BlockMesh.cs

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using System.Runtime.InteropServices;
using Engine;
using Engine.Graphics;
using Engine.Media;
 
namespace Game {
    public class BlockMesh {
        public struct InternalVertex {
            public Vector3 Position;
 
            public Vector3 Normal;
 
            public Vector2 TextureCoordinate;
        }
 
        public DynamicArray<BlockMeshVertex> Vertices = [];
 
        public DynamicArray<int> Indices = [];
 
        public DynamicArray<sbyte> Sides;
 
        public object m_tag;
 
        public object Tag {
            get => m_tag;
            set => m_tag = value;
        }
 
        public virtual BoundingBox CalculateBoundingBox() {
            return new BoundingBox(Vertices.Select(v => v.Position));
        }
 
        public virtual BoundingBox CalculateBoundingBox(Matrix matrix) {
            return new BoundingBox(Vertices.Select(v => Vector3.Transform(v.Position, matrix)));
        }
 
        public static Matrix GetBoneAbsoluteTransform(ModelBone modelBone) {
            if (modelBone.ParentBone != null) {
                return GetBoneAbsoluteTransform(modelBone.ParentBone) * modelBone.Transform;
            }
            return modelBone.Transform;
        }
 
        public virtual void AppendImageExtrusion(Image image, Rectangle bounds, Vector3 size, Color color) {
            BlockMesh blockMesh = new();
            DynamicArray<BlockMeshVertex> vertices = blockMesh.Vertices;
            DynamicArray<int> indices = blockMesh.Indices;
            BlockMeshVertex item = new() {
                Position = new Vector3(bounds.Left, bounds.Top, -1f), TextureCoordinates = new Vector2(bounds.Left, bounds.Top)
            };
            vertices.Add(item);
            item = new BlockMeshVertex {
                Position = new Vector3(bounds.Right, bounds.Top, -1f), TextureCoordinates = new Vector2(bounds.Right, bounds.Top)
            };
            vertices.Add(item);
            item = new BlockMeshVertex {
                Position = new Vector3(bounds.Left, bounds.Bottom, -1f), TextureCoordinates = new Vector2(bounds.Left, bounds.Bottom)
            };
            vertices.Add(item);
            item = new BlockMeshVertex {
                Position = new Vector3(bounds.Right, bounds.Bottom, -1f), TextureCoordinates = new Vector2(bounds.Right, bounds.Bottom)
            };
            vertices.Add(item);
            indices.Add(vertices.Count - 4);
            indices.Add(vertices.Count - 1);
            indices.Add(vertices.Count - 3);
            indices.Add(vertices.Count - 1);
            indices.Add(vertices.Count - 4);
            indices.Add(vertices.Count - 2);
            item = new BlockMeshVertex {
                Position = new Vector3(bounds.Left, bounds.Top, 1f), TextureCoordinates = new Vector2(bounds.Left, bounds.Top)
            };
            vertices.Add(item);
            item = new BlockMeshVertex {
                Position = new Vector3(bounds.Right, bounds.Top, 1f), TextureCoordinates = new Vector2(bounds.Right, bounds.Top)
            };
            vertices.Add(item);
            item = new BlockMeshVertex {
                Position = new Vector3(bounds.Left, bounds.Bottom, 1f), TextureCoordinates = new Vector2(bounds.Left, bounds.Bottom)
            };
            vertices.Add(item);
            item = new BlockMeshVertex {
                Position = new Vector3(bounds.Right, bounds.Bottom, 1f), TextureCoordinates = new Vector2(bounds.Right, bounds.Bottom)
            };
            vertices.Add(item);
            indices.Add(vertices.Count - 4);
            indices.Add(vertices.Count - 3);
            indices.Add(vertices.Count - 1);
            indices.Add(vertices.Count - 1);
            indices.Add(vertices.Count - 2);
            indices.Add(vertices.Count - 4);
            for (int i = bounds.Left - 1; i <= bounds.Right; i++) {
                int num = -1;
                for (int j = bounds.Top - 1; j <= bounds.Bottom; j++) {
                    bool num2 = !bounds.Contains(new Point2(i, j)) || image.GetPixelFast(i, j).IsCompletelyTransparent();
                    bool flag = bounds.Contains(new Point2(i - 1, j)) && !image.GetPixelFast(i - 1, j).IsCompletelyTransparent();
                    if (num2 & flag) {
                        if (num < 0) {
                            num = j;
                        }
                    }
