在c#中按每个Bolygon的材质分割网格

Question

我有一个包含 FBX 网格日期的类

其中 VertexData 具有顶点数据，例如位置、uv、颜色...等

材质有这个网格的材质

VertexIndices 是三角形面索引

MaterialIndices 是每个三角形的材质索引

我希望能够通过 bolygon 材质将 FBXMeshData 拆分为列表

public class FBXMeshData
{
    public string Name { get; set; }
    public Vector3 Position { get; set; }
    public Vector3 Rotation { get; set; }
    public Vector3 Scale { get; set; }

    private List<FBXVertexData> VertexData { get; set; }

    public List<FBXMaterialData> Materials { get; set; } = new List<FBXMaterialData>();
    private List<int> VertexIndices { get; set; }

    public List<int> MaterialIndices { get; set; }
    public FBXMeshData(FBXMeshData meshData)
    {
        Name = meshData.Name;
        Position = meshData.Position;
        Rotation = meshData.Rotation;
        Scale = meshData.Scale;
        VertexData = meshData.VertexData.Select(x =>
                new FBXVertexData(x.Position, x.Normal, x.Tangents, x.UVs, x.Colors, x.BoneNames.ToArray(),
                    x.BoneWeights.ToArray()))
            .ToList();
        VertexIndices = meshData.VertexIndices;
        MaterialIndices = meshData.MaterialIndices;
        if (meshData.MaterialIndices != null)
        {
            for (int i = 0; i < meshData.Materials.Count; i++)
            {
                Materials.Add(meshData.Materials[i]);
            }
        }

    }

    public FBXMeshData(FbxMeshData meshData)
    {
        Name = meshData.Name;
        Position = MySF.ToVector3(meshData.Position);
        Rotation = MySF.QToYawPitchRoll(meshData.Rotation);
        Scale = MySF.ToVector3(meshData.Scale);
        VertexData = meshData.VertexData.Select(x =>
                new FBXVertexData(x.Position, x.Normal, x.Tangents, x.UVs, x.Colors, x.BoneNames.ToArray(),
                    x.BoneWeights.ToArray()))
            .ToList();
        VertexIndices = meshData.VertexIndices;
        MaterialIndices = meshData.MaterialIndices;
        if (meshData.MaterialIndices != null)
        {
            for (int i = 0; i < meshData.MaterialData.Count; i++)
            {
                Materials.Add(new FBXMaterialData(meshData.MaterialData[i]));
            }
        }
    }
}

我的想法：MaterialIndices中的每个materialindex都指向由VertexIndices中的三个整数组成的多边形，每个整数是VertexData中一个Vertex的索引

首先我检查网格是否有材质或没有材质，然后按原样返回网格 如果不 按材质索引按多边形索引对顶点进行分组 字典

>>>materialToFacetoVertex = 新字典>>>(); 所以每种材质都有一个面列表，每个面都有它的顶点

为每个材质组创建一个新的网格

        public static List<FBXMeshData> SplitByMaterial(FBXMeshData meshData)
        {

            if (meshData.Materials.Count == 0 || meshData.Materials.Count == 1)
            {
                return new List<FBXMeshData> { meshData };
            }

            // Group vertices by polygon index and material index
            var materialToFaceToVertex = new Dictionary<int, Dictionary<int, List<FBXVertexData>>>();
            //int faceindex = 0;
            for (int i = 0; i < meshData.MaterialIndices.Count; i++)
            {
                int materialIndex = meshData.MaterialIndices[i];
               
                FBXVertexData vertex = meshData.VertexData[meshData.VertexIndices[i]];
                FBXVertexData vertex1 = meshData.VertexData[meshData.VertexIndices[i+1]];
                FBXVertexData vertex2 = meshData.VertexData[meshData.VertexIndices[i+2]];
                int faceindex =i;


                if (!materialToFaceToVertex.TryGetValue(materialIndex, out var faceToVertex))
                {
                    faceToVertex = new Dictionary<int, List<FBXVertexData>>();
                    materialToFaceToVertex[materialIndex] = faceToVertex;
                }

                if (!faceToVertex.TryGetValue(faceindex, out var vertexList))
                {
                    vertexList = new List<FBXVertexData>();
                    faceToVertex[faceindex] = vertexList;
                }
                vertexList.Add(vertex);
                vertexList.Add(vertex1);
                vertexList.Add(vertex2);
            }

