Clump Operator
The Clump operator gathers groups of hairs together into distinct clumps, the way real hair forms tufts. You control how clumps are generated, where they sit, and how strongly hairs are drawn toward them. Each clump is defined by a central stem, and a new Clump operator generates its clumps right away with Dynamic Clumping, so you can see the effect immediately.
How clumping works
Clumping is computed on the hair currently visible in the viewport. Hairs added later - if you raise the hair count, or at render time - are assigned to clumps by following the hairs that were present when the clumps were generated, which act as clump guides. The closest clump guides decide which clump each final hair belongs to.
A practical consequence: the more hairs are visible while you generate and edit clumps, the more precise the clump borders will be. Changing the viewport hair count after clumping does not disturb existing clumps; it only changes the hair used to update the internal clump guides.
Controlling clumps
You can add, remove, and reposition clumps, and adjust how tightly hairs are attracted toward their stems and how that attraction varies along the strand length. Drive the amount with a strand channel or map for natural variation, and limit the operator to part of a groom with a strand group.
Generating clumps
The Clump Creation Method decides where clumps are placed:
- Even - clump centers are spread evenly across the surface, so clumps come out at a consistent size with no bunching and no bare patches. This is the default.
- Random - clump centers are drawn at random from the existing hairs. Clumps vary in size, and some will sit close together while other areas are left without one.
- Guides - one clump per guide, so the guides decide both where clumps sit and what shape their stems take.
- Strand Groups - one clump per strand group of the incoming hair.
- External Clump Strands - clump stems come from a separate set of strands which you can edit on their own.
Clump Count sets how many clumps the Even and Random methods generate; the other methods take their count from whatever they are generated from. Random Seed rearranges the clumps without changing how many there are.
With the Even method, a Distribution Map controls where clumps are allowed: they concentrate in the light areas of the map and are left out of the black ones. The requested clump count is still reached, so masking off part of the surface packs the clumps more densely into what is left rather than producing fewer of them overall.
Dynamic Clumping
A new Clump operator uses Dynamic Clumping: it generates its clumps itself, and generates them again whenever the incoming hair, the Clump Creation Method or the Dynamic Clumping Clump Count changes, so you never have to create them yourself. Turn Dynamic Clumping off to create clumps only by hand, with the Clump action of the Clump Hairs tool (see Clumping selected hairs).
Clumps you change with the clump tools are kept when Dynamic Clumping generates the clumps again: moving or reshaping a clump, giving it a pattern or an ornament, or overriding its amount or twist makes it your own. Unclump with clumps selected removes them and leaves their hair unclumped, and it stays unclumped.
Your clumps and the places of the deleted clumps count toward the Clump Count, and the generated clumps are placed around them. Hair closest to a deleted clump stays unclumped, and hair closest to one of your clumps joins it. Reset Edits discards your clumps and deletions, so Dynamic Clumping generates all of the clumps again.
Clumping selected hairs
The Clump Hairs tool, the first of the clump tools on the Clump tab of the toolbar, selects hairs rather than clumps, by clicking or with a rectangle, circle or lasso. Its Clumping group then works on the selected hairs:
- Clump (C) - forms Clump Count clumps of the selected hairs, taking them out of the clumps they were in. The hairs are divided into groups lying close together, one group per clump, and the clumps they leave move to the middle of the hairs they keep.
- Unclump (Shift+C) - takes the selected hairs out of their clumps. In the other clump tools it removes the selected clumps.
Each is dimmed while there is nothing for it to act on. Select by Clump (G) also selects the other hairs of the clump of each selected hair, and the Deselect group's Unclumped (Alt+U) and Clumped (Alt+C) drop the selected hairs which are out of clumps or in them. The hairs stay selected while you work in another clump tool. To clump all of the hair by hand, select all of it (Ctrl+A) in the Clump Hairs tool and press Clump.
The clumps you form and the hairs you unclump are kept by Dynamic Clumping like your other edits.
Keeping clumps apart
Clumps which use the Volume shape method can be kept from reaching into each other, so that their hairs do not pass through the neighboring clumps. The Volume Collisions group of the operator's properties is available while the operator's Shape Method is Volume, and its Method chooses how the clumps are kept apart:
- None - clumps may reach into each other. This is the default.
- Preserve Edits - the clumps keep the shapes you give them, and copies of their volumes are pushed apart. A clump pushed aside by a neighbor springs back once the neighbor moves away or narrows again. Clumps you have reshaped with the clump tools give way less than the others.
- Adjust Volumes - the volumes themselves are pushed apart and keep the change. The clump you are changing keeps the shape you give it and pushes aside the clumps it reaches into, which stay pushed even after it moves away. Reset Volume in the Transform Clumps tool discards the changes, and undo takes back the pushes together with your change.
Squash sets how much of each overlap is resolved by narrowing the clumps rather than by moving them apart, from 0 (moving only) to 1 (narrowing only).
Near their roots, where neighboring clumps leave the surface side by side, clumps may still overlap; they are kept apart from where their hairs have left the surface. Clumps packed so tightly that they cannot be separated fully are pushed apart as far as they can move and narrow. When you change some clumps, only the clumps around them are resolved again, so editing stays quick in grooms with hundreds of clumps.
Clumps within clumps
The Fractal group clumps the hair again inside its clumps, so that large clumps break up into smaller sub-clumps, the way wet or styled hair forms locks within locks. Iterations sets how many times the hair is clumped. At 1, the default, the operator clumps once as usual. Each further iteration splits the previous iteration's clumps into smaller ones, and every sub-clump stays within one clump of the iteration before it. This gives the same result as stacking Clump operators, each using the previous one's clump indices as its Region channel, in a single operator. 2 iterations is usually enough, further iterations change little once the clumps are tight.
- Size Reduction - how much smaller each iteration's clumps are than the previous iteration's. Each iteration has 1 / (1 - value)^2 times as many clumps, about 2.8 times at the default 40%.
- Amount Reduction - how much weaker each iteration's clumping is than the previous iteration's. Higher values keep the hair in the larger clumps, and at 100% only the first iteration clumps.
- Goal Feedback - how closely each iteration's sub-clumps follow the previous iteration's clumps. At 100%, the default, they stay inside the larger clumps, which read as single clumps when they are tight. Lower values let the sub-clumps spread apart and replace the larger clumps.
The Clump Index channel and Set Clump Strand Groups describe the clumps of the first iteration.
Accurate Bundling
At full Amount a clump gathers its hairs into a single line. With Accurate Bundling enabled, a clump keeps the thickness its hairs need to lie side by side, which depends on how many hairs it has and on their widths: clumps of many hairs stay thicker than clumps of few. The thickness follows the hair widths along their length, so a clump of hairs that taper, for example with a Change Width Operator before the Clump operator, narrows toward the tips.
- Width Scale - scales the widths that are packed. Higher values make the bundled clumps thicker, and 0 turns the limit off.
- Width - the width used for hair without widths of its own. It is dimmed when the hair has widths.
Accurate Bundling works with both shape methods, for clumps without patterns.
Braided clumps
The shape of a clump can follow a pattern rather than a simple cone. Combined with the Clump operator, braid patterns turn clumps into procedural braids. See Braid Patterns.
Related
- Clump Tools - edit the clumps by hand in the viewport.
- Braid Patterns - procedural braid shapes for clumps.
- Frizz Operator and Curl Operator - add variation within and around clumps.