                    else if (num >= 0) {
                        item = new BlockMeshVertex {
                            Position = new Vector3(i - 0.01f, num - 0.01f, -1.01f), TextureCoordinates = new Vector2(i - 1 + 0.01f, num + 0.01f)
                        };
                        vertices.Add(item);
                        item = new BlockMeshVertex {
                            Position = new Vector3(i - 0.01f, num - 0.01f, 1.01f), TextureCoordinates = new Vector2(i - 0.01f, num + 0.01f)
                        };
                        vertices.Add(item);
                        item = new BlockMeshVertex {
                            Position = new Vector3(i - 0.01f, j + 0.01f, -1.01f), TextureCoordinates = new Vector2(i - 1 + 0.01f, j - 0.01f)
                        };
                        vertices.Add(item);
                        item = new BlockMeshVertex {
                            Position = new Vector3(i - 0.01f, j + 0.01f, 1.01f), TextureCoordinates = new Vector2(i - 0.01f, j - 0.01f)
                        };
                        vertices.Add(item);
                        indices.Add(vertices.Count - 4);
                        indices.Add(vertices.Count - 1);
                        indices.Add(vertices.Count - 3);
                        indices.Add(vertices.Count - 1);
                        indices.Add(vertices.Count - 4);
                        indices.Add(vertices.Count - 2);
                        num = -1;
                    }
                }
            }
            for (int k = bounds.Left - 1; k <= bounds.Right; k++) {
                int num3 = -1;
                for (int l = bounds.Top - 1; l <= bounds.Bottom; l++) {
                    bool num4 = !bounds.Contains(new Point2(k, l)) || image.GetPixelFast(k, l).IsCompletelyTransparent();
                    bool flag2 = bounds.Contains(new Point2(k + 1, l)) && !image.GetPixelFast(k + 1, l).IsCompletelyTransparent();
                    if (num4 & flag2) {
                        if (num3 < 0) {
                            num3 = l;
                        }
                    }
                    else if (num3 >= 0) {
                        item = new BlockMeshVertex {
                            Position = new Vector3(k + 1 + 0.01f, num3 - 0.01f, -1.01f), TextureCoordinates = new Vector2(k + 1 + 0.01f, num3 + 0.01f)
                        };
                        vertices.Add(item);
                        item = new BlockMeshVertex {
                            Position = new Vector3(k + 1 + 0.01f, num3 - 0.01f, 1.01f), TextureCoordinates = new Vector2(k + 2 - 0.01f, num3 + 0.01f)
                        };
                        vertices.Add(item);
                        item = new BlockMeshVertex {
                            Position = new Vector3(k + 1 + 0.01f, l + 0.01f, -1.01f), TextureCoordinates = new Vector2(k + 1 + 0.01f, l - 0.01f)
                        };
                        vertices.Add(item);
                        item = new BlockMeshVertex {
                            Position = new Vector3(k + 1 + 0.01f, l + 0.01f, 1.01f), TextureCoordinates = new Vector2(k + 2 - 0.01f, l - 0.01f)
                        };
                        vertices.Add(item);
                        indices.Add(vertices.Count - 4);
                        indices.Add(vertices.Count - 3);
                        indices.Add(vertices.Count - 1);
                        indices.Add(vertices.Count - 1);
                        indices.Add(vertices.Count - 2);
                        indices.Add(vertices.Count - 4);
                        num3 = -1;
                    }
                }
            }
            for (int m = bounds.Top - 1; m <= bounds.Bottom; m++) {
                int num5 = -1;
                for (int n = bounds.Left - 1; n <= bounds.Right; n++) {
                    bool num6 = !bounds.Contains(new Point2(n, m)) || image.GetPixelFast(n, m).IsCompletelyTransparent();
                    bool flag3 = bounds.Contains(new Point2(n, m - 1)) && !image.GetPixelFast(n, m - 1).IsCompletelyTransparent();
                    if (num6 & flag3) {
                        if (num5 < 0) {
                            num5 = n;
                        }
                    }
                    else if (num5 >= 0) {
                        item = new BlockMeshVertex {
                            Position = new Vector3(num5 - 0.01f, m - 0.01f, -1.01f), TextureCoordinates = new Vector2(num5 + 0.01f, m - 1 + 0.01f)
