Derive Macro ParticleType 

#[derive(ParticleType)]

Derive macro for particle type enums.

Creates type-safe particle categories that convert to/from u32 for GPU usage. Variants are assigned sequential IDs starting from 0.

Generated Items

For an enum Species:

• impl From<Species> for u32 - Convert variant to integer
• impl From<u32> for Species - Convert integer to variant (invalid values default to first variant)
• Species::count() -> u32 - Returns number of variants

Requirements

• Must be an enum (not a struct)
• All variants must be unit variants (no fields)
• Enum should also derive Clone, Copy, PartialEq for typical usage

Example

#[derive(ParticleType, Clone, Copy, PartialEq)]
enum Species {
    Prey,      // = 0
    Predator,  // = 1
    Plant,     // = 2
}

// Convert to u32 for rules
let prey_id: u32 = Species::Prey.into();  // 0

// Use with typed rules
Rule::Chase {
    self_type: Species::Predator.into(),
    target_type: Species::Prey.into(),
    radius: 0.3,
    strength: 2.0,
}

// Use in spawner
Creature {
    position: pos,
    velocity: Vec3::ZERO,
    particle_type: Species::Prey.into(),
}

// Get variant count
let num_species = Species::count();  // 3

Panics

The macro panics at compile time if:

• Applied to a struct instead of an enum
• Any variant has fields (tuple or struct variants)
• Enum has zero variants