cloudiful-bevy-outline

Small reusable Bevy outline helper crate for geometry-shell outlines.

What it provides

GpmoOutlinePlugin: initializes default outline assets
GpmoOutlinePlugin::with_default_style(...): installs a custom default outline style
OutlineStyle: configurable color, emissive strength, and shell scale
OutlineAssets: default cached material/style resource
OutlineShell: marker component for spawned outline meshes
create_outline_material(...): build a custom outline material from an OutlineStyle
outline_shell_transform(...): build the transform used for shell scaling
spawn_outline_mesh(...): attach an outline mesh with a custom material/style
spawn_default_outline_mesh(...): attach an outline mesh using the plugin's default style

What it does not provide

screen-space outlines
stencil-based outline passes
automatic mesh duplication for arbitrary scenes

This crate intentionally stays simple: it supports the common "draw a slightly enlarged backface-only shell" outline technique.

Usage

Add the plugin:

use bevy::prelude::*;
use cloudiful_bevy_outline::{GpmoOutlinePlugin, OutlineAssets};

let mut app = App::new();
app.init_resource::<Assets<StandardMaterial>>()
    .add_plugins(GpmoOutlinePlugin::default());
app.update();

assert!(app.world().contains_resource::<OutlineAssets>());

Spawn an outline child with the default material/style resource:

use bevy::prelude::*;
use cloudiful_bevy_outline::{OutlineAssets, spawn_default_outline_mesh};

fn attach_outline(
    parent: &mut ChildSpawnerCommands,
    outline_assets: &OutlineAssets,
    mesh: Handle<Mesh>,
) {
    spawn_default_outline_mesh(parent, outline_assets, mesh, Visibility::Hidden);
}

Then toggle the outline child's Visibility.

The full runnable example lives at examples/basic.rs.

Default Style Flow

GpmoOutlinePlugin creates one default material at startup and stores it in OutlineAssets.

use OutlineAssets when many outline shells can share one default look
use GpmoOutlinePlugin::with_default_style(...) when the whole app should start with a different default style
use create_outline_material(...) when one outline needs its own material
use outline_shell_transform(...) when you need the shell scale without spawning through the helper

Custom style example:

use bevy::prelude::*;
use cloudiful_bevy_outline::{GpmoOutlinePlugin, OutlineAssets, OutlineStyle};

let mut app = App::new();
app.init_resource::<Assets<StandardMaterial>>()
    .add_plugins(GpmoOutlinePlugin::with_default_style(OutlineStyle {
        color: Color::srgb(1.0, 0.6, 0.2),
        emissive_strength: 3.0,
        scale: Vec3::splat(1.12),
    }));
app.update();

let outline_assets = app.world().resource::<OutlineAssets>();
assert_eq!(outline_assets.default_style().emissive_strength, 3.0);

Technique

This crate uses a geometry-shell outline: