Baked Hair Shape
Baked Hair shape stores a complete hair object and acts as a base object to which other hair operators can be added. You can get baked hair object by collapsing an existing procedurally created hair stack, or importing hair from an external file. A sub-set of baked hair is previewed inside the viewport and this amount of hairs previewed can be controlled via a parameter.
Parameters
Distribution Mesh
Baked hair can contain "surface dependency" information about how it attaches to a mesh surface. If this information is present you can set the distribution mesh from a scene by pressing this button and the hair will attach to this surface and follow it as it deforms. The surface will also be passed down the evaluation pipeline to be used with other operators.
An alternative to setting the distribution mesh here is to use the Ground Strands node and ground the strands. This can be done, for example, if the hair was imported from an Alembic file instead of being collapsed from an operator stack.
Display Fraction
Fraction of final render hairs which is displayed inside the viewport. Reducing this parameter below 1 will display a sub-set of render hairs inside the viewport. This is useful for speeding up viewport hair preview.
File X Name
This set of file paths text boxes allows you to select one or more Alembic .abc files to be referenced by this Baked Hair operator. The hair within the .abc file will be loaded along with any additional information like widths, texture coordinates, strand groups, and strand data. Specifying multiple files will merge the hair within those files into a single output hair object.
This field is automatically set when importing Alembic hair.
Reload from File
Pressing this button will clear internal data and re-load the hair from any specified Alembic files through the File X Name textboxes.
Attach Roots
Similar to Ground Strands operator this button will attach or detach the hair roots to specified Distribution Mesh surface. Attaching roots will project all of the hair roots onto the mesh, generating new surface dependency information.
Position Blend Ramp
Similar to Ground Strands operator this curve allows specifying, along strand length, which points will be moved to be on the distribution mesh surface and which points will remain in their original positions unaffected.
Ground Closest End
When on, the closest end (tip or root) of the baked hair will be grounded to the base surface
Set Texture Coordinates
When on, texture coordinates from the base surface will be assigned to the baked hair
Dynamic Grounding
When on, hair will be automatically grounded if their count or order changes. For example, when rendering the render count of the hair will be grounded right before it is evaluated.