Geometry

using System.Collections.Generic;
using System.Linq;
using UnityEngine;

internal class Geometry
{
    private readonly List<Vector3> _vertices;
    private readonly List<Vector3> _normals;
    private readonly List<Color> _colors;
    private readonly List<Vector2> _uvs;
    private readonly List<int> _triangles;

    public Geometry()
    {
        _vertices = new List<Vector3>();
        _normals = new List<Vector3>();
        _colors = new List<Color>();
        _uvs = new List<Vector2>();
        _triangles = new List<int>();
    }

    public Geometry(Mesh unityMesh)
    {
        _vertices = new List<Vector3>(unityMesh.vertices);
        _normals = new List<Vector3>(unityMesh.normals);
        _colors = new List<Color>(unityMesh.colors);
        _uvs = new List<Vector2>(unityMesh.uv);
        _triangles = new List<int>(unityMesh.triangles);
    }

    public bool IsEmpty()
    {
        return _vertices.Count == 0;
    }

    public void Clear()
    {
        _vertices.Clear();
        _normals.Clear();
        _colors.Clear();
        _uvs.Clear();
        _triangles.Clear();
    }

    public static Mesh ConvertToUnityMeshWithSubmeshes(List<Geometry> geometries)
    {
        var vertices = new List<Vector3>();
        var uvs = new List<Vector2>();
        var normals = new List<Vector3>();
        var colors = new List<Color>();
        var tangents = new List<Vector4>();

        foreach (var geometry in geometries)
        {
            vertices.AddRange(geometry._vertices);
            uvs.AddRange(geometry._uvs);
            normals.AddRange(geometry._normals);
            colors.AddRange(geometry._colors);
            tangents.AddRange(geometry.CalculateTangents());
        }

        var mesh = new Mesh
                    {
                        vertices = vertices.ToArray(),
                        uv = uvs.ToArray(),
                        normals = normals.ToArray(),
                        colors = colors.ToArray(),
                        tangents = tangents.ToArray(),
                        subMeshCount = geometries.Count,
                    };

        int vertexShift = 0;
        for (int submeshIndex = 0; submeshIndex < geometries.Count; submeshIndex++)
        {
            var geometry = geometries[submeshIndex];

            var triangles = geometry._triangles.Select(t => t + vertexShift).ToArray();
            mesh.SetTriangles(triangles, submeshIndex);

            vertexShift += geometry._vertices.Count;
        }

        return mesh;
    }

    public Mesh ConvertToUnityMesh()
    {
        var mesh = new Mesh
                    {
                        vertices = _vertices.ToArray(),
                        triangles = _triangles.ToArray()
                    };

        if (_uvs != null)
        {
            mesh.normals = _normals.ToArray();
            mesh.uv = _uvs.ToArray();
            mesh.colors = _colors.ToArray();
            if (_uvs.Count == _vertices.Count)
            {
                mesh.tangents = CalculateTangents();
            }
        }

        return mesh;
    }

    public void AppendFace(FaceDirection direction, float x, float y, float z, LightColor c1, LightColor c2, LightColor c3, LightColor c4, float u, float v)
    {
        switch (direction)
        {
            case FaceDirection.Up:
                AppendUpFace(x, y + 1, z, 1, 1, c1, c2, c3, c4, u, v);
                break;
            case FaceDirection.Down:
                AppendDownFace(x, y, z, 1, 1, c1, c2, c3, c4, u, v);
                break;
            case FaceDirection.North:
                AppendNorthFace(x, y, z + 1, 1, 1, c1, c2, c3, c4, u, v);
                break;
            case FaceDirection.South:
                AppendSouthFace(x, y, z, 1, 1, c1, c2, c3, c4, u, v);
                break;
            case FaceDirection.East:
                AppendEastFace(x + 1, y, z, 1, 1, c1, c2, c3, c4, u, v);
                break;
            case FaceDirection.West:
                AppendWestFace(x, y, z, 1, 1, c1, c2, c3, c4, u, v);
                break;
        }
    }

    public int AppendGeometry(Vector3 position, Geometry geometry)
    {
        return AppendGeometry(position, geometry._vertices, geometry._normals, geometry._uvs, geometry._colors, geometry._triangles);
    }

