Add GroundingShadowComponent to all model entities in a hierarchy

Entity+GenerateGroundingShadowComponents.swift

//
//  Entity+GenerateGroundingShadowComponents.swift
//
//  Created by Drew Olbrich on 10/18/23.
//  Copyright © 2023 Lunar Skydiving LLC. All rights reserved.
//
//  MIT License
//  
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//  
//  The above copyright notice and this permission notice shall be included in all
//  copies or substantial portions of the Software.
//  
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
//  SOFTWARE.
//

import RealityKit

extension Entity {

    /// Assigns a `GroundingShadowComponent` to all `ModelEntity` objects in an entity hierarchy.
    ///
    /// This may create performance problems if more than a dozen grounding shadows are asssigned.
    func generateGroundingShadowComponents() {
        enumerateHierarchy { entity in
            if entity is ModelEntity {
                entity.components.set(GroundingShadowComponent(castsShadow: true))
            }
        }
    }

    private func enumerateHierarchy(_ body: (Entity) -> Void) {
        func enumerate(_ body: (Entity) -> Void) {
            body(self)
            children.forEach { child in
                child.enumerateHierarchy(body)
            }
        }
        enumerate(body)
    }
    
}