                        };
                        vertices.Add(item);
                        item = new BlockMeshVertex {
                            Position = new Vector3(num5 - 0.01f, m - 0.01f, 1.01f), TextureCoordinates = new Vector2(num5 + 0.01f, m - 0.01f)
                        };
                        vertices.Add(item);
                        item = new BlockMeshVertex {
                            Position = new Vector3(n + 0.01f, m - 0.01f, -1.01f), TextureCoordinates = new Vector2(n - 0.01f, m - 1 + 0.01f)
                        };
                        vertices.Add(item);
                        item = new BlockMeshVertex {
                            Position = new Vector3(n + 0.01f, m - 0.01f, 1.01f), TextureCoordinates = new Vector2(n - 0.01f, m - 0.01f)
                        };
                        vertices.Add(item);
                        indices.Add(vertices.Count - 4);
                        indices.Add(vertices.Count - 3);
                        indices.Add(vertices.Count - 1);
                        indices.Add(vertices.Count - 1);
                        indices.Add(vertices.Count - 2);
                        indices.Add(vertices.Count - 4);
                        num5 = -1;
                    }
                }
            }
            for (int num7 = bounds.Top - 1; num7 <= bounds.Bottom; num7++) {
                int num8 = -1;
                for (int num9 = bounds.Left - 1; num9 <= bounds.Right; num9++) {
                    bool num10 = !bounds.Contains(new Point2(num9, num7)) || image.GetPixelFast(num9, num7).IsCompletelyTransparent();
                    bool flag4 = bounds.Contains(new Point2(num9, num7 + 1)) && !image.GetPixelFast(num9, num7 + 1).IsCompletelyTransparent();
                    if (num10 & flag4) {
                        if (num8 < 0) {
                            num8 = num9;
                        }
                    }
                    else if (num8 >= 0) {
                        item = new BlockMeshVertex {
                            Position = new Vector3(num8 - 0.01f, num7 + 1 + 0.01f, -1.01f),
                            TextureCoordinates = new Vector2(num8 + 0.01f, num7 + 1 + 0.01f)
                        };
                        vertices.Add(item);
                        item = new BlockMeshVertex {
                            Position = new Vector3(num8 - 0.01f, num7 + 1 + 0.01f, 1.01f),
                            TextureCoordinates = new Vector2(num8 + 0.01f, num7 + 2 - 0.01f)
                        };
                        vertices.Add(item);
                        item = new BlockMeshVertex {
                            Position = new Vector3(num9 + 0.01f, num7 + 1 + 0.01f, -1.01f),
                            TextureCoordinates = new Vector2(num9 - 0.01f, num7 + 1 + 0.01f)
                        };
                        vertices.Add(item);
                        item = new BlockMeshVertex {
                            Position = new Vector3(num9 + 0.01f, num7 + 1 + 0.01f, 1.01f),
                            TextureCoordinates = new Vector2(num9 - 0.01f, num7 + 2 - 0.01f)
                        };
                        vertices.Add(item);
                        indices.Add(vertices.Count - 4);
                        indices.Add(vertices.Count - 1);
                        indices.Add(vertices.Count - 3);
                        indices.Add(vertices.Count - 1);
                        indices.Add(vertices.Count - 4);
                        indices.Add(vertices.Count - 2);
                        num8 = -1;
                    }
                }
            }
            for (int num11 = 0; num11 < vertices.Count; num11++) {
                vertices.Array[num11].Position.X -= bounds.Left + bounds.Width / 2f;
                vertices.Array[num11].Position.Y = bounds.Bottom - vertices.Array[num11].Position.Y - bounds.Height / 2f;
                vertices.Array[num11].Position.X *= size.X / bounds.Width;
                vertices.Array[num11].Position.Y *= size.Y / bounds.Height;
                vertices.Array[num11].Position.Z *= size.Z / 2f;
                vertices.Array[num11].TextureCoordinates.X /= image.Width;
                vertices.Array[num11].TextureCoordinates.Y /= image.Height;
                vertices.Array[num11].Color = color;
            }
            AppendBlockMesh(blockMesh);
        }
 
