normals calculations

MeshParams_vec_sp buildExtractedMesh(TerrainThreadRequest_sp threadReq) {
    int materialCount = threadReq->terrainMaterials->Num();
    MeshParams_vec_sp meshParams_vec_sp = MakeShareable(new std::vector<MeshParams>(materialCount));
    threadReq->location_cm = getLocFromRegionLoc(threadReq->regionWidth, threadReq->regionLoc);
    int chunkCounter = 0;
    PolyVox::Mesh<PolyVox::Vertex<MDP88>, unsigned int> DecodedMesh;
    if (threadReq->smooth) {
        //auto DecodedMesh = decodeMesh(threadReq->marchingExtractedMesh);
        DecodedMesh = decodeMesh(threadReq->marchingExtractedMesh);
    }
    else {
        DecodedMesh = decodeMesh(threadReq->cubicExtractedMesh);
    }

    for (int Material = 0; Material < materialCount; Material++)
    {
        MeshParams* mp = &meshParams_vec_sp->data()[Material];
        mp->material_index = Material;
        mp->location = threadReq->location_cm;
        mp->colliderEnabled = true;
        // Loop over all of the triangle vertex indices
        for (uint32 i = 0; i < DecodedMesh.getNoOfIndices() - 2; i += 3)
        {
            // We need to add the vertices of each triangle in reverse or the mesh will be upside down
            auto Index = DecodedMesh.getIndex(i + 2);
            auto Vertex2 = DecodedMesh.getVertex(Index);
            auto TriangleMaterial = Vertex2.data.getMaterial();

            // Before we continue, we need to be sure that the triangle is the right material; we don't want to use verticies from other materials
            if (TriangleMaterial == (Material + 1))
            {
                // If it is of the same material, then we need to add the correct indices now
                mp->Indices.Add(mp->Vertices.Add(FPolyVoxVector(Vertex2.position) * 100.f));

                Index = DecodedMesh.getIndex(i + 1);
                auto Vertex1 = DecodedMesh.getVertex(Index);
                mp->Indices.Add(mp->Vertices.Add(FPolyVoxVector(Vertex1.position) * 100.f));

                Index = DecodedMesh.getIndex(i);
                auto Vertex0 = DecodedMesh.getVertex(Index);
                mp->Indices.Add(mp->Vertices.Add(FPolyVoxVector(Vertex0.position) * 100.f));

                // Calculate the tangents of our triangle
                const FVector Edge01 = FPolyVoxVector(Vertex1.position - Vertex0.position);
                const FVector Edge02 = FPolyVoxVector(Vertex2.position - Vertex0.position);

                const FVector TangentX = Edge01.GetSafeNormal();
                FVector TangentZ = (Edge01 ^ Edge02).GetSafeNormal();

                for (int32 i = 0; i < 3; i++)
                {
                    mp->Tangents.Add(FRuntimeMeshTangent(TangentX, false));
                    mp->Normals.Add(TangentZ);
                }
            }
        }
    }


    return meshParams_vec_sp;
}