How do I Get the Local Rotation of a Face?

Here is how to obtain the rotation value displayed in the Rotate Transform Type-In box when in the local coordinate system from a face in an Editable Mesh.

GetFaceNormal returns the face normal in local coordinates as a Point3 value.

Multiplied by the transformation matrix of the object, we get the face normal in world space.

Using matrixFromNormal, we create a new matrix3 value using the face normal as the local Z axis. This matrix3 value is rotated relatively to the identity matrix exactly by the values we are searching for.

By converting the matrix3 value toeulerAngles, we retrieve exactly the same 3 values displayed in the Transform Type-In when a face is selected while in Local coordinate system.

SCRIPT

fn getLocalFaceRotation mesh index =
(
  (matrixFromNormal (getFaceNormal mesh index)*mesh.transform ) as eulerAngles
)

obj = sphere() --create a GeoSphere
convertToMesh obj --collapse to EditableMesh
setFaceSelection obj #{38..40, 49, 50, 59, 60, 70, 80} -- select some faces
for f in getFaceSelection obj  do
  format "Face: % - Rotation: % \n" f (getLocalFaceRotation obj f)