        public virtual void AppendModelMeshPart(ModelMeshPart meshPart,
            Matrix matrix,
            bool makeEmissive,
            bool flipWindingOrder,
            bool doubleSided,
            bool flipNormals,
            Color color) {
            bool skipVanilla = false;
            ModsManager.HookAction(
                "OnFirstPersonModelDrawing",
                loader => {
                    loader.OnAppendModelMeshPart(
                        this,
                        meshPart,
                        matrix,
                        makeEmissive,
                        flipWindingOrder,
                        doubleSided,
                        flipNormals,
                        color,
                        out bool skip
                    );
                    skipVanilla |= skip;
                    return false;
                }
            );
            if (skipVanilla) {
                return;
            }
            VertexBuffer vertexBuffer = meshPart.VertexBuffer;
            IndexBuffer indexBuffer = meshPart.IndexBuffer;
            ReadOnlyList<VertexElement> vertexElements = vertexBuffer.VertexDeclaration.VertexElements;
            if (vertexElements.Count != 3
                || vertexElements[0].Offset != 0
                || vertexElements[0].Semantic != VertexElementSemantic.Position.GetSemanticString()
                || vertexElements[1].Offset != 12
                || vertexElements[1].Semantic != VertexElementSemantic.Normal.GetSemanticString()
                || vertexElements[2].Offset != 24
                || vertexElements[2].Semantic != VertexElementSemantic.TextureCoordinate.GetSemanticString()) {
                throw new InvalidOperationException("Wrong vertex format for a block mesh.");
            }
            InternalVertex[] vertexData = GetVertexData<InternalVertex>(vertexBuffer);
            int[] indexData = GetIndexData<int>(indexBuffer);
            Dictionary<int, int> dictionary = new();
            for (int i = meshPart.StartIndex; i < meshPart.StartIndex + meshPart.IndicesCount; i++) {
                int num = indexData[i];
                if (!dictionary.ContainsKey(num)) {
                    dictionary.Add(num, Vertices.Count);
                    BlockMeshVertex item = default;
                    item.Position = Vector3.Transform(vertexData[num].Position, matrix);
                    item.TextureCoordinates = vertexData[num].TextureCoordinate;
                    Vector3 vector = Vector3.Normalize(
                        Vector3.TransformNormal(flipNormals ? -vertexData[num].Normal : vertexData[num].Normal, matrix)
                    );
                    if (makeEmissive) {
                        item.IsEmissive = true;
                        item.Color = color;
                    }
                    else {
                        item.Color = color * LightingManager.CalculateLighting(vector);
                        item.Color.A = color.A;
                    }
                    item.Face = (byte)CellFace.Vector3ToFace(vector);
                    Vertices.Add(item);
                }
            }
            for (int j = 0; j < meshPart.IndicesCount / 3; j++) {
                if (doubleSided) {
                    Indices.Add(dictionary[indexData[meshPart.StartIndex + 3 * j]]);
                    Indices.Add(dictionary[indexData[meshPart.StartIndex + 3 * j + 1]]);
                    Indices.Add(dictionary[indexData[meshPart.StartIndex + 3 * j + 2]]);
                    Indices.Add(dictionary[indexData[meshPart.StartIndex + 3 * j]]);
                    Indices.Add(dictionary[indexData[meshPart.StartIndex + 3 * j + 2]]);
                    Indices.Add(dictionary[indexData[meshPart.StartIndex + 3 * j + 1]]);
                }
                else if (flipWindingOrder) {
                    Indices.Add(dictionary[indexData[meshPart.StartIndex + 3 * j]]);
                    Indices.Add(dictionary[indexData[meshPart.StartIndex + 3 * j + 2]]);
                    Indices.Add(dictionary[indexData[meshPart.StartIndex + 3 * j + 1]]);
                }
                else {
                    Indices.Add(dictionary[indexData[meshPart.StartIndex + 3 * j]]);
                    Indices.Add(dictionary[indexData[meshPart.StartIndex + 3 * j + 1]]);
                    Indices.Add(dictionary[indexData[meshPart.StartIndex + 3 * j + 2]]);
                }
            }
            Trim();
        }
 
