Hi,

How mesh faces normals are normally calculated?

I want to get ngon face normal.

I used method below. But I see it does work only for one polyline, but not on full mesh.

To get a plane origin I sum up all boundary vertices and divided by number of them.

Then for normal vector I thought I could do the same by summing up all vertex normals and dividing by number of them.

But this does not produce normal perpendicular planar ngon face.

Before I was using this method:

```
public static Plane[] GetNgonPlanes(this Mesh mesh)
{
Plane[] p = new Plane[mesh.Ngons.Count];
uint[][] b = mesh.GetNGonsBoundaries(); //extension method
for (int i = 0; i < mesh.Ngons.Count; i++)
{
Vector3f temp = new Vector3f();
for (int j = 0; j < b[i].Length; j++)
temp += mesh.Normals[(int)b[i][j]];
if (b[i].Length > 0)
temp /= b[i].Length;
p[i] = new Plane(mesh.Ngons.GetNgonCenter(i), temp); //Extension method
}
return p;
}
```