Binding and weights
Connect a layer's points to your skeleton so the artwork deforms when the bones move.
Artwork can follow a skeleton in two ways. Place a layer inside a bone layer and it follows the bones by itself, with no binding at all: see Automatic following below. Or bind it by hand. Binding connects individual points on a Shape or Mesh layer to one or more bones, each with its own weight, so a hinge like an elbow can hand off smoothly from one bone to the next. Bound points always win over automatic following. See Bones basics for building the skeleton itself.
The Bone Bind Tool does the binding. With Weight Paint off, it lets you pick a bone, select the points that should follow it, and bind or unbind them; turning Weight Paint on switches the same tool to hand-painting influence: see Weight painting.
Automatic following
Drag a Shape, Mesh or Image layer inside a bone layer in the Layers panel, and it follows that rig's bones by itself. A layer nested deeper, in a group inside the bone layer, follows too. Each point moves with the bones near it, blended by each bone's Weight Area. Which bones hold a point is measured on the rest pose, so bending the rig never changes which bones hold it, only where they carry it.
Binding, at the top of the bone layer's Bones section in the Properties panel, chooses how this works for the whole rig:
| Binding | What moves the artwork |
|---|---|
| Flexible | Every bone moves the artwork near it, more strongly the closer it is and the larger its Weight Area. Nearby bones blend smoothly across a joint. A new bone layer starts on Flexible |
| Region | A bone moves only what lies inside its Weight Area. Where areas overlap, they blend. A point outside every area moves with the nearest bone |
| Manual | Nothing follows by itself. Only bound points and linked layers move with the bones. A project saved before this setting existed opens on Manual, so its rigs keep moving exactly what they moved before |
Only Stretched bones take part. A Static handle moves no artwork. A bone whose Weight Area is 0 moves no artwork either, which makes it a control bone. A bone in a branch that a Branch Switch has put away also moves nothing.
What you set by hand keeps priority. A point you bound follows its own bones. A point bound at less than full weight hands the rest of its weight to automatic following, so it no longer lags behind. A layer linked with Link Layer rides its bone rigidly, and a group linked to a bone carries everything inside it as one piece. Layers inside a Mesh layer are moved by the mesh, not by the rig.
Pictures bend as well. An Image layer inside the rig bends with the bones like any other artwork there.
Limiting a layer to some bones
- With the Bone tool, select the bones that should move the layer.
- Select the layer.
- In the Properties panel, under Transform, set Bone Influence to Selected bones. The number in brackets shows how many bones it will take.
The chosen bones are listed by name under the row. To change them, select other bones and choose Selected bones again. All bones goes back to every bone. The choice applies to every selected layer that the same rig moves. Bone Influence only appears for a layer inside a bone layer whose Binding is Flexible or Region.
Selecting a bone and points
Click within a few pixels of a bone to select it, or Shift+click to select several. Shift extends the selection only among bones of the same kind, so Static handles and deforming bones never mix in one selection: the same rule the Bone tool follows. Click a point on any editable Shape or Mesh layer to select it, or Shift+click to add more points to the selection. Dragging over empty space starts a marquee that only picks up points on layers already in your selection, so you can box-select safely without sweeping up a neighbouring shape.
| ShiftJ | Bone Bind Tool |
| Enter | Bind the selected points to the selected bone |
| U | Unbind the selected points from the selected bone |
A bound point defaults to a weight of 1.0 for that bone. Binding the same point to a second bone splits its influence between the two, which is what lets a knee or shoulder bend without a hard crease.
What stable point identity means
Every point on a Shape carries its own permanent identity that survives editing. Insert a point mid-segment, delete another, or reorder the path with the Node tool, and the bindings you already made stay attached to the same points. Celas Studio does not re-count positions and guess. This is what makes it safe to keep refining a drawing after it is rigged.
Auto Weight
Auto Weight replaces the bindings on the shapes you are working with with a smooth, distance-based falloff from every bone in the layer, up to four influencing bones per point. Each bone reaches as far as its Weight Area. Run it with points selected to limit it to the shapes those points belong to. Otherwise it works on the selected layers, and a selected group brings the layers inside it. With only the rig selected, it works on the rig's own artwork: the Shape and Mesh layers inside the Bone layer and the shapes already bound to it. It never reaches other characters or the background, and it replaces whatever weights the shapes in its scope already carry. It is the fastest way to get a plausible starting rig before you refine anything by hand.
The weight area
Weight Area sets how far the selected bone reaches, from 0 to 100000. Set it in the Properties panel or on the Bone Bind tool's bar. It writes no weights by itself and never touches weights you have painted. Auto Weight uses it as that bone's reach the next time you run it, and a Bone layer whose Binding is Flexible or Region uses it as the bone's strength. A new bone starts at 100. At 0, Auto Weight falls back to roughly seven tenths of the average bone length, while Flexible and Region binding give the bone no influence at all. In Edit mode, with the Bone or Bone Bind tool, the selected bone's reach shows as a capsule around it. With several bones selected, a change applies to all of them.
Mirroring weights
Mirror Weights copies the weight of every bound point across to its mirror point on the opposite side of the canvas, matching bones by name: a bone named Arm.L feeds its weights to Arm.R, and vice versa. Name your bones with a matching .L / .R pair before relying on it.
Rigid layer binding
Link Layer, instead of binding individual points, makes a whole layer ride a single bone rigidly, and it takes priority over automatic following: it moves, turns, stretches and squashes with that bone's motion from rest to its current pose, with no per-point falloff at all. Use it for a prop, an eye, or any layer that should move as one solid piece rather than deform. Unlink returns the layer to its own transform.