        public virtual void AppendBlockMesh(BlockMesh blockMesh) {
            bool skipVanilla = false;
            ModsManager.HookAction(
                "OnFirstPersonModelDrawing",
                loader => {
                    loader.OnAppendModelMesh(this, blockMesh, out bool skip);
                    skipVanilla |= skip;
                    return false;
                }
            );
            if (skipVanilla) {
                return;
            }
            int count = Vertices.Count;
            for (int i = 0; i < blockMesh.Vertices.Count; i++) {
                Vertices.Add(blockMesh.Vertices.Array[i]);
            }
            for (int j = 0; j < blockMesh.Indices.Count; j++) {
                Indices.Add(blockMesh.Indices.Array[j] + count);
            }
            Trim();
        }
 
        public virtual void BlendBlockMesh(BlockMesh blockMesh, float factor) {
            if (blockMesh.Vertices.Count != Vertices.Count) {
                throw new InvalidOperationException("Meshes do not match.");
            }
            for (int i = 0; i < Vertices.Count; i++) {
                Vector3 position = Vertices.Array[i].Position;
                Vector3 position2 = blockMesh.Vertices.Array[i].Position;
                Vertices.Array[i].Position = Vector3.Lerp(position, position2, factor);
            }
        }
 
        public virtual void TransformPositions(Matrix matrix, int facesMask = -1) {
            for (int i = 0; i < Vertices.Count; i++) {
                if (((1 << Vertices.Array[i].Face) & facesMask) != 0) {
                    Vertices.Array[i].Position = Vector3.Transform(Vertices.Array[i].Position, matrix);
                }
            }
        }
 
        public virtual void TransformTextureCoordinates(Matrix matrix, int facesMask = -1) {
            for (int i = 0; i < Vertices.Count; i++) {
                if (((1 << Vertices.Array[i].Face) & facesMask) != 0) {
                    Vertices.Array[i].TextureCoordinates = Vector2.Transform(Vertices.Array[i].TextureCoordinates, matrix);
                }
            }
        }
 
        public virtual void SetColor(Color color, int facesMask = -1) {
            for (int i = 0; i < Vertices.Count; i++) {
                if (((1 << Vertices.Array[i].Face) & facesMask) != 0) {
                    Vertices.Array[i].Color = color;
                }
            }
        }
 
        public virtual void ModulateColor(Color color, int facesMask = -1) {
            for (int i = 0; i < Vertices.Count; i++) {
                if (((1 << Vertices.Array[i].Face) & facesMask) != 0) {
                    Vertices.Array[i].Color *= color;
                }
            }
        }
 
