BakeNavMeshForMinimap

using UnityEngine;
using UnityEngine.AI;
using Unity.AI.Navigation;

public class BakeNavMeshForMinimap : MonoBehaviour
{
    [SerializeField] MeshFilter[] filter;
    [SerializeField] GameObject[] roomHolder;
    [SerializeField] NavMeshSurface surface;

    [ContextMenu("Generate Minimap Meshes")]
    void GenerateMinimapMeshes()
    {
        for (int i = 0; i < roomHolder.Length; i++)
        {
            if (roomHolder[i].TryGetComponent(out NavMeshModifier navmeshMod))
            {
                // turn on the component
                navmeshMod.enabled = true;
                surface.BuildNavMesh(); // bake mesh
                filter[i].mesh = BuildMesh(roomHolder[i].transform.position);// offset to the room pos
                navmeshMod.enabled = false;
            }
            else
            {
                Debug.LogWarning("Missing NavMeshModifier component on roomHolder " + i);
            }
        }
    }

    Mesh BuildMesh(Vector3 offset)
    {
        NavMeshData navData = surface.navMeshData;
        // load in navmesh
        NavMeshDataInstance instance = NavMesh.AddNavMeshData(navData);
        // get the data
        NavMeshTriangulation triangulation = NavMesh.CalculateTriangulation();
        Vector3[] offsetVertices = new Vector3[triangulation.vertices.Length];
        // add offset
        for (int i = 0; i < triangulation.vertices.Length; i++)
        {
            offsetVertices[i] = triangulation.vertices[i] - offset;
        }
        // remove navmeshes
        NavMesh.RemoveNavMeshData(instance);
        instance.Remove();
        // create new mesh from data
        Mesh mesh = new Mesh();
        mesh.vertices = offsetVertices;
        mesh.triangles = triangulation.indices;
        return mesh;
    }

}