# GeometryProcessing/Spring2009/Schedule/Spectral Processing4

### From VisTrailsWiki

- Brad Loos

Okay, what is isometry, as in *symmetries of a shape which are invariant up to isometry*. Is there a more technical definition than just something that is the same about a shape even if you rotate/scale/animate it?

- Manasi Datar

Is the Green's function using the distance as a 'measure' of covariance in some sense ?

Secondly, is there a concept similar to Mutual Information (used to measure similarity/correspondence while aligning images), defined for meshes ? It may not work in all cases, but could help eliminate naive one-to-one matching !