            // Create separate mesh data for each material group
            var meshList = new List<FBXMeshData>();

            foreach (var kvp in materialToFaceToVertex)
            {
                var materialIndex = kvp.Key;
                var faceToVertex = kvp.Value;
                FBXMaterialData materialData = meshData.Materials[kvp.Key];
                string materialName = materialData.Name;
                var newMeshData = new FBXMeshData(meshData)
                {
                    Name = materialName,
                    Materials = new List<FBXMaterialData> { materialData },
                    VertexData = new List<FBXVertexData>(),
                    VertexIndices = new List<int>(),
                    MaterialIndices = new List<int> { 0 },
                    
                  

                 };
               
                int currentvertindex = 0;
                foreach (var faceVertices in faceToVertex.Values)
                {
                    newMeshData.VertexData.AddRange(faceVertices);

                    // Add indices for the current triangle (assuming triangles)
                    newMeshData.VertexIndices.Add(currentvertindex);
                    newMeshData.VertexIndices.Add(currentvertindex + 1);
                    newMeshData.VertexIndices.Add(currentvertindex + 2);

                    currentvertindex += 3; // Increment by 3 for each triangle's vertices
                }



                meshList.Add(newMeshData);
            }
            StringBuilder sb = new StringBuilder();
            foreach (var mes in meshList)
            {
                sb.AppendLine(mes.ToString());
            }




            MainWindow.debug.texView.Text = sb.ToString();
            return meshList;
        }

但是此方法的输出有重复的顶点且索引错误

有人可以帮我吗？

图像显示了一个简单立方体的结果，其中每两个三角形（四边形）都有单独的材质

顺便说一句，这是我如何从 fbx sdk 获取材质索引

    List<int>^ FbxSceneData::GetMaterialIndices(FbxMesh* fbxMesh)
    {
        List<int>^ materialIndices = gcnew List<int>();

        FbxLayerElementMaterial* materialLayer = fbxMesh->GetLayer(0)->GetMaterials();

        if (materialLayer)
        {
            FbxLayerElement::EMappingMode mappingMode = materialLayer->GetMappingMode();
            if (mappingMode == FbxLayerElement::eByPolygon)
            {
                int polygonCount = fbxMesh->GetPolygonCount();
                for (int p = 0; p < polygonCount; p++)
                {
                    int materialIndex = materialLayer->GetIndexArray().GetAt(p);
                    materialIndices->Add(materialIndex);

                    // Now you have the material index for this polygon
                  // You can use it to retrieve the material for further processing
                  // FbxSurfaceMaterial* material = mesh->GetNode()->GetMaterial(materialIndex);
                  // ... (do something with the material index)

                }
            }
            else if (mappingMode == FbxLayerElement::eAllSame)
            {
                // In this case, all polygons share the same material, and the material index is 0
                int materialIndex = materialLayer->GetIndexArray().GetAt(0);
                materialIndices->Add(materialIndex);
            }
            else
            {
                // Other mapping modes are not supported in this example
            }
        }
        else
        {
            // The mesh does not have any material information
        }

        return materialIndices;
    }

Answer 1

我可以轻松地在一个 linq 语句中创建字典。但是你的类必须正确定义。每个顶点都必须有一个材质。类应该是这样的

    public class FBXMeshData
    {
        public string Name { get; set; }
        public Vector3 Position { get; set; }
        public Vector3 Rotation { get; set; }
        public Vector3 Scale { get; set; }

        private List<FBXVertexData> VertexData { get; set; }

    }
    public class FBXMaterialData
    {

    }
    public class FBXVertexData
    {
        FBXMaterialData material { get; set; }

    }