Mesh perimeter edges

I want to know when to draw the edges in a mesh.

I can get the normals of the two faces:[1].data.polygons[0].normal[1].data.polygons[1].normal

If the angle between them is >= 90 degrees, then the line is visible.

I can use


to get the angle.

But I obviously also need to draw the line if the edge is a perimeter line with reference to the camera.

For this I would need the direction the camera is looking.

What else do I need?