RealityKit Soft Shadows & Physical Space Lighting

import RealityKit
import SwiftUI

struct PlanetariumView: View {
    var body: some View {
        RealityView { content in
            let projectorEntity = makePlanetariumSpotlight()
            content.add(projectorEntity)

            let cauldron = makeCauldronScene()
            content.add(cauldron)
        }
    }
}

// MARK: - Soft Shadow Spotlight (hearth example)
func makeHearthSpotlight() -> Entity {
    let entity = Entity()

    var spotlight = SpotLightComponent(
        color: .init(red: 1.0, green: 0.6, blue: 0.2, alpha: 1.0),
        intensity: 8000,
        innerAngleInDegrees: 20,
        outerAngleInDegrees: 45,
        attenuationRadius: 5.0
    )

    // Configure soft shadow — lightSize is diameter in meters
    var shadow = SpotLightComponent.Shadow()
    shadow.lightSize = 0.7          // 0 = hard shadow (default)
    shadow.quality = .medium        // .low ignores lightSize and stays hard
    spotlight.shadow = shadow

    entity.components.set(spotlight)
    entity.position = [0, 1.5, -1]
    return entity
}

// MARK: - Projective Texture + Physical Space Lighting
func makePlanetariumSpotlight() -> Entity {
    let entity = Entity()

    // White spotlight so projective texture colors show through unmodified
    var spotlight = SpotLightComponent(
        color: .white,
        intensity: 12000,
        innerAngleInDegrees: 30,
        outerAngleInDegrees: 60,
        attenuationRadius: 8.0
    )
    entity.components.set(spotlight)

    // Load or generate a star-field texture
    if let starTexture = try? TextureResource.load(named: "stars_nebulae") {
        let projective = ProjectiveTextureComponent(texture: starTexture)
        entity.components.set(projective)
    }

    // Enable physical space lighting — casts onto real-world surfaces
    // Only needs to be added; no configuration required
    entity.components.set(SpotLightComponent.SurroundingsLightComponent())

    entity.position = [0, 1.8, 0]
    return entity
}

// MARK: - Placeholder scene entity
func makeCauldronScene() -> Entity {
    let entity = Entity()
    // In a real project load a USD: try? Entity.load(named: "cauldron")
    entity.position = [0, 0, -1.5]
    return entity
}