MyCustomInstant, MyCustomSleeper>::new(120.0);

 scheduler.loop_forever(|| {
     println!("tick!");
 });

As embassy is gaining popularity in the embedded Rust scene, Claudio has also provided an async interface via the AsyncCustomScheduler struct.

Feedback and Contributions

The author of this crate does not own any hardware that would allow him test spatial_led on real no_std environments, so bug reports and PRs are very appreciated!

Feature Flags

Enabled by Default:

• std
• drivers : Enables Drivers
• scheduler : Enables Schedulers
• spin_sleep : If std is enabled, sets the default Scheduler to use spin_sleep to schedule tasks.

Opt-in:

• named_colors : Exposes color constants (for example spatial_led::color::consts::WHITE)
• libm : Needed for some no_std environments.
• core-simd (Nightly) : Allows the vector math library used by the crate to take advantage of SIMD instructions when std::simd isn't available.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.