Reduce Guides Operator
The Reduce Guides operator picks a small set of strands from dense hair and outputs them as guides. Use it to get simulation guides from a dense or imported groom: reduce the hair to a few hundred guides, simulate them with the Moov Physics Operator, then deform the dense hair with the simulated guides using Adopt External Guides.
How the guides are chosen
Each strand is described by its root and eight points spread evenly along its length. The operator starts from a few random strands and then adds guides in rounds, each time choosing the strands that the current guides reproduce worst from their nearest similar guides. The result covers both the overall shape of the groom and rare shapes, such as a few stray or curly strands, that a random selection tends to miss.
The chosen strands keep their ids, strand channels and surface attachment, so operators placed above work on them like on any other guides.
Parameters
- Guide Count - The number of strands to keep as guides. If the input has fewer eligible strands, all of them are kept.
- Importance - A texture map or strand channel that scales how much each strand's shape matters. Strands with higher values are more likely to get a guide nearby, and strands with a value of 0 are never chosen as guides.
- Random Seed - Changes the initial random strands. The same seed and input always give the same guides.
Using the operator
Add Reduce Guides to the stack above the operator that produces the dense hair, for example Hair from Guides Operator, or above an imported groom. It is found in the Generators category of the Add Operator menu. Choosing a few thousand guides from a hundred thousand strands takes well under a second.
Notes:- When the input hair is animated, the guides are chosen again on every frame, so a deforming input can get different guides on different frames.
- Adopt External Guides binds each hair to the guides with the closest roots. In grooms where very different shapes are mixed together, such as curls among straight hair, a hair can follow a nearby guide of a different shape.