meshgen draft

using System;
using System.Collections.Generic;
using UnityEngine;
using Unity.Mathematics;
using Unity.Collections;
using Unity.Jobs;
using Unity.VisualScripting;
using Unity.Burst;
using UnityEngine.Rendering;
using System.Collections;

public class MeshGenerator : MonoBehaviour
{
    public static Vector2Int chunkDimensions = new Vector2Int(32, 128);

    public Material material;
    public ComputeShader voxelGridShader;

    public int brushSize;
    public float brushStrength;

    public int lod;
    public int maxLod;

    public float surfaceLevel;

    public bool hideMeshOnPlay;

    [Header("Noise Settings")]
    public float heightMultiplier;
    public AnimationCurve heightCurve;
    public float frequency;
    public float lacunarity;
    public float persistance;
    public int octaves;
    public float density;
    public float warpingStrength;
    public float warpingFrequency;
    public float mountainHeightOffset;
    public Vector2 offset;

    [Header("")]
    public bool autoUpdate;
    public string executionTime;

    int[] caseToNumpolys;
    int[][] triTable;
    NativeArray<int> nativeTriTable;
    NativeArray<int> nativeCaseToNumPolys;

    Camera cam;

    VoxelGrid voxelGrid;

    private void Start()
    {
        Init();

        if (GameObject.Find("Mesh") != null)
        {
            GameObject.Find("Mesh").SetActive(!hideMeshOnPlay);
        }

    }

    private void Update()
    {
        if (Input.GetKeyDown(KeyCode.Space))
        {
            EditorMesh();
        }
    }

    public GameObject ChunkObject(Vector2 position)
    {
        GameObject chunk = new GameObject("Chunk");
        chunk.AddComponent<MeshFilter>().mesh = ChunkMesh(position, 0);
        chunk.AddComponent<MeshRenderer>().material = material;
        chunk.GetComponent<MeshRenderer>().receiveShadows = false;
        chunk.GetComponent<MeshRenderer>().shadowCastingMode = UnityEngine.Rendering.ShadowCastingMode.Off;

        return chunk;
    }

    public Mesh ChunkMesh(Vector2 position, int lod)
    {
        lod = lod == 0 ? 1 : lod * 2;

        NativeList<float3> nativeVertices = new NativeList<float3>(Allocator.TempJob);
        NativeList<int> nativeIndices = new NativeList<int>(Allocator.TempJob);
        NativeHashMap<float3, int> vertDictionary = new NativeHashMap<float3, int>(256, Allocator.TempJob);
        NativeArray<float> nativeVoxelGrid = voxelGrid.RequestVoxelGrid(position, lod);

        MeshJob job = new MeshJob
        {
            vertices = nativeVertices,
            indices = nativeIndices,
            vertDictionary = vertDictionary,
            voxelGrid = nativeVoxelGrid,
            triTable = nativeTriTable,
            caseToNumPolys = nativeCaseToNumPolys,
            chunkDimensions = new int2(chunkDimensions.x, chunkDimensions.y),
            lod = lod
        };

        job.Schedule().Complete();

        Mesh mesh = new Mesh();
        mesh.indexFormat = UnityEngine.Rendering.IndexFormat.UInt32;

        Vector3[] vertices = new Vector3[nativeVertices.Length];
        int[] indices = new int[nativeIndices.Length];

        for (int i = 0; i < nativeVertices.Length; i++)
        {
            vertices[i] = nativeVertices[i];
        }

        for (int i = 0; i < nativeIndices.Length; i++)
        {
            indices[i] = nativeIndices[i];
        }

        mesh.vertices = vertices;
        mesh.triangles = indices;

        mesh.RecalculateNormals();

        nativeVertices.Dispose();
        nativeIndices.Dispose();
        vertDictionary.Dispose();
        nativeVoxelGrid.Dispose();

        return mesh;
    }

    public void EditorMesh()
    {
        Init();

        float startTime = Time.realtimeSinceStartup;

        Mesh mesh = ChunkMesh(offset / 10, lod);

        executionTime = ((Time.realtimeSinceStartup - startTime) * 1000f) + "ms";

        if (GameObject.Find("Mesh") == null)
        {
            GameObject obj = new GameObject("Mesh");
            obj.transform.parent = transform;
            obj.AddComponent<MeshFilter>().mesh = mesh;
            obj.AddComponent<MeshRenderer>().material = material;
            obj.AddComponent<MeshCollider>();
        }

        else
        {
            var mf = GameObject.Find("Mesh").GetComponent<MeshFilter>();
            var collider = GameObject.Find("Mesh").GetComponent<MeshCollider>();

            mf.mesh = mesh;
            collider.sharedMesh = null;
            collider.sharedMesh = mesh;
        }
    }

    void Init()
    {
        caseToNumpolys = Tables.caseToNumPolys;
        triTable = Tables.triTable;

        nativeTriTable = new NativeArray<int>(256 * 15, Allocator.Persistent);
        nativeCaseToNumPolys = new NativeArray<int>(256, Allocator.Persistent);


        for (int i = 0; i < triTable.Length; i++)
        {
            nativeCaseToNumPolys[i] = caseToNumpolys[i];

            for (int j = 0; j < 15; j++)
            {
                nativeTriTable[(i * 15) + j] = triTable[i][j];
            }
        }

        cam = Camera.main;

        voxelGrid = new VoxelGrid(frequency, lacunarity, persistance, octaves, surfaceLevel, density, heightMultiplier, voxelGridShader);
    }

