Particle Emitter

The Particle Emitter is the primary particle-spawning node within a Particle System. It defines where, how, and with what properties particles are born. Each emitter produces a stream of particles according to its configuration — shape, velocity, spawn rate, lifetime, size, color, physics, and visual type. Multiple emitters can coexist inside a single Particle System to create layered effects.

The Emitter uses a modular connection system: instead of exposing dozens of ports directly, it accepts configuration structures from dedicated helper nodes — Particle Shape, Particle Velocity, Particle Spawn, and Particle Type — via structure input ports. When these are not connected, sensible defaults are used (point shape, radial velocity at 0.2 speed, continuous emission at 100 particles/second, billboard rendering).

The Emitter also drives the trigger system: particles can emit events On Death, On Collision, or On Lifetime, which cascade to other emitters via the Trigger input for chain-reaction effects like fireworks or explosions.

Modular Configuration

The Emitter's behavior is configured through four structure input ports, each accepting output from a dedicated helper node:

1. Shape (from Particle Shape) — Where particles spawn: point, line, circle, sphere, box, cone, rectangle, hemisphere, torus, or cylinder. Each shape supports spawn modes (fill/outline for 2D; volume/surface/edges for 3D).

1. Velocity (from Particle Velocity) — How particles move initially: away from center, in a specific direction, or randomly. Controls speed, variance, spread angle, and velocity inheritance from emitter movement.

1. Spawn (from Particle Spawn) — When and how many particles are emitted: continuously at a rate, in bursts with delay and loops, or on external trigger events.

1. Type (from Particle Type) — How particles look: billboard quads, velocity-stretched sprites, pixel points, SDF circles, trails, 3D cubes with PBR, or 3D spheres with PBR. Each mode has its own blend mode, texture, and material options.

Color and Size Over Life

Particles interpolate from Color to Color End through an 8-stop gradient over their lifetime. The color transition is smooth and continuous. Similarly, if Size End > 0, particles scale from Size to Size End linearly. Custom size-over-life and opacity-over-life curves can be set via the inspector (stored in customStorage).

Trigger System (Cascading Events)

The trigger system enables particle chain reactions:

1. Enable trigger outputs on the source Emitter via the inspector (Trigger on Death, Trigger on Collision, or Trigger on Lifetime Threshold).
2. The GPU flags particles for events as they die, collide, or cross the lifetime threshold.
3. Events are read back asynchronously (one-frame latency) and routed to the Emitter's output ports.
4. Connect an output (e.g., On Death) to another Emitter's Trigger input.
5. Set the receiving Emitter's Spawn mode to Trigger (via a Particle Spawn node).
6. Each event spawns a burst of particles at the event position, inheriting the source particle's velocity.

This allows firework-style effects where one particle's death spawns dozens of child particles, which can in turn trigger further generations.

Emitter Velocity Inheritance

When an emitter moves (Position changes over time), the system tracks its velocity. The Inherit Velocity parameter on the Particle Velocity node controls how much of the emitter's movement velocity is added to newly spawned particles. At 0, particles ignore emitter motion; at 1, particles fully inherit it.

• Single emitter for simple effects (rain, snow, sparks)
• Multiple emitters at different positions for complex scenes
• Cascading emitters using the trigger system for fireworks, explosions, or chain reactions
• Moving emitters (animate Position) with velocity inheritance for comet trails
• Emissive particles combined with system bloom for neon glow effects

• Connect Shape, Velocity, Spawn, and Type nodes to the Emitter for full control. Without them, you get a basic point emitter with radial velocity.
• Color End alpha defaults to 0, which makes particles fade out naturally over their lifetime. Set alpha to 1 for particles that remain fully opaque until death.
• Use Lifetime Variance to prevent all particles from dying at the same time, which looks more natural.
• Gravity stacks with Particle Field forces. Use the Emitter's Gravity for simple downward pull and Fields for complex force patterns.
• The trigger system has one-frame latency. For fast chain reactions, keep particle lifetimes short on intermediate emitters.
• Collision Spread > 0 scatters sub-emitter spawns around the collision point, creating more organic-looking cascading effects.