Struct SubEmitter 

pub struct SubEmitter {
    pub parent_type: u32,
    pub child_type: u32,
    pub count: u32,
    pub speed_min: f32,
    pub speed_max: f32,
    pub spread: f32,
    pub inherit_velocity: f32,
    pub child_lifetime: Option<f32>,
    pub child_color: Option<Vec3>,
    pub spawn_radius: f32,
    pub trigger: SpawnTrigger,
}

Configuration for a sub-emitter that spawns children when triggered.

Example

SubEmitter::new(ParentType, ChildType)
    .count(20)                    // Spawn 20 children per death
    .speed(1.0..2.0)              // Random speed in range
    .spread(PI / 4.0)             // 45-degree cone
    .inherit_velocity(0.5)        // 50% of parent velocity
    .child_lifetime(1.5)          // Children live 1.5 seconds
    .child_color(Vec3::new(1.0, 0.5, 0.0))  // Orange children

Fields

parent_type: u32

Parent particle type that triggers sub-emission.

child_type: u32

Child particle type to spawn.

count: u32

Number of children to spawn per trigger event.

speed_min: f32

Speed range for children (random within range).

speed_max: f32

spread: f32

Spread angle in radians (0 = laser, PI = hemisphere, TAU = full sphere).

inherit_velocity: f32

How much of parent’s velocity children inherit (0.0 - 1.0).

child_lifetime: Option<f32>

Optional fixed lifetime for children (overrides any lifecycle rules).

child_color: Option<Vec3>

Optional fixed color for children.

spawn_radius: f32

Spawn radius around parent position.

trigger: SpawnTrigger

What triggers this sub-emitter (death, condition, etc.).

Implementations

impl SubEmitter

pub fn new(parent_type: u32, child_type: u32) -> Self

Create a new sub-emitter configuration.

By default, triggers on parent death. Use .on_condition() to trigger on a custom WGSL condition instead.

Arguments

• parent_type - Type of particle that triggers sub-emission
• child_type - Type of particle to spawn as children

Example

// Classic death-triggered spawning (fireworks)
SubEmitter::new(Firework::Rocket.into(), Firework::Spark.into())

// Condition-triggered spawning (cell division)
SubEmitter::new(Cell::Parent.into(), Cell::Child.into())
    .on_condition("p.energy > 1.5")
    .count(2)

pub fn on_condition(self, condition: impl Into<String>) -> Self

Set the trigger to a custom WGSL condition.

The condition is a WGSL boolean expression with access to:

• p - The current particle
• uniforms.time - Total elapsed time
• uniforms.delta_time - Frame delta time

When the condition evaluates to true, spawn events are recorded and children are spawned in a secondary pass.

Example

// Spawn when energy exceeds threshold
SubEmitter::new(Parent, Child)
    .on_condition("p.energy > 0.9")
    .count(3)

// Periodic spawning (approximately every second)
SubEmitter::new(Parent, Child)
    .on_condition("fract(p.age) < uniforms.delta_time")
    .count(1)

// Spawn near the origin
SubEmitter::new(Parent, Child)
    .on_condition("length(p.position) < 0.2")
    .count(2)

pub fn trigger(self, trigger: SpawnTrigger) -> Self

Set the trigger type explicitly.

Example

SubEmitter::new(Parent, Child)
    .trigger(SpawnTrigger::OnDeath)

pub fn count(self, n: u32) -> Self

Set the number of children to spawn per parent death.

Example

SubEmitter::new(Rocket, Spark).count(50)

pub fn speed(self, range: Range<f32>) -> Self

Set the speed range for children.

Children will have a random speed within this range.

Example

SubEmitter::new(Rocket, Spark).speed(1.0..3.0)

pub fn spread(self, radians: f32) -> Self

Set the spread angle in radians.

• 0 = All children move in same direction (laser)
• PI/4 = 45-degree cone
• PI/2 = 90-degree cone (hemisphere)
• PI = Full hemisphere
• TAU = Full sphere (all directions)

Example

SubEmitter::new(Rocket, Spark).spread(std::f32::consts::PI)

pub fn inherit_velocity(self, factor: f32) -> Self

Set how much of parent’s velocity children inherit.

• 0.0 = Children ignore parent velocity
• 0.5 = Children inherit half of parent velocity
• 1.0 = Children inherit full parent velocity

Example

SubEmitter::new(Rocket, Spark).inherit_velocity(0.5)

pub fn child_lifetime(self, seconds: f32) -> Self

Set a fixed lifetime for children.

This overrides any Rule::Lifetime for child particles. If not set, children follow normal lifecycle rules.

Example

SubEmitter::new(Rocket, Spark).child_lifetime(1.5)

pub fn child_color(self, color: Vec3) -> Self

Set a fixed color for children.

If not set, children inherit parent’s color.

Example

SubEmitter::new(Rocket, Spark).child_color(Vec3::new(1.0, 0.8, 0.0))

pub fn spawn_radius(self, radius: f32) -> Self

Set spawn radius around parent position.

Children spawn at random positions within this radius of the parent.

Example

SubEmitter::new(Rocket, Spark).spawn_radius(0.1)

Trait Implementations

impl Clone for SubEmitter

fn clone(&self) -> SubEmitter

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for SubEmitter

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.