    /// <param name = "textureShift">Must be between 0 and 0.5</param>
    public void AppendGrassBillboard1(float x, float y, float z, float height, float textureShift, LightColor c1, LightColor c2, LightColor c3, LightColor c4)
    {
        var v1 = _vertices.Count;
        _vertices.Add(new Vector3(x + 0, y + 0, z + 0));
        _vertices.Add(new Vector3(x + 1, y + 0, z + 1));
        _vertices.Add(new Vector3(x + 1, y + height, z + 1));
        _vertices.Add(new Vector3(x + 0, y + height, z + 0));
        var v2 = _vertices.Count;
        _vertices.Add(new Vector3(x + 0, y + 0, z + 1));
        _vertices.Add(new Vector3(x + 1, y + 0, z + 0));
        _vertices.Add(new Vector3(x + 1, y + height, z + 0));
        _vertices.Add(new Vector3(x + 0, y + height, z + 1));

        _colors.Add((Color)c1);
        _colors.Add((Color)c3);
        _colors.Add((Color)c3);
        _colors.Add((Color)c1);
        _colors.Add((Color)c4);
        _colors.Add((Color)c2);
        _colors.Add((Color)c2);
        _colors.Add((Color)c4);

        _normals.Add(new Vector3(-0.70716f, 0, 0.70716f));
        _normals.Add(new Vector3(-0.70716f, 0, 0.70716f));
        _normals.Add(new Vector3(-0.70716f, 0, 0.70716f));
        _normals.Add(new Vector3(-0.70716f, 0, 0.70716f));
        _normals.Add(new Vector3(0.70716f, 0, 0.70716f));
        _normals.Add(new Vector3(0.70716f, 0, 0.70716f));
        _normals.Add(new Vector3(0.70716f, 0, 0.70716f));
        _normals.Add(new Vector3(0.70716f, 0, 0.70716f));

        _uvs.Add(new Vector2(0 + textureShift, 0));
        _uvs.Add(new Vector2(1 + textureShift, 0));
        _uvs.Add(new Vector2(1 + textureShift, 1));
        _uvs.Add(new Vector2(0 + textureShift, 1));
        _uvs.Add(new Vector2(0 + textureShift, 0));
        _uvs.Add(new Vector2(1 + textureShift, 0));
        _uvs.Add(new Vector2(1 + textureShift, 1));
        _uvs.Add(new Vector2(0 + textureShift, 1));

        _triangles.Add(v1 + 0);
        _triangles.Add(v1 + 3);
        _triangles.Add(v1 + 2);
        _triangles.Add(v1 + 2);
        _triangles.Add(v1 + 1);
        _triangles.Add(v1 + 0);
        _triangles.Add(v2 + 0);
        _triangles.Add(v2 + 3);
        _triangles.Add(v2 + 2);
        _triangles.Add(v2 + 2);
        _triangles.Add(v2 + 1);
        _triangles.Add(v2 + 0);
    }

    /// <param name = "textureShift">Must be between 0 and 0.5</param>
    public void AppendGrassBillboard1ReversedTexture(float x, float y, float z, float height, float textureShift, LightColor c1, LightColor c2, LightColor c3, LightColor c4)
    {
        var v1 = _vertices.Count;
        _vertices.Add(new Vector3(x + 0, y + 0, z + 0));
        _vertices.Add(new Vector3(x + 1, y + 0, z + 1));
        _vertices.Add(new Vector3(x + 1, y + height, z + 1));
        _vertices.Add(new Vector3(x + 0, y + height, z + 0));
        var v2 = _vertices.Count;
        _vertices.Add(new Vector3(x + 0, y + 0, z + 1));
        _vertices.Add(new Vector3(x + 1, y + 0, z + 0));
        _vertices.Add(new Vector3(x + 1, y + height, z + 0));
        _vertices.Add(new Vector3(x + 0, y + height, z + 1));

        _colors.Add((Color)c1);
        _colors.Add((Color)c3);
        _colors.Add((Color)c3);
        _colors.Add((Color)c1);
        _colors.Add((Color)c4);
        _colors.Add((Color)c2);
        _colors.Add((Color)c2);
        _colors.Add((Color)c4);

        _normals.Add(new Vector3(-0.70716f, 0, 0.70716f));
        _normals.Add(new Vector3(-0.70716f, 0, 0.70716f));
        _normals.Add(new Vector3(-0.70716f, 0, 0.70716f));
        _normals.Add(new Vector3(-0.70716f, 0, 0.70716f));
        _normals.Add(new Vector3(0.70716f, 0, 0.70716f));
        _normals.Add(new Vector3(0.70716f, 0, 0.70716f));
        _normals.Add(new Vector3(0.70716f, 0, 0.70716f));
        _normals.Add(new Vector3(0.70716f, 0, 0.70716f));

