Atoms supports blend shapes deformation. In order to use blend shapes during the simulation the blend shapes target must be exported using the export mesh tool. The export mesh tool writes the P, N, id and name information of each target inside the mesh file.vThe variation builder automatically exports the blend shapes information, so if you created your variation with the variation builder you have already all setup.
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You can add these metadatas usign the "addMetadata" behaviour or you can animate the blend shapes using the blendShapeAnim module, please have a look to the tutorial section.