        public virtual void GenerateSidesData() {
            Sides = [];
            Sides.Count = Indices.Count / 3;
            for (int i = 0; i < Sides.Count; i++) {
                int num = Indices.Array[3 * i];
                int num2 = Indices.Array[3 * i + 1];
                int num3 = Indices.Array[3 * i + 2];
                Vector3 position = Vertices.Array[num].Position;
                Vector3 position2 = Vertices.Array[num2].Position;
                Vector3 position3 = Vertices.Array[num3].Position;
                if (IsNear(position.Z, position2.Z, position3.Z, 1f)) {
                    Sides.Array[i] = 0;
                }
                else if (IsNear(position.X, position2.X, position3.X, 1f)) {
                    Sides.Array[i] = 1;
                }
                else if (IsNear(position.Z, position2.Z, position3.Z, 0f)) {
                    Sides.Array[i] = 2;
                }
                else if (IsNear(position.X, position2.X, position3.X, 0f)) {
                    Sides.Array[i] = 3;
                }
                else if (IsNear(position.Y, position2.Y, position3.Y, 1f)) {
                    Sides.Array[i] = 4;
                }
                else {
                    Sides.Array[i] = IsNear(position.Y, position2.Y, position3.Y, 0f) ? (sbyte)5 : (sbyte)-1;
                }
            }
        }
 
        public virtual void Trim() {
            Vertices.Capacity = Vertices.Count;
            Indices.Capacity = Indices.Count;
            if (Sides != null) {
                Sides.Capacity = Sides.Count;
            }
        }
 
        public static T[] GetVertexData<T>(VertexBuffer vertexBuffer) where T : unmanaged {
            if (vertexBuffer.Tag is not byte[] array) {
                throw new InvalidOperationException("VertexBuffer does not contain source data in Tag.");
            }
            if (array.Length % Utilities.SizeOf<T>() != 0) {
                throw new InvalidOperationException("VertexBuffer data size is not a whole multiply of target type size.");
            }
            T[] array2 = new T[array.Length / Utilities.SizeOf<T>()];
            GCHandle gCHandle = GCHandle.Alloc(array2, GCHandleType.Pinned);
            try {
                Marshal.Copy(array, 0, gCHandle.AddrOfPinnedObject(), Utilities.SizeOf<T>() * array2.Length);
                return array2;
            }
            finally {
                gCHandle.Free();
            }
        }
 
        public static T[] GetIndexData<T>(IndexBuffer indexBuffer) where T : unmanaged {
            if (indexBuffer.Tag is not byte[] array) {
                throw new InvalidOperationException("IndexBuffer does not contain source data in Tag.");
            }
            if (array.Length % Utilities.SizeOf<T>() != 0) {
                throw new InvalidOperationException("IndexBuffer data size is not a whole multiply of target type size.");
            }
            T[] array2 = new T[array.Length / Utilities.SizeOf<T>()];
            GCHandle gCHandle = GCHandle.Alloc(array2, GCHandleType.Pinned);
            try {
                Marshal.Copy(array, 0, gCHandle.AddrOfPinnedObject(), Utilities.SizeOf<T>() * array2.Length);
                return array2;
            }
            finally {
                gCHandle.Free();
            }
        }
 
        public static bool IsNear(float v1, float v2, float v3, float t) {
            if (v1 - t >= -0.001f
                && v1 - t <= 0.001f
                && v2 - t >= -0.001f
                && v2 - t <= 0.001f
                && v3 - t >= -0.001f) {
                return v3 - t <= 0.001f;
            }
            return false;
        }
 
