champions-of-luneraria/Assets/Luneraria/View/LuneSpace.cs

using System;
using Luneraria.Core;
using UnityEngine;

namespace Luneraria.View
{
    /// <summary>
    /// Map and Godot coordinates in Unity. The core works on the map plane (x, y); Godot shows a
    /// map point at (x, height, y) in a right-handed frame. Unity is left-handed, so x flips:
    /// Unity = (-x, height, y). The FBX pipeline uses the same conversion (docs/port/U2-WORLD.md),
    /// so models, world and camera line up, and the picture is Godot's, not its mirror image.
    /// </summary>
    public static class LuneSpace
    {
        public static Vector3 World(Vec2 map, float height)
        {
            return new Vector3(-map.X, height, map.Y);
        }

        public static Vec2 Map(Vector3 world)
        {
            return new Vec2(-world.x, world.z);
        }

        public static Vector3 FromGodot(Vector3 godot)
        {
            return new Vector3(-godot.x, godot.y, godot.z);
        }

        public static Vector3 Direction(Vec2 map)
        {
            return new Vector3(-map.X, 0f, map.Y);
        }

        /// <summary>Rotation that turns a model's front (+Z) towards a map direction.</summary>
        public static Quaternion Facing(Vec2 direction)
        {
            Vector3 v = Direction(direction);
            return v.sqrMagnitude < 1e-12f ? Quaternion.identity : Quaternion.LookRotation(v.normalized, Vector3.up);
        }

        /// <summary>The core's facing angle (atan2(dx, dy), Godot's rotation.y) as a rotation.</summary>
        public static Quaternion Facing(double angle)
        {
            return Facing(new Vec2(Math.Sin(angle), Math.Cos(angle)));
        }

        /// <summary>
        /// A Godot transform (basis columns x, y, z and origin, as written by the world bake) in
        /// Unity: S M S with S = diag(-1, 1, 1). Returns position, rotation and scale; the bake
        /// only contains rotations with positive scale along the basis axes.
        /// </summary>
        public static void FromGodot(float[] t, int offset, out Vector3 position, out Quaternion rotation, out Vector3 scale)
        {
            var x = new Vector3(t[offset + 0], t[offset + 1], t[offset + 2]);
            var y = new Vector3(t[offset + 3], t[offset + 4], t[offset + 5]);
            var z = new Vector3(t[offset + 6], t[offset + 7], t[offset + 8]);
            // Columns of S B S: -(S bx), S by, S bz.
            Vector3 ux = -FromGodot(x);
            Vector3 uy = FromGodot(y);
            Vector3 uz = FromGodot(z);
            scale = new Vector3(ux.magnitude, uy.magnitude, uz.magnitude);
            rotation = Quaternion.LookRotation(uz / Mathf.Max(scale.z, 1e-8f), uy / Mathf.Max(scale.y, 1e-8f));
            position = FromGodot(new Vector3(t[offset + 9], t[offset + 10], t[offset + 11]));
        }
    }
}