        _uvs.Add(new Vector2(1 + textureShift, 0));
        _uvs.Add(new Vector2(0 + textureShift, 0));
        _uvs.Add(new Vector2(0 + textureShift, 1));
        _uvs.Add(new Vector2(1 + textureShift, 1));
        _uvs.Add(new Vector2(1 + textureShift, 0));
        _uvs.Add(new Vector2(0 + textureShift, 0));
        _uvs.Add(new Vector2(0 + textureShift, 1));
        _uvs.Add(new Vector2(1 + textureShift, 1));

        _triangles.Add(v1 + 0);
        _triangles.Add(v1 + 3);
        _triangles.Add(v1 + 2);
        _triangles.Add(v1 + 2);
        _triangles.Add(v1 + 1);
        _triangles.Add(v1 + 0);
        _triangles.Add(v2 + 0);
        _triangles.Add(v2 + 3);
        _triangles.Add(v2 + 2);
        _triangles.Add(v2 + 2);
        _triangles.Add(v2 + 1);
        _triangles.Add(v2 + 0);
    }

    /// <param name = "textureShift">Must be between 0 and 0.5</param>
    public void AppendGrassBillboard2(float x, float y, float z, float height, float textureShift, LightColor color)
    {
        var v1 = _vertices.Count;
        _vertices.Add(new Vector3(x + 0, y + 0, z + .5f));
        _vertices.Add(new Vector3(x + 1, y + 0, z + .5f));
        _vertices.Add(new Vector3(x + 1, y + height, z + .5f));
        _vertices.Add(new Vector3(x + 0, y + height, z + .5f));
        var v2 = _vertices.Count;
        _vertices.Add(new Vector3(x + .5f, y + 0, z + 1));
        _vertices.Add(new Vector3(x + .5f, y + 0, z + 0));
        _vertices.Add(new Vector3(x + .5f, y + height, z + 0));
        _vertices.Add(new Vector3(x + .5f, y + height, z + 1));

        _colors.Add((Color)color);
        _colors.Add((Color)color);
        _colors.Add((Color)color);
        _colors.Add((Color)color);
        _colors.Add((Color)color);
        _colors.Add((Color)color);
        _colors.Add((Color)color);
        _colors.Add((Color)color);

        _normals.Add(Vector3.forward);
        _normals.Add(Vector3.forward);
        _normals.Add(Vector3.forward);
        _normals.Add(Vector3.forward);
        _normals.Add(Vector3.right);
        _normals.Add(Vector3.right);
        _normals.Add(Vector3.right);
        _normals.Add(Vector3.right);

        _uvs.Add(new Vector2(0 + textureShift, 0));
        _uvs.Add(new Vector2(1 + textureShift, 0));
        _uvs.Add(new Vector2(1 + textureShift, 1));
        _uvs.Add(new Vector2(0 + textureShift, 1));
        _uvs.Add(new Vector2(0 + textureShift, 0));
        _uvs.Add(new Vector2(1 + textureShift, 0));
        _uvs.Add(new Vector2(1 + textureShift, 1));
        _uvs.Add(new Vector2(0 + textureShift, 1));

        _triangles.Add(v1 + 0);
        _triangles.Add(v1 + 3);
        _triangles.Add(v1 + 2);
        _triangles.Add(v1 + 2);
        _triangles.Add(v1 + 1);
        _triangles.Add(v1 + 0);
        _triangles.Add(v2 + 0);
        _triangles.Add(v2 + 3);
        _triangles.Add(v2 + 2);
        _triangles.Add(v2 + 2);
        _triangles.Add(v2 + 1);
        _triangles.Add(v2 + 0);
    }

    /// <param name = "textureShift">Must be between 0 and 0.5</param>
    public void AppendGrassBillboard2ReversedTexture(float x, float y, float z, float height, float textureShift, LightColor color)
    {
        var v1 = _vertices.Count;
        _vertices.Add(new Vector3(x + 0, y + 0, z + .5f));
        _vertices.Add(new Vector3(x + 1, y + 0, z + .5f));
        _vertices.Add(new Vector3(x + 1, y + height, z + .5f));
        _vertices.Add(new Vector3(x + 0, y + height, z + .5f));
        var v2 = _vertices.Count;
        _vertices.Add(new Vector3(x + .5f, y + 0, z + 1));
        _vertices.Add(new Vector3(x + .5f, y + 0, z + 0));
        _vertices.Add(new Vector3(x + .5f, y + height, z + 0));
        _vertices.Add(new Vector3(x + .5f, y + height, z + 1));