        public virtual void AppendImageExtrusion(Image image, Rectangle bounds, Vector3 scale, Color color, int alphaThreshold) {
            int count = Vertices.Count;
            AppendImageExtrusionSlice(
                image,
                bounds,
                new Vector3(1f, 0f, 0f),
                new Vector3(0f, 1f, 0f),
                new Vector3(0f, 0f, 1f),
                new Vector3(0f, 0f, 0f),
                color,
                alphaThreshold
            );
            AppendImageExtrusionSlice(
                image,
                bounds,
                new Vector3(1f, 0f, 0f),
                new Vector3(0f, 1f, 0f),
                new Vector3(0f, 0f, -1f),
                new Vector3(0f, 0f, 1f),
                color,
                alphaThreshold
            );
            for (int i = bounds.Left; i < bounds.Right; i++) {
                Image image2 = new(1, bounds.Height);
                for (int j = bounds.Top; j < bounds.Bottom; j++) {
                    if (i == bounds.Left
                        || image.GetPixelFast(i - 1, j).A <= alphaThreshold) {
                        image2.SetPixelFast(0, j - bounds.Top, image.GetPixelFast(i, j));
                    }
                }
                AppendImageExtrusionSlice(
                    image2,
                    new Rectangle(0, 0, image2.Width, image2.Height),
                    new Vector3(0f, 0f, 1f),
                    new Vector3(0f, 1f, 0f),
                    new Vector3(1f, 0f, 0f),
                    new Vector3(i, bounds.Top, 0f),
                    color,
                    alphaThreshold
                );
            }
            for (int k = bounds.Left; k < bounds.Right; k++) {
                Image image3 = new(1, bounds.Height);
                for (int l = bounds.Top; l < bounds.Bottom; l++) {
                    if (k == bounds.Right - 1
                        || image.GetPixelFast(k + 1, l).A <= alphaThreshold) {
                        image3.SetPixelFast(0, l - bounds.Top, image.GetPixelFast(k, l));
                    }
                }
                AppendImageExtrusionSlice(
                    image3,
                    new Rectangle(0, 0, image3.Width, image3.Height),
                    new Vector3(0f, 0f, 1f),
                    new Vector3(0f, 1f, 0f),
                    new Vector3(-1f, 0f, 0f),
                    new Vector3(k + 1, bounds.Top, 0f),
                    color,
                    alphaThreshold
                );
            }
            for (int m = bounds.Top; m < bounds.Bottom; m++) {
                Image image4 = new(bounds.Width, 1);
                for (int n = bounds.Left; n < bounds.Right; n++) {
                    if (m == bounds.Top
                        || image.GetPixelFast(n, m - 1).A <= alphaThreshold) {
                        image4.SetPixelFast(n - bounds.Left, 0, image.GetPixelFast(n, m));
                    }
                }
                AppendImageExtrusionSlice(
                    image4,
                    new Rectangle(0, 0, image4.Width, image4.Height),
                    new Vector3(1f, 0f, 0f),
                    new Vector3(0f, 0f, 1f),
                    new Vector3(0f, 1f, 0f),
                    new Vector3(bounds.Left, m, 0f),
                    color,
                    alphaThreshold
                );
            }
            for (int num = bounds.Top; num < bounds.Bottom; num++) {
                Image image5 = new(bounds.Width, 1);
                for (int num2 = bounds.Left; num2 < bounds.Right; num2++) {
                    if (num == bounds.Bottom - 1
                        || image.GetPixelFast(num2, num + 1).A <= alphaThreshold) {
                        image5.SetPixelFast(num2 - bounds.Left, 0, image.GetPixelFast(num2, num));
                    }
                }
                AppendImageExtrusionSlice(
                    image5,
                    new Rectangle(0, 0, image5.Width, image5.Height),
                    new Vector3(1f, 0f, 0f),
                    new Vector3(0f, 0f, 1f),
                    new Vector3(0f, -1f, 0f),
                    new Vector3(bounds.Left, num + 1, 0f),
                    color,
                    alphaThreshold
                );
            }
            for (int num3 = count; num3 < Vertices.Count; num3++) {
                Vertices.Array[num3].Position.X -= (bounds.Left + bounds.Right) / 2f;
                Vertices.Array[num3].Position.Y -= (bounds.Top + bounds.Bottom) / 2f;
                Vertices.Array[num3].Position.Z -= 0.5f;
                Vertices.Array[num3].Position.X *= scale.X;
                Vertices.Array[num3].Position.Y *= 0f - scale.Y;
                Vertices.Array[num3].Position.Z *= scale.Z;
                Vertices.Array[num3].TextureCoordinates.X /= image.Width;
                Vertices.Array[num3].TextureCoordinates.Y /= image.Height;
                Vertices.Array[num3].Color *= color;
            }
        }
 
