Bevy Jam 5, Radiance Cascades, and Calculators in many ui kits

Bevy Jam 5 is underway! If you haven't joined in yet you still have a whole week so head on over to Itch.io and join the jam.

We've got a whole bunch to cover this week including some exciting crate releases that, if you ask me, were motivated by Bevy Jam 5, and a number of full open source games and releases.

We'll start off as usual covering some project ongoings and merges before getting deeper into the ecosystem and even seeing a 3D editor for Mario Kart Wii tracks.

Observers

Observers are brand new in Bevy 0.14 but their implementation in that release is considered the "first" implementation. With that in mind we're already starting to see Observers evolve further with Event Bubbling, a new OnReplaced event and allowing Observer systems to have outputs;

If you're still looking for a Hooks and Observers overview, check out this video which is mentioned later in this issue.

Unofficial Bevy Meetup 5

Bevy Meetup #5 was livestreamed just before Bevy Jam #5 with two talks.

• Florian - Truck Instrument Cluster powered by Bevy
• Spencer - Compute centric vector graphics with bevy_vello

Calculating UI Toolkits

There are many implementations of UI toolkit in progress these days, which means picking one could be a decision on your list. Over the last week a number of different toolkit authors have built out Calculator examples.

• haalka
• bevy_ui
• bevy_cobweb_ui
• bevy_lunex

The first calculator example is here in the #ui channel in the Bevy Discord, and there's some good discussion from framework authors detailing the different approaches and priorities of crates like sickle_ui and quill.

Radiance Cascades

Radiance Cascades are an interesting global illumination technique that have been gaining interest over the last few weeks after a YouTube video was released talking about them.

While the video was recent, the paper (YouTube link) was released almost a year ago which has resulted in useful visualizations of the technique, fancy demos, and articles having been written about it. There's a lot of information about them these days.

bevy_flatland_radiance_cascades and bevy_radiance_cascades are a couple of recent implementations in Bevy.

While there have been other research-level efforts over the last year such as bevy_ridiculous_ssgi, 3d Radiance Cascades don't seem to work out as well as 2d, but the technique is great for 2d.

wgpu goes major

release notes - reddit

wgpu got its first major release, starting with v22.0.0 which follows on from the previous 0.21.0. This is notably not a "stable 1.0 release" but reflects the fact that wgpu has been used in production by many projects including Bevy, and powers the implementation of the WebGPU API in Servo, Firefox, and JavaScript for Deno.

It is a well-known fact that WGPU has been used for applications and platforms already in production for years, at this point. We are often concerned with tracking breaking changes, and affecting these consumers' ability to ship. By releasing our first major version, we publicly acknowledge that this is the case.

Naming closure systems

14369 introduces a new API to enable renaming closure-based systems, which allows them to show up in tooling as named item rather than ::{closure}. This will show most often in tools like bevy_mod_debugdump and tracing.

app
    .add_systems(Startup, IntoSystem::into_system(|name: SystemName| {
        println!("System name: {}", name.name().to_owned());
    }).with_name("print_test_system"));

Isometries

#14269 introduces the concept of Isometry types into the bevy_math. Isometries represent rigid motion in two and three dimensions such as translation and rotation but not reflection. If you want to learn more about them, check out the follow up PR with adds some more examples to what can feel like a very abstract concept.

One common operation is to compute an isometry representing the relative positions of two objects for things like intersection tests. This can be done with an inverse transformation:

use bevy_math::{Isometry2d, Rot2, Vec2};

let circle_iso = Isometry2d::from_translation(Vec2::new(2.0, 1.0));
let rectangle_iso = Isometry2d::from_rotation(Rot2::degrees(90.0));

// Compute the relative position and orientation between the two shapes
let relative_iso = circle_iso.inverse() * rectangle_iso;

// Or alternatively, to skip an extra rotation operation:
let relative_iso = circle_iso.inverse_mul(rectangle_iso);

Cyclic Splines

14106 introduced a new trait CyclicCubicGenerator to power the generation of cyclic curves through control points. This trait is implemented for a number of different types including CubicHermite, CubicCardinalSpline, CubicBSpline, and LinearSpline.

plugin_group! macro

14339 introduced a new plugin_group! macro which is a more restrictive version of building a custom PluginGroup but provides some nice wins in terms of keeping documentation up to date. This is the same trait that DefaultPlugins and MinimalPlugins implement.

Built in PostProcessing stack

#13695 introduces a new built-in postprocessing shader that's design to hold miscellaneous postprocessing effects. It then continues to start with chromatic aberration as the first effect. The effect is usable through adding ChromaticAberration to your camera.

The PR, as is usual with pcwalton's effects, is well documented, explained, and comes with a new usage example: post_processing. I highly suggest checking this PR out if you're interested in how Bevy's rendering systems work.

Localized Volumetric Fog

#14099

Currently, volumetric fog is global and affects the entire scene uniformly. This is inadequate for many use cases, such as local smoke effects. To address this problem, this commit introduces fog volumes, which are axis-aligned bounding boxes (AABBs) that specify fog parameters inside their boundaries. Such volumes can also specify a density texture, a 3D texture of voxels that specifies the density of the fog at each point.

A new example, fog_volumes, has been added. It demonstrates a single fog volume containing a voxelized representation of the Stanford bunny. The existing volumetric_fog example has been updated to use the new local volumetrics API.

Alice's Merge Train is a maintainer-level view into active PRs, both those that are merging and those that need work. There's 38 PRs this week!