        _colors.Add((Color)color);
        _colors.Add((Color)color);
        _colors.Add((Color)color);
        _colors.Add((Color)color);
        _colors.Add((Color)color);
        _colors.Add((Color)color);
        _colors.Add((Color)color);
        _colors.Add((Color)color);

        _normals.Add(Vector3.forward);
        _normals.Add(Vector3.forward);
        _normals.Add(Vector3.forward);
        _normals.Add(Vector3.forward);
        _normals.Add(Vector3.right);
        _normals.Add(Vector3.right);
        _normals.Add(Vector3.right);
        _normals.Add(Vector3.right);

        _uvs.Add(new Vector2(1 + textureShift, 0));
        _uvs.Add(new Vector2(0 + textureShift, 0));
        _uvs.Add(new Vector2(0 + textureShift, 1));
        _uvs.Add(new Vector2(1 + textureShift, 1));
        _uvs.Add(new Vector2(1 + textureShift, 0));
        _uvs.Add(new Vector2(0 + textureShift, 0));
        _uvs.Add(new Vector2(0 + textureShift, 1));
        _uvs.Add(new Vector2(1 + textureShift, 1));

        _triangles.Add(v1 + 0);
        _triangles.Add(v1 + 3);
        _triangles.Add(v1 + 2);
        _triangles.Add(v1 + 2);
        _triangles.Add(v1 + 1);
        _triangles.Add(v1 + 0);
        _triangles.Add(v2 + 0);
        _triangles.Add(v2 + 3);
        _triangles.Add(v2 + 2);
        _triangles.Add(v2 + 2);
        _triangles.Add(v2 + 1);
        _triangles.Add(v2 + 0);
    }

    #region Upper faces
    public void AppendUpFace(float x, float y, float z, int xSize, int zSize, LightColor cSW, LightColor cSE, LightColor cNE, LightColor cNW, float wx, float wz)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, y, z));
        _vertices.Add(new Vector3(x + xSize, y, z));
        _vertices.Add(new Vector3(x + xSize, y, z + zSize));
        _vertices.Add(new Vector3(x, y, z + zSize));

        _colors.Add((Color)cSW);
        _colors.Add((Color)cSE);
        _colors.Add((Color)cNE);
        _colors.Add((Color)cNW);

        _normals.Add(Vector3.up);
        _normals.Add(Vector3.up);
        _normals.Add(Vector3.up);
        _normals.Add(Vector3.up);

        _uvs.Add(new Vector2(Low(wx), Low(wz)));
        _uvs.Add(new Vector2(High(wx + xSize), Low(wz)));
        _uvs.Add(new Vector2(High(wx + xSize), High(wz + zSize)));
        _uvs.Add(new Vector2(Low(wx), High(wz + zSize)));

        _triangles.Add(v + 0);
        _triangles.Add(v + 3);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 1);
        _triangles.Add(v + 0);
    }

    public void AppendUpFaceWater(float x, float z, float ySW, float ySE, float yNE, float yNW, LightColor cSW, LightColor cSE, LightColor cNE, LightColor cNW, float wx, float wz)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, ySW, z));
        _vertices.Add(new Vector3(x + 1, ySE, z));
        _vertices.Add(new Vector3(x + 1, yNE, z + 1));
        _vertices.Add(new Vector3(x, yNW, z + 1));

        _colors.Add((Color)cSW);
        _colors.Add((Color)cSE);
        _colors.Add((Color)cNE);
        _colors.Add((Color)cNW);

        _normals.Add(Vector3.up);
        _normals.Add(Vector3.up);
        _normals.Add(Vector3.up);
        _normals.Add(Vector3.up);

        _uvs.Add(new Vector2(Low(wx), Low(wz)));
        _uvs.Add(new Vector2(High(wx + 1), Low(wz)));
        _uvs.Add(new Vector2(High(wx + 1), High(wz + 1)));
        _uvs.Add(new Vector2(Low(wx), High(wz + 1)));

        _triangles.Add(v + 0);
        _triangles.Add(v + 3);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 1);
        _triangles.Add(v + 0);
    }

    public void AppendUpFaceCollider(float x, float y, float z, int xSize, int zSize)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, y, z));
        _vertices.Add(new Vector3(x + xSize, y, z));
        _vertices.Add(new Vector3(x + xSize, y, z + zSize));
        _vertices.Add(new Vector3(x, y, z + zSize));