        public virtual void AppendImageExtrusionSlice(Image slice,
            Rectangle bounds,
            Vector3 right,
            Vector3 up,
            Vector3 forward,
            Vector3 position,
            Color color,
            int alphaThreshold) {
            int num = int.MaxValue;
            int num2 = int.MaxValue;
            int num3 = int.MinValue;
            int num4 = int.MinValue;
            for (int i = bounds.Top; i < bounds.Bottom; i++) {
                for (int j = bounds.Left; j < bounds.Right; j++) {
                    if (slice.GetPixelFast(j, i).A > alphaThreshold) {
                        num = MathUtils.Min(num, j);
                        num2 = MathUtils.Min(num2, i);
                        num3 = MathUtils.Max(num3, j);
                        num4 = MathUtils.Max(num4, i);
                    }
                }
            }
            if (num != int.MaxValue) {
                Matrix m = new(
                    right.X,
                    right.Y,
                    right.Z,
                    0f,
                    up.X,
                    up.Y,
                    up.Z,
                    0f,
                    forward.X,
                    forward.Y,
                    forward.Z,
                    0f,
                    position.X,
                    position.Y,
                    position.Z,
                    1f
                );
                bool flip = m.Determinant() > 0f;
                float s = LightingManager.CalculateLighting(-forward);
                Vector3 p = Vector3.Transform(new Vector3(num, num2, 0f), m);
                Vector3 p2 = Vector3.Transform(new Vector3(num3 + 1, num2, 0f), m);
                Vector3 p3 = Vector3.Transform(new Vector3(num, num4 + 1, 0f), m);
                Vector3 p4 = Vector3.Transform(new Vector3(num3 + 1, num4 + 1, 0f), m);
                AppendImageExtrusionRectangle(
                    p,
                    p2,
                    p3,
                    p4,
                    forward,
                    flip,
                    Color.MultiplyColorOnly(color, s)
                );
            }
        }
 
        public virtual void AppendImageExtrusionRectangle(Vector3 p11,
            Vector3 p21,
            Vector3 p12,
            Vector3 p22,
            Vector3 forward,
            bool flip,
            Color color) {
            int count = Vertices.Count;
            Vertices.Count += 4;
            int index = Vertices.Count - 4;
            BlockMeshVertex value = new() { Position = p11, TextureCoordinates = p11.XY + forward.XY / 2f, Color = color };
            Vertices[index] = value;
            int index2 = Vertices.Count - 3;
            value = new BlockMeshVertex { Position = p21, TextureCoordinates = p21.XY + forward.XY / 2f, Color = color };
            Vertices[index2] = value;
            int index3 = Vertices.Count - 2;
            value = new BlockMeshVertex { Position = p12, TextureCoordinates = p12.XY + forward.XY / 2f, Color = color };
            Vertices[index3] = value;
            int index4 = Vertices.Count - 1;
            value = new BlockMeshVertex { Position = p22, TextureCoordinates = p22.XY + forward.XY / 2f, Color = color };
            Vertices[index4] = value;
            Indices.Count += 6;
            if (flip) {
                Indices[^6] = count;
                Indices[^5] = count + 2;
                Indices[^4] = count + 1;
                Indices[^3] = count + 2;
                Indices[^2] = count + 3;
                Indices[^1] = count + 1;
            }
            else {
                Indices[^6] = count;
                Indices[^5] = count + 1;
                Indices[^4] = count + 2;
                Indices[^3] = count + 2;
                Indices[^2] = count + 1;
                Indices[^1] = count + 3;
            }
        }
    }
}