MeshData.py 文件源码

def faceNormals(self, indexed=None):
        """
        Return an array (Nf, 3) of normal vectors for each face.
        If indexed='faces', then instead return an indexed array
        (Nf, 3, 3)  (this is just the same array with each vector
        copied three times).
        """
        if self._faceNormals is None:
            v = self.vertexes(indexed='faces')
            self._faceNormals = np.cross(v[:,1]-v[:,0], v[:,2]-v[:,0])

        if indexed is None:
            return self._faceNormals
        elif indexed == 'faces':
            if self._faceNormalsIndexedByFaces is None:
                norms = np.empty((self._faceNormals.shape[0], 3, 3))
                norms[:] = self._faceNormals[:,np.newaxis,:]
                self._faceNormalsIndexedByFaces = norms
            return self._faceNormalsIndexedByFaces
        else:
            raise Exception("Invalid indexing mode. Accepts: None, 'faces'")