        _triangles.Add(v + 0);
        _triangles.Add(v + 3);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 1);
        _triangles.Add(v + 0);
    }
    #endregion

    #region Lower faces
    public void AppendDownFace(float x, float y, float z, int xSize, int zSize, LightColor cSW, LightColor cSE, LightColor cNE, LightColor cNW, float wx, float wz)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, y, z));
        _vertices.Add(new Vector3(x + xSize, y, z));
        _vertices.Add(new Vector3(x + xSize, y, z + zSize));
        _vertices.Add(new Vector3(x, y, z + zSize));

        _colors.Add((Color)cSW);
        _colors.Add((Color)cSE);
        _colors.Add((Color)cNE);
        _colors.Add((Color)cNW);

        _normals.Add(Vector3.up);
        _normals.Add(Vector3.up);
        _normals.Add(Vector3.up);
        _normals.Add(Vector3.up);

        _uvs.Add(new Vector2(Low(wx), High(wz)));
        _uvs.Add(new Vector2(High(wx + xSize), High(wz)));
        _uvs.Add(new Vector2(High(wx + xSize), Low(wz - zSize)));
        _uvs.Add(new Vector2(Low(wx), Low(wz - zSize)));

        _triangles.Add(v + 0);
        _triangles.Add(v + 1);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 3);
        _triangles.Add(v + 0);
    }

    public void AppendDownFaceWater(float x, float y, float z, LightColor cSW, LightColor cSE, LightColor cNE, LightColor cNW, float wx, float wz)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, y, z));
        _vertices.Add(new Vector3(x + 1, y, z));
        _vertices.Add(new Vector3(x + 1, y, z + 1));
        _vertices.Add(new Vector3(x, y, z + 1));

        _colors.Add((Color)cSW);
        _colors.Add((Color)cSE);
        _colors.Add((Color)cNE);
        _colors.Add((Color)cNW);

        _normals.Add(Vector3.up);
        _normals.Add(Vector3.up);
        _normals.Add(Vector3.up);
        _normals.Add(Vector3.up);

        _uvs.Add(new Vector2(Low(wx), High(wz)));
        _uvs.Add(new Vector2(High(wx + 1), High(wz)));
        _uvs.Add(new Vector2(High(wx + 1), Low(wz - 1)));
        _uvs.Add(new Vector2(Low(wx), Low(wz - 1)));

        _triangles.Add(v + 0);
        _triangles.Add(v + 1);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 3);
        _triangles.Add(v + 0);
    }

    public void AppendDownFaceCollider(float x, float y, float z, int xSize, int zSize)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, y, z));
        _vertices.Add(new Vector3(x + xSize, y, z));
        _vertices.Add(new Vector3(x + xSize, y, z + zSize));
        _vertices.Add(new Vector3(x, y, z + zSize));

        _triangles.Add(v + 0);
        _triangles.Add(v + 1);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 3);
        _triangles.Add(v + 0);
    }
    #endregion

    #region Northern faces
    public void AppendNorthFace(float x, float y, float z, int xSize, int ySize, LightColor cWD, LightColor cED, LightColor cEU, LightColor cWU, float wx, float wy)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, y, z));
        _vertices.Add(new Vector3(x + xSize, y, z));
        _vertices.Add(new Vector3(x + xSize, y + ySize, z));
        _vertices.Add(new Vector3(x, y + ySize, z));

        _colors.Add((Color)cWD);
        _colors.Add((Color)cED);
        _colors.Add((Color)cEU);
        _colors.Add((Color)cWU);

        _normals.Add(Vector3.forward);
        _normals.Add(Vector3.forward);
        _normals.Add(Vector3.forward);
        _normals.Add(Vector3.forward);

        _uvs.Add(new Vector2(High(-wx), Low(wy)));
        _uvs.Add(new Vector2(Low(-wx - xSize), Low(wy)));
        _uvs.Add(new Vector2(Low(-wx - xSize), High(wy + ySize)));
        _uvs.Add(new Vector2(High(-wx), High(wy + ySize)));

