Merge Operator
The Merge operator combines two or more hair or guide objects into a single object. It is useful when parts of a groom are generated and styled separately - for example a character's body fur and head hair built on the same surface - and you want them to become one groom without losing the separate creation history of each.
How merging works
Add the Merge operator at the point in the stack where you want the inputs to come together, and provide the objects to merge. From that point up, the groom is the combined result. Operators placed below the merge still affect only their own input; operators above it act on the merged whole.
Same distribution surface
Merging assumes that all of the inputs were planted on the same distribution surface. Keeping the inputs on a shared surface ensures their roots and surface data line up, so the merged groom behaves consistently.
Keeping parts distinct
Once the inputs are merged, their strands are only distinguishable by their strand groups, and each input brings its own group numbering with it. Groups coming from different inputs therefore overlap: two inputs which both use group 1 cannot be told apart afterwards, and inputs carrying no strand groups at all end up in group 0.
Turn on Concatenate Strand Groups to have the merge renumber them. Every merged input receives a range of group values that no other input uses, so an operator placed above the merge can target one input's strands on their own. An input which carries no strand groups of its own counts as a single group, so merging several plain hair objects gives one group per object.
The option is off by default, and the object the Merge operator sits on keeps the groups it already had - only the merged inputs are renumbered.
You can also assign the inputs different strand groups by hand before or after the merge, then target those groups with later operators.
Related
- Working with Strand Groups - keep merged parts addressable.
- Groom Operator - encapsulate a sub-groom as a single unit.