Sentence:  In order to be saved , plasticity had had to be isolated ; and as the aspect of the subject was transposed into those clusters of more or less interchangeable and contour obliterating <WSD>facet-planes</WSD> by which plasticity was isolated under the Cubist method , the subject itself became largely unrecognizable . 
Meaning of the word marked with <WSD> tags:  the plane of a facet of an object (as of a cube)