        _triangles.Add(v + 0);
        _triangles.Add(v + 1);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 3);
        _triangles.Add(v + 0);
    }

    public void AppendNorthFaceWater(float x, float z, float yD, float yUW, float yUE, LightColor cWD, LightColor cED, LightColor cEU, LightColor cWU, float wx, float wy)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, yD, z));
        _vertices.Add(new Vector3(x + 1, yD, z));
        _vertices.Add(new Vector3(x + 1, yUE, z));
        _vertices.Add(new Vector3(x, yUW, z));

        _colors.Add((Color)cWD);
        _colors.Add((Color)cED);
        _colors.Add((Color)cEU);
        _colors.Add((Color)cWU);

        _normals.Add(Vector3.forward);
        _normals.Add(Vector3.forward);
        _normals.Add(Vector3.forward);
        _normals.Add(Vector3.forward);

        _uvs.Add(new Vector2(High(-wx), Low(wy)));
        _uvs.Add(new Vector2(Low(-wx - 1), Low(wy)));
        _uvs.Add(new Vector2(Low(-wx - 1), High(wy + 1)));
        _uvs.Add(new Vector2(High(-wx), High(wy + 1)));

        _triangles.Add(v + 0);
        _triangles.Add(v + 1);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 3);
        _triangles.Add(v + 0);
    }

    public void AppendNorthFaceCollider(float x, float y, float z, int xSize, int ySize)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, y, z));
        _vertices.Add(new Vector3(x + xSize, y, z));
        _vertices.Add(new Vector3(x + xSize, y + ySize, z));
        _vertices.Add(new Vector3(x, y + ySize, z));

        _triangles.Add(v + 0);
        _triangles.Add(v + 1);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 3);
        _triangles.Add(v + 0);
    }
    #endregion

    #region Southern faces
    public void AppendSouthFace(float x, float y, float z, int xSize, int ySize, LightColor cWD, LightColor cED, LightColor cEU, LightColor cWU, float wx, float wy)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, y, z));
        _vertices.Add(new Vector3(x + xSize, y, z));
        _vertices.Add(new Vector3(x + xSize, y + ySize, z));
        _vertices.Add(new Vector3(x, y + ySize, z));

        _colors.Add((Color)cWD);
        _colors.Add((Color)cED);
        _colors.Add((Color)cEU);
        _colors.Add((Color)cWU);

        _normals.Add(Vector3.back);
        _normals.Add(Vector3.back);
        _normals.Add(Vector3.back);
        _normals.Add(Vector3.back);

        _uvs.Add(new Vector2(Low(wx), Low(wy)));
        _uvs.Add(new Vector2(High(wx + xSize), Low(wy)));
        _uvs.Add(new Vector2(High(wx + xSize), High(wy + ySize)));
        _uvs.Add(new Vector2(Low(wx), High(wy + ySize)));

        _triangles.Add(v + 0);
        _triangles.Add(v + 3);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 1);
        _triangles.Add(v + 0);
    }

    public void AppendSouthFaceWater(float x, float z, float yD, float yUW, float yUE, LightColor cWD, LightColor cED, LightColor cEU, LightColor cWU, float wx, float wy)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, yD, z));
        _vertices.Add(new Vector3(x + 1, yD, z));
        _vertices.Add(new Vector3(x + 1, yUE, z));
        _vertices.Add(new Vector3(x, yUW, z));

        _colors.Add((Color)cWD);
        _colors.Add((Color)cED);
        _colors.Add((Color)cEU);
        _colors.Add((Color)cWU);

        _normals.Add(Vector3.back);
        _normals.Add(Vector3.back);
        _normals.Add(Vector3.back);
        _normals.Add(Vector3.back);

        _uvs.Add(new Vector2(Low(wx), Low(wy)));
        _uvs.Add(new Vector2(High(wx + 1), Low(wy)));
        _uvs.Add(new Vector2(High(wx + 1), High(wy + 1)));
        _uvs.Add(new Vector2(Low(wx), High(wy + 1)));

        _triangles.Add(v + 0);
        _triangles.Add(v + 3);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 1);
        _triangles.Add(v + 0);
    }

    public void AppendSouthFaceCollider(float x, float y, float z, int xSize, int ySize)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, y, z));
        _vertices.Add(new Vector3(x + xSize, y, z));
        _vertices.Add(new Vector3(x + xSize, y + ySize, z));
        _vertices.Add(new Vector3(x, y + ySize, z));

        _triangles.Add(v + 0);
        _triangles.Add(v + 3);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 1);
        _triangles.Add(v + 0);
    }
    #endregion

