Bone basics

A Bone layer holds the skeleton that moves your artwork: how to build one, parent it, pose it, and take it apart again.

A Bone layer is a container for an armature. The bones live on that layer rather than inside the artwork, so one Bone layer can drive every shape, drawing and mesh in a character. Layers you place inside the Bone layer follow its bones by themselves. Layers anywhere else follow only once you bind or link them. See Binding and weights.

Create one with Layer ▸ Bone, or just pick the Bone tool and click on the canvas in Edit mode and Celas Studio adds the layer for you. New bone layers are named Bones 1, Bones 2, and so on.

Drawing a skeleton#

1. Switch to Edit mode with Tab. Bones are built at the rest pose, on frame 0.
2. Pick the Bone tool with J.
3. Drag on empty canvas to draw the first bone. Where you press is the joint, where you release is the tip; a drag shorter than 10 units is discarded.
4. Drag starting on an existing bone to draw a child from the point you pressed. The new bone is parented to the one you started on.
5. Right-click to deselect. The Bone tool has no context menu.

A new bone is 50 units long and gold. Hold Alt over the selected bone, or turn on Move in the Tool Options bar, to reveal the round grips at its two ends and drag them to change its length and direction; its children counter-rotate so their pose is not disturbed.

Parenting bones#

A bone drawn from another bone is already its child, and moving the parent moves the whole subtree. To change parenting later, turn on Reparent in the Tool Options bar and drag the bone onto its new parent. A drop that would make a loop is refused.

Re-parenting rebases the bone: its rest angle, its posed angle, every angle keyframe on it and the dial of any action it drives are all shifted by the change in parent angle, so the rig does not jump and the action keeps driving.

Move, Reparent and Snap are mutually exclusive: turning one on clears the others. In Move mode, dragging a bone at frame 0 moves its rest position along with all of its descendants; from frame 1 onward it moves the posed position and keys it.

Bone types#

The type pill appears in the Tool Options bar in Edit mode only. With Static chosen, a single click on empty canvas places a handle there rather than starting a drag. A Static bone's pose is its position, so its Position keys are its whole animation. The Bones list says what kind each bone is on a dark chip beside its name: a target for a handle, a bone for a stretched one.

Multi-selection never mixes the two kinds: Shift+click and Ctrl+click only extend a selection among bones of the same type.

Changing a bone's type later#

Bone Type in the Properties panel converts a bone that already exists, and the conversion is non-destructive in both directions. No keyframes are deleted either way: a stretched bone's angle and stretch keys survive a trip through Static, and the position keys a Static handle carried survive the trip back.

Going to Static, the position keys are kept: a handle stores where it sits IN ITS PARENT, so the handle appears exactly where the bone was and the shape, timing and easing of the motion are untouched. That holds for a child bone too, which used to jump somewhere else. Nothing is keyframed for you either, so a bone you set to Static gains no key it did not ask for, and a project saved by an older build is converted as it loads. Converting back and then forward again returns the bone precisely where it started.

A Static handle travels with the bone it is parented to instead of staying behind while its parent animates, and its position keys honour their Keyframe Interval the same way every other channel does, so a sample-and-hold handle steps rather than slides. Hold Ctrl while dragging one to snap it onto a bone's pivot, the way drawing a bone already snaps.

The rest pose and Animate mode#

Edit mode, on frame 0, holds the rest pose: the shape of the skeleton itself. Rotating a bone here rewrites its rest angle and counter-rotates its direct children, so you can rebuild a limb without disturbing poses you have already animated.

In Animate mode, from frame 1 onward, the same drag poses the bone instead: rotation writes the animated angle and keys it. A selected bone also shows a small square handle about four fifths of the way along it; drag that to stretch the bone between 0.05 and 8 times its rest length.

Naming, colour and titles#

Select a bone (in the viewport, or in the Bones list at the top of the Properties panel) to reach its own controls. The name field commits on Enter, and the square beside it sets the bone's colour. Show Title draws that name next to the bone on the canvas, which is worth turning on once a rig has more than a handful of bones. It works the same way on both kinds: the label hangs just under the stretched bone's joint, or just under the Static handle's disc, in the bone's own colour. Shy, just below it, marks a bone to hide with View ▸ Hide Shy Bones: see Shy bones below.

Angle and Stretch carry keyframe diamonds. Length, 1 to 1000, is rest geometry and is not keyframeable. The list header reads Bones: N, and below it Parent and Bindings tell you what a bone hangs from and how many points it holds.

With several bones selected, a change to the selected bone is broadcast only for the fields you actually touched: constraints, IK, Lock, control bones, dynamics, weight area, colour, Show Title and Shy. Names, geometry, keyframes and actions always stay per bone.

Branch Switch#

A Branch Switch turns a bone's child branches into alternatives, with one of them in use at a time: an arm drawn in front of the body and the same arm drawn behind it, for example. Each child bone of the switch starts a branch, with every bone under it. Static handles do not count as branches.

1. Select the bone the branches grow from. It needs at least two Stretched child bones.
2. In the Properties panel, under Branch Switch, turn on Switch Child Branches.
3. Pick the branch in use from Active Branch. The list names each branch by its first bone.

The branches not in use leave the canvas: their bones are not drawn, cannot be clicked and move no artwork. Artwork that belongs only to a hidden branch hides with it: a layer linked to one of its bones, a layer whose points are bound only to its bones, or a layer whose Bone Influence is limited to its bones. The Layers panel shows such a layer dimmed, and its eye stays on.

The branch in use can be animated. In Animate mode, picking a branch always keys it at the current frame, whatever the auto-key channels say, and the change snaps on that frame rather than blending. Active Branch has a keyframe diamond, and the bone's group on the Timeline gains a Branch Switch group holding its row. While you pose, the Bone tool's bar offers the same Branch Switch checkbox and branch list for the selected bone, so you can flip branches without going to the Properties panel.

Shy bones#

Turn on Shy for a bone in the Properties panel, then choose View ▸ Hide Shy Bones (Ctrl+Shift+B) to take every shy bone off the canvas. Hidden shy bones cannot be clicked either, but the rig keeps working: they still move their artwork and their keys still play. It keeps a finished rig uncluttered while you animate its main controls. Choose the command again to bring them back. Shy is not keyframed, and the Hide Shy Bones setting is remembered between sessions.

Deleting a bone#

With the Bone tool in Edit mode, select one or more bones and press Delete or Backspace. Delete Bone at the foot of the Bones section does the same thing to the whole selection.

Deleting a bone never deletes its children. Each child is promoted to the deleted bone's parent with its rest and animated angles shifted so nothing moves, and every reference to the removed bone is repaired: IK targets and control-bone links that pointed at it are cleared, rigid layer links unlink, actions it drove are removed, and a promoted bone's action dial is rebased so its own actions keep working.