    IEnumerator ReadVoxelGrid(int length, ComputeBuffer buffer)
    {
        voxelGridShader.Dispatch(0, length, 1, 1);

        AsyncGPUReadbackRequest request = AsyncGPUReadback.Request(buffer);

        while (!request.done)
        {
            yield return null;
        }

        if (request.hasError)
        {
            Debug.LogWarning("GPU readback error detected.");
        }
        else
        {
            ConstructMesh(request.GetData<float>().ToArray());
        }
    }

    void ConstructMesh(float[] voxelGrid)
    {

    }
}

[BurstCompile]
struct MeshJob : IJob
{
    public NativeList<float3> vertices;
    public NativeList<int> indices;
    public NativeHashMap<float3, int> vertDictionary;

    [ReadOnly] public NativeArray<float> voxelGrid;
    [ReadOnly] public NativeArray<int> triTable;
    [ReadOnly] public NativeArray<int> caseToNumPolys;
    [ReadOnly] public int2 chunkDimensions;
    [ReadOnly] public int lod;

    public void Execute()
    {
        for (int z = 0, i = 0; z < chunkDimensions.x; z += lod)
        {
            for (int y = 0; y < chunkDimensions.y; y += lod)
            {
                for (int x = 0; x < chunkDimensions.x; x += lod, i++)
                {
                    AddVertices(i, x, y, z);
                }
            }
        }
    }

    void AddVertices(int index, int x, int y, int z)
    {
        int triCase = CalculateCase(index);

        for (int j = 0, i = 0; j < caseToNumPolys[triCase]; j++, i += 3)
        {
            for (int h = 0; h < 3; h++)
            {
                int edge = triTable[(triCase * 15) + i + (2 - h)];
                float3 vertex = GetEdgePosition(edge, index, lod, x, y, z);

                if (vertDictionary.ContainsKey(vertex))
                {
                    indices.Add(vertDictionary[vertex]);
                }

                else
                {
                    vertices.Add(vertex);
                    indices.Add(vertices.Length - 1);

                    vertDictionary.Add(vertex, vertices.Length - 1);
                }
            }
        }
    }

    float3 GetEdgePosition(int edge, int index, int lod, int x, int y, int z)
    {
        int i = index * 8;

        switch (edge)
        {
            case 0: return GetInterpolatedEdgePosition(x, y, z, voxelGrid[i], voxelGrid[i + 1], 0, 1, 0);
            case 1: return GetInterpolatedEdgePosition(x, y + lod, z, voxelGrid[i + 1], voxelGrid[i + 2], 1, 0, 0);
            case 2: return GetInterpolatedEdgePosition(x + lod, y, z, voxelGrid[i + 3], voxelGrid[i + 2], 0, 1, 0);
            case 3: return GetInterpolatedEdgePosition(x, y, z, voxelGrid[i], voxelGrid[i + 3], 1, 0, 0);

            case 4: return GetInterpolatedEdgePosition(x, y, z + lod, voxelGrid[i + 4], voxelGrid[i + 5], 0, 1, 0);
            case 5: return GetInterpolatedEdgePosition(x, y + lod, z + lod, voxelGrid[i + 5], voxelGrid[i + 6], 1, 0, 0);
            case 6: return GetInterpolatedEdgePosition(x + lod, y, z + lod, voxelGrid[i + 7], voxelGrid[i + 6], 0, 1, 0);
            case 7: return GetInterpolatedEdgePosition(x, y, z + lod, voxelGrid[i + 4], voxelGrid[i + 7], 1, 0, 0);

            case 8: return GetInterpolatedEdgePosition(x, y, z, voxelGrid[i], voxelGrid[i + 4], 0, 0, 1);
            case 9: return GetInterpolatedEdgePosition(x, y + lod, z, voxelGrid[i + 1], voxelGrid[i + 5], 0, 0, 1);
            case 10: return GetInterpolatedEdgePosition(x + lod, y + lod, z, voxelGrid[i + 2], voxelGrid[i + 6], 0, 0, 1);
            case 11: return GetInterpolatedEdgePosition(x + lod, y, z, voxelGrid[i + 3], voxelGrid[i + 7], 0, 0, 1);

            default: throw new ArgumentOutOfRangeException(nameof(edge), "Invalid edge index: " + edge);
        }
    }
    public float3 GetInterpolatedEdgePosition(int x, int y, int z, float voxelA, float voxelB, int offsetX, int offsetY, int offsetZ)
    {
        float interpolation = (0 - voxelA) / (voxelB - voxelA);

        return new float3(x + offsetX * interpolation, y + offsetY * interpolation, z + offsetZ * interpolation);
    }

    public int CalculateCase(int index)
    {
        int triCase = 0;

        for (int i = 0; i < 8; i++)
        {
            int bit = voxelGrid[(index * 8) + i] < 0 ? 1 : 0;
            triCase |= bit << i;
        }

        return triCase;
    }
}