    #region Western faces
    public void AppendWestFace(float x, float y, float z, int ySize, int zSize, LightColor cSD, LightColor cND, LightColor cNU, LightColor cSU, float wy, float wz)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, y, z));
        _vertices.Add(new Vector3(x, y, z + zSize));
        _vertices.Add(new Vector3(x, y + ySize, z + zSize));
        _vertices.Add(new Vector3(x, y + ySize, z));

        _colors.Add((Color)cSD);
        _colors.Add((Color)cND);
        _colors.Add((Color)cNU);
        _colors.Add((Color)cSU);

        _normals.Add(Vector3.left);
        _normals.Add(Vector3.left);
        _normals.Add(Vector3.left);
        _normals.Add(Vector3.left);

        _uvs.Add(new Vector2(High(-wz + zSize), Low(wy)));
        _uvs.Add(new Vector2(Low(-wz), Low(wy)));
        _uvs.Add(new Vector2(Low(-wz), High(wy + ySize)));
        _uvs.Add(new Vector2(High(-wz + zSize), High(wy + ySize)));

        _triangles.Add(v + 0);
        _triangles.Add(v + 1);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 3);
        _triangles.Add(v + 0);
    }

    public void AppendWestFaceWater(float x, float z, float yD, float yUS, float yUN, LightColor cSD, LightColor cND, LightColor cNU, LightColor cSU, float wy, float wz)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, yD, z));
        _vertices.Add(new Vector3(x, yD, z + 1));
        _vertices.Add(new Vector3(x, yUN, z + 1));
        _vertices.Add(new Vector3(x, yUS, z));

        _colors.Add((Color)cSD);
        _colors.Add((Color)cND);
        _colors.Add((Color)cNU);
        _colors.Add((Color)cSU);

        _normals.Add(Vector3.left);
        _normals.Add(Vector3.left);
        _normals.Add(Vector3.left);
        _normals.Add(Vector3.left);

        _uvs.Add(new Vector2(High(-wz + 1), Low(wy)));
        _uvs.Add(new Vector2(Low(-wz), Low(wy)));
        _uvs.Add(new Vector2(Low(-wz), High(wy + 1)));
        _uvs.Add(new Vector2(High(-wz + 1), High(wy + 1)));

        _triangles.Add(v + 0);
        _triangles.Add(v + 1);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 3);
        _triangles.Add(v + 0);
    }

    public void AppendWestFaceCollider(float x, float y, float z, int ySize, int zSize)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, y, z));
        _vertices.Add(new Vector3(x, y, z + zSize));
        _vertices.Add(new Vector3(x, y + ySize, z + zSize));
        _vertices.Add(new Vector3(x, y + ySize, z));

        _triangles.Add(v + 0);
        _triangles.Add(v + 1);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 3);
        _triangles.Add(v + 0);
    }
    #endregion

    #region Eastern faces
    public void AppendEastFace(float x, float y, float z, int ySize, int zSize, LightColor cSD, LightColor cND, LightColor cNU, LightColor cSU, float wy, float wz)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, y, z));
        _vertices.Add(new Vector3(x, y, z + zSize));
        _vertices.Add(new Vector3(x, y + ySize, z + zSize));
        _vertices.Add(new Vector3(x, y + ySize, z));

        _colors.Add((Color)cSD);
        _colors.Add((Color)cND);
        _colors.Add((Color)cNU);
        _colors.Add((Color)cSU);

        _normals.Add(Vector3.right);
        _normals.Add(Vector3.right);
        _normals.Add(Vector3.right);
        _normals.Add(Vector3.right);

        _uvs.Add(new Vector2(Low(wz - zSize), Low(wy)));
        _uvs.Add(new Vector2(High(wz), Low(wy)));
        _uvs.Add(new Vector2(High(wz), High(wy + ySize)));
        _uvs.Add(new Vector2(Low(wz - zSize), High(wy + ySize)));

        _triangles.Add(v + 0);
        _triangles.Add(v + 3);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 1);
        _triangles.Add(v + 0);
    }

    public void AppendEastFaceWater(float x, float z, float yD, float yUS, float yUN, LightColor cSD, LightColor cND, LightColor cNU, LightColor cSU, float wy, float wz)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, yD, z));
        _vertices.Add(new Vector3(x, yD, z + 1));
        _vertices.Add(new Vector3(x, yUN, z + 1));
        _vertices.Add(new Vector3(x, yUS, z));

        _colors.Add((Color)cSD);
        _colors.Add((Color)cND);
        _colors.Add((Color)cNU);
        _colors.Add((Color)cSU);

