OptionalFiles
If an Alembic file contains Cinema 4D instances, you can define here how Cinema 4D should import them (see also Instances).
The color-coded visibility for each object in the Object Manager - top dot for the Viewport, bottom dot for rendering - will be imported from the Alembic file into Cinema 4D if this option is enabled. (see also Visibility)
If enabled, vertex Normals will also be imported - as Normal tags. Otherwise normal Phong shading will be used.
Enable this option if the UV coordinates should be imported as a UVW tag.
Alembic supports polygon selections (which it calls FaceSets). Enabling this option will import these as Polygon Selection tags into Cinema 4D.
Enable this option if you want to import Vertex Maps or Vertex Colors (color maps). Vertex Maps exported by Cinema 4D will be recognized and imported as Vertex Maps.
Note that if Points is set to As Particle Geometry together with existing Vertex Colors, the respective colors will be assumed as Thinking Particles Data Channels. The names are: Vertex Color1(Vector) (color) and Vertex Color2(Real) (alpha).
Alembic files can contain point-based attributes (e.g., velocity, colors, etc.) that Cinema 4D won't necessarily be able to handle. To make use of these attributes, they will be assigned to fitting tags (e.g., vertex colors or vertex maps) if this option is enabled. This can add up to several tags per attribute (one vertex map will, for example, be created per channel). If this option is enabled, these attribues will be assumed. The tags will be named and numbered (per channel) accordingly.