I'm running into an issue with collisions between two entities with a character controller component. In the collision handler for moveCharacter the collision has both hitEntity and characterEntity set to the same object. This object is the entity that was moved with moveCharacter()
The below example configures 3 objects.
stationary sphere with character controller
falling sphere with character controller
a stationary cube with a collision component
if the falling sphere hits the stationary sphere then the collision handler reports both hitEntity and characterEntity to be the falling sphere. I would expect that the hitEntity would be the stationary sphere and the character entity would be the falling sphere.
if the falling sphere hits the cube with a collision component the the hit entity is the cube and the characterEntity is the falling sphere as expected.
Is this the expected behavior? The entities act as expected visually however if I want the spheres to react differently depending on what character they collided with then I am not getting the expected results. IE: If a player controlled character collides with a NPC then exchange resource with NPC. if player collides with enemy then take damage.
import SwiftUI
import RealityKit
struct ContentView: View {
@State var root: Entity = Entity()
@State var stationary: Entity = createCharacter(named: "stationary", radius: 0.05, color: .blue)
@State var falling: Entity = createCharacter(named: "falling", radius: 0.05, color: .red)
@State var collisionCube: Entity = createCollisionCube(named: "cube", size: 0.1, color: .green)
//relative to root
@State var fallFrom: SIMD3<Float> = [0,0.5,0]
var body: some View {
RealityView { content in
content.add(root)
root.position = [0,-0.5,0.0]
root.addChild(stationary)
stationary.position = [0,0.05,0]
root.addChild(falling)
falling.position = fallFrom
root.addChild(collisionCube)
collisionCube.position = [0.2,0,0]
collisionCube.components.set(InputTargetComponent())
}
.gesture(SpatialTapGesture().targetedToAnyEntity().onEnded { tap in
let tapPosition = tap.entity.position(relativeTo: root)
falling.components.remove(FallComponent.self)
falling.teleportCharacter(to: tapPosition + fallFrom, relativeTo: root)
})
.toolbar {
ToolbarItemGroup(placement: .bottomOrnament) {
HStack {
Button("Drop") {
falling.components.set(FallComponent(speed: 0.4))
}
Button("Reset") {
falling.components.remove(FallComponent.self)
falling.teleportCharacter(to: fallFrom, relativeTo: root)
}
}
}
}
}
}
@MainActor
func createCharacter(named name: String, radius: Float, color: UIColor) -> Entity {
let character = ModelEntity(mesh: .generateSphere(radius: radius), materials: [SimpleMaterial(color: color, isMetallic: false)])
character.name = name
character.components.set(CharacterControllerComponent(radius: radius, height: radius))
return character
}
@MainActor
func createCollisionCube(named name: String, size: Float, color: UIColor) -> Entity {
let cube = ModelEntity(mesh: .generateBox(size: size), materials: [SimpleMaterial(color: color, isMetallic: false)])
cube.name = name
cube.generateCollisionShapes(recursive: true)
return cube
}
struct FallComponent: Component {
let speed: Float
}
struct FallSystem: System{
static let predicate: QueryPredicate<Entity> = .has(FallComponent.self) && .has(CharacterControllerComponent.self)
static let query: EntityQuery = .init(where: predicate)
let down: SIMD3<Float> = [0,-1,0]
init(scene: RealityKit.Scene) {
}
func update(context: SceneUpdateContext) {
let deltaTime = Float(context.deltaTime)
for entity in context.entities(matching: Self.query, updatingSystemWhen: .rendering) {
let speed = entity.components[FallComponent.self]?.speed ?? 0.5
entity.moveCharacter(by: down * speed * deltaTime, deltaTime: deltaTime, relativeTo: nil) { collision in
if collision.hitEntity == collision.characterEntity {
print("hit entity has collided with itself")
}
print("\(collision.characterEntity.name) collided with \(collision.hitEntity.name) ")
}
}
}
}
#Preview(windowStyle: .volumetric) {
ContentView()
}