        _normals.Add(Vector3.right);
        _normals.Add(Vector3.right);
        _normals.Add(Vector3.right);
        _normals.Add(Vector3.right);

        _uvs.Add(new Vector2(Low(wz - 1), Low(wy)));
        _uvs.Add(new Vector2(High(wz), Low(wy)));
        _uvs.Add(new Vector2(High(wz), High(wy + 1)));
        _uvs.Add(new Vector2(Low(wz - 1), High(wy + 1)));

        _triangles.Add(v + 0);
        _triangles.Add(v + 3);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 1);
        _triangles.Add(v + 0);
    }

    public void AppendEastFaceCollider(float x, float y, float z, int ySize, int zSize)
    {
        var v = _vertices.Count;
        _vertices.Add(new Vector3(x, y, z));
        _vertices.Add(new Vector3(x, y, z + zSize));
        _vertices.Add(new Vector3(x, y + ySize, z + zSize));
        _vertices.Add(new Vector3(x, y + ySize, z));

        _triangles.Add(v + 0);
        _triangles.Add(v + 3);
        _triangles.Add(v + 2);
        _triangles.Add(v + 2);
        _triangles.Add(v + 1);
        _triangles.Add(v + 0);
    }
    #endregion

    #region Private

    private Vector4[] CalculateTangents()
    {
        int triangleCount = _triangles.Count;
        int vertexCount = _vertices.Count;

        var tan1 = new Vector3[vertexCount];
        var tan2 = new Vector3[vertexCount];

        var tangents = new Vector4[vertexCount];

        for (int a = 0; a < triangleCount; a += 3)
        {
            int i1 = _triangles[a + 0];
            int i2 = _triangles[a + 1];
            int i3 = _triangles[a + 2];

            var v1 = _vertices[i1];
            var v2 = _vertices[i2];
            var v3 = _vertices[i3];

            var w1 = _uvs[i1];
            var w2 = _uvs[i2];
            var w3 = _uvs[i3];

            float x1 = v2.x - v1.x;
            float x2 = v3.x - v1.x;
            float y1 = v2.y - v1.y;
            float y2 = v3.y - v1.y;
            float z1 = v2.z - v1.z;
            float z2 = v3.z - v1.z;

            float s1 = w2.x - w1.x;
            float s2 = w3.x - w1.x;
            float t1 = w2.y - w1.y;
            float t2 = w3.y - w1.y;

            float r = 1.0f / (s1 * t2 - s2 * t1);

            var sdir = new Vector3((t2 * x1 - t1 * x2) * r, (t2 * y1 - t1 * y2) * r, (t2 * z1 - t1 * z2) * r);
            var tdir = new Vector3((s1 * x2 - s2 * x1) * r, (s1 * y2 - s2 * y1) * r, (s1 * z2 - s2 * z1) * r);

            tan1[i1] += sdir;
            tan1[i2] += sdir;
            tan1[i3] += sdir;

            tan2[i1] += tdir;
            tan2[i2] += tdir;
            tan2[i3] += tdir;
        }


        for (int a = 0; a < vertexCount; ++a)
        {
            var n = _normals[a];
            var t = tan1[a];

            var tmp = (t - n * Vector3.Dot(n, t)).normalized;
            tangents[a] = new Vector4(tmp.x, tmp.y, tmp.z);
            tangents[a].w = Vector3.Dot(Vector3.Cross(n, t), tan2[a]) < 0.0f ? -1.0f : 1.0f;
        }

        return tangents;
    }

    private int AppendGeometry(Vector3 position, IEnumerable<Vector3> vertices, IEnumerable<Vector3> normals, IEnumerable<Vector2> uvs, IEnumerable<Color> colors, IEnumerable<int> triangles)
    {
        var v = _vertices.Count;

        foreach (var vertex in vertices)
        {
            _vertices.Add(position + vertex);
        }

        _colors.AddRange(colors);
        _normals.AddRange(normals);
        _uvs.AddRange(uvs);

        foreach (var triangle in triangles)
        {
            _triangles.Add(v + triangle);
        }

        return v;
    }

    private const float LIMIT = 4;

    private static float Low(float a)
    {
        return (a + 65536) % LIMIT;
    }

    private static float High(float a)
    {
        var b = (a + 65536) % LIMIT;
        if (b < .0001f)
        {
            return LIMIT;
        }
        return b;
    }

    #endregion
}