Alembic
The Alembic object contains links to the Alembic file, which means that any changes made to this file will be assumed by Cinema 4D. Objects can be switched for rendering (e.g., low-poly dummy objects can be replaced by high-poly objects for rendering). The object type must, however, be the same! For example, you cannot switch a Spline object with a mesh.
Normally an "a" on a white background will be displayed at the bottom left. If the link is not found (e.g., if the name of the Alembic file or the Object ID was modified), this background will be red.
If the Alembic object is made editable (C key), the geometry will remain non-animated in its current animation state.
Selection Tag
The functions described below will only work correctly as long as the number of points/polygons of the Alembic object are not modified.
Textures
If Facet Sets (polygon selections) are saved in the Alembic file, these can be used in Cinema 4D by entering the name of the Selection tag listed as a (invisible) tab in the Attribute Manager in the Selection field.
Creating custom Selection tags for Alembic objects
Proceed as follows if you want to create custom Selection tags for Alembic objects: Duplicate the respective Alembic object, make it editable (c key), make your selection, save the selection and copy the corresponding Selection tag to the original Alembic object. These custom Selection tags will be evaluated correctly (these can, for example, be used for texturing as described above).