berdicles

Expressive CPU particle system for the bevy engine.

Feature Set

• Instancing based CPU particles.
• Expressive non-physics based particle traits.
• Familiar setup with bevy's native Material and Mesh.
• Particles as emitters.
• Mesh based particle trails.
• Particle events that spawn other particles.
• Multiple renders from the same simulation result via ParticleRef.
• Billboard particles.

Non-features

• GPU simulation.
• SIMD and similar optimizations.
• First party physics support.

Getting Started

Add a ParticleSystemBundle, which is a MaterialMeshBundle with a ParticleInstance.

• Huh?

First we need to add ParticleMaterialPlugin, not MaterialPlugin, which sets up a different render pipeline.

We only use vertex_shader() and fragment_shader() from Material so the rest can be ignored.

This uses the mesh as the particle shape and the shader for instancing. The StandardParticle is already setup in this crate, but you can define your own Material by referencing this shader's source code.

To create a ParticleInstance we need a ParticleSystem trait implementor and a Particle that it spawns.

Trait Based Particles

Physics based particles is commonly seen in most particle system implementations, but they might be frustrating to work with in some situations. We provide alternative ways to implement particles, instead of defining things as velocities, forces or curves.

impl Particle for SpiralParticle {
    fn update(&mut self, dt: f32) { 
        self.lifetime += dt;
    }

    fn get_transform(&self) -> Transform {
        Transform::from_translation(
            Vec3::new(self.lifetime, 0., 0.)
        ).with_rotation(
            Quat::from_rotation_y(self.lifetime)
        )
    }

    fn expiration_state(&self) -> ExpirationState{
        ExpirationState::explode_if(self.lifetime > 8.)
    }
}

Sub-particle Systems

SubParticleSystem uses a parent particle system's particles as spawners for other particles.

• Add ParticleParent(Entity) to point to a parent
• Add the downcast function as_sub_particle_system to your ParticleSystem implementation.

Yes you can chain these infinitely.

Event Particle Systems

EventParticleSystem can listen to events like particle despawning or colliding and spawn particles on events.

• Add ParticleParent(Entity) to point to a parent
• Add ParticleEventBuffer to the parent to record these events,
• Add the downcast function as_event_particle_system to your ParticleSystem implementation.

Trail Rendering

We can render trails behind particles as mesh.

• Implement TrailedParticle on your particle.
• Add on_update, detach_slice and as_trail_particle_system to your ParticleSystem implementation.
• Add TrailMeshOf(Entity) to a MaterialMeshBundle to render them.

Versions

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.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.