Projectiles

A projectile is an entity carrying an SProjectileComponent. SProjectileSystem sweeps it forward every frame with a continuous cast, so it never tunnels through thin walls, reports its first hit, and despawns after its lifetime.

This is far cheaper than a full rigid body and runs entirely in the ECS, so prefer it for bullets and thrown objects that only need to know what they hit.

Spawning one

SpawnProjectile lives on CWorld and takes the same arguments in both languages: an origin, a world-space velocity, damage, a lifetime, and optionally the entity that fired it.

entt::entity Shot = World->SpawnProjectile(Muzzle, Aim * 60.0f, 25.0f, 5.0f, Shooter);

World->GetRegistry().get<SProjectileComponent>(Shot).OnHit.AddLambda(
    [](const SProjectileHitEvent& Hit)
    {
        LOG_INFO("hit {} at {} for {}", (uint32)Hit.HitEntity, Hit.Point, Hit.Damage);
    });

public sealed class Gun : EntityScript
{
    private void Fire(FVector3 Muzzle, FVector3 Aim)
    {
        Entity Shot = World.SpawnProjectile(Muzzle, Aim * 60.0f, damage: 25.0f, lifetime: 5.0f);
        World.Registry.Get<SProjectileComponent>(Shot).OnHit.Bind(OnProjectileHit);
    }

    private void OnProjectileHit(SProjectileHitEvent Hit)
    {
        Debug.Log($"hit {Hit.HitEntity} at {Hit.Point} for {Hit.Damage}");
    }
}

The overload without an instigator defaults Damage to 0 and Lifetime to 5 seconds. Passing an instigator makes the sweep ignore that entity, so a projectile never hits whoever fired it.

Tuning the component

You can also add SProjectileComponent to an entity yourself, in the editor under Gameplay, and set these directly.

Field	Meaning
`Velocity`	World-space velocity (m/s)
`GravityScale`	Multiplier on world gravity; 0 = a straight line
`Radius`	Sweep radius; 0 = a thin ray, larger for a fatter projectile
`Damage`	Carried in the hit event; you decide how to apply it
`CollisionMask`	Which collision layers it can hit, default Static + Dynamic
`bDestroyOnHit`	Destroy the projectile on its first hit
`Instigator`	Entity the sweep ignores (the shooter)
`OnHit`	Fired once on hit, with an `SProjectileHitEvent`

SProjectileHitEvent carries Projectile, HitEntity, Point, Normal, and Damage.