Initial commit for first version of project

GasTankAR/Views/TankAR/DirtTextureFactory.swift

@@ -0,0 +1,57 @@
+//
+//  DirtTextureFactory.swift
+//  GasTankAR
+//
+//  Created by Dennis Nemec on 28.08.26.
+//
+
+import RealityKit
+import UIKit
+
+/// Erzeugt prozedural eine kachelbare Erd-/Dreck-Textur (ohne Bild-Asset) für die Grubenwand,
+/// damit sichtbar wird, dass sich der Tank unter der Erde befindet.
+@MainActor
+enum DirtTextureFactory {
+    /// Einmalig erzeugte, wiederverwendete Textur.
+    static let texture: TextureResource? = makeTexture()
+
+    private static func makeTexture() -> TextureResource? {
+        let size = CGSize(width: 256, height: 256)
+        let image = UIGraphicsImageRenderer(size: size).image { context in
+            let rect = CGRect(origin: .zero, size: size)
+
+            // Erd-Grundton.
+            UIColor(red: 0.42, green: 0.30, blue: 0.18, alpha: 1).setFill()
+            context.fill(rect)
+
+            // Größere Erdflecken / Steine für Struktur.
+            for _ in 0..<70 {
+                let diameter = CGFloat.random(in: 6...26)
+                let origin = CGPoint(x: .random(in: -10...size.width), y: .random(in: -10...size.height))
+                let brightness = CGFloat.random(in: -0.12...0.12)
+                UIColor(
+                    red: max(0, min(1, 0.42 + brightness)),
+                    green: max(0, min(1, 0.30 + brightness)),
+                    blue: max(0, min(1, 0.18 + brightness)),
+                    alpha: 1
+                ).setFill()
+                context.cgContext.fillEllipse(in: CGRect(x: origin.x, y: origin.y, width: diameter, height: diameter))
+            }
+
+            // Feine Körnung (helle + dunkle Sprenkel).
+            for _ in 0..<2000 {
+                let point = CGPoint(x: .random(in: 0..<size.width), y: .random(in: 0..<size.height))
+                let diameter = CGFloat.random(in: 0.5...2.5)
+                let isDark = Bool.random()
+                let color = isDark
+                    ? UIColor(white: 0, alpha: .random(in: 0.05...0.2))
+                    : UIColor(white: 1, alpha: .random(in: 0.03...0.12))
+                color.setFill()
+                context.cgContext.fillEllipse(in: CGRect(x: point.x, y: point.y, width: diameter, height: diameter))
+            }
+        }
+
+        guard let cgImage = image.cgImage else { return nil }
+        return try? TextureResource.generate(from: cgImage, options: .init(semantic: .color))
+    }
+}