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Runtime/MapPlane.cs

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+using UnityEngine;
+
+namespace Jovian.ZoneSystem {
+    /// <summary>
+    ///     Defines which two world axes the map (and zone polygons) lie on.
+    ///     XY = flat sprite / UI map (Z is depth)
+    ///     XZ = 3D world map (Y is up) ← standard Unity 3D
+    ///     YZ = side-on map (X is depth)
+    /// </summary>
+    public enum MapPlane {
+        XY,
+        XZ,
+        YZ
+    }
+
+    public static class MapPlaneUtility {
+        /// <summary>
+        ///     Projects a 3D world position onto the chosen map plane,
+        ///     returning a 2D point suitable for polygon testing.
+        /// </summary>
+        public static Vector2 ProjectToPlane(Vector3 worldPos, MapPlane plane) {
+            switch(plane) {
+                case MapPlane.XY: return new Vector2(worldPos.x, worldPos.y);
+                case MapPlane.XZ: return new Vector2(worldPos.x, worldPos.z);
+                case MapPlane.YZ: return new Vector2(worldPos.y, worldPos.z);
+                default: return new Vector2(worldPos.x, worldPos.y);
+            }
+        }
+
+        /// <summary>
+        ///     Reconstructs a 3D world position from a 2D polygon point on the chosen plane.
+        ///     The depth value fills the axis not covered by the plane.
+        /// </summary>
+        public static Vector3 UnprojectFromPlane(Vector2 point, MapPlane plane, float depth = 0f) {
+            switch(plane) {
+                case MapPlane.XY: return new Vector3(point.x, point.y, depth);
+                case MapPlane.XZ: return new Vector3(point.x, depth, point.y);
+                case MapPlane.YZ: return new Vector3(depth, point.x, point.y);
+                default: return new Vector3(point.x, point.y, depth);
+            }
+        }
+    }
+}