GeometryMeshNormals Property

Gets or sets an array of Vector3 that defines the normals for this mesh. When Normals property value or the data in the normals array are changed and if this mesh was already initialized (IsInitialized is true) then you need to call UpdateMesh or UpdateMesh(BoundingBox) method for the changes to take effect.

public Vector3[]? Normals { get; set; }