Manual 14 bones and rigging

Bones and rigging

A rig is a skeleton under your drawing: bones you pose instead of redrawing a limb from scratch. Lightbox's rig is different from the puppet tools' in one way that matters — a posed line is re-drawn along its bent path, not warped like a picture on a rubber sheet, so line weight and brush character survive any pose. And because every dab's scatter and jitter are seeded from the drawing's rest position, a rigged character does not boil as it moves.

A document that never rigs pays nothing: no keys in the file, no rig controls in the way.

The Bone tool

Its panel in Tool options carries everything the tool can do, starting with one switch of three positions — Bind, Pose, Weights. That switch is how you get to weight painting; the three are exclusive — a Weights drag paints influence, it never turns a bone.

Below the switch, the panel lists every bone in the rig, children indented under their parents. Picking one there selects it on the canvas — the same selection a click on the canvas makes — and the selected bone draws white, the same colour selection wears on every overlay. Every bone and handle sits on a dark rim, so the chrome reads on white paper and dark canvases alike.

The rest of the skeleton tells you which of the two things you are looking at. In Bind it is green — that is the rig itself, and a drag there rebinds the drawing. In Pose and Weights it is violet — that is the rig standing at the playhead, and a drag there keys a pose. The two gestures look identical and mean opposite things, so the colour is what separates them without reading the switch. The rest of the panel is what you can do to the picked bone (rename, length, add child, delete, IK, spline, constraints), the weight brush while it is armed, and the binding actions. The pointer says what a press would do before you make it — a move cursor over a bone you can shift, a turn cursor where a drag would rotate it, and a crosshair on empty canvas where a drag would start a new bone.

The Bone tool (K) is always in the toolbar, even before a rig exists — because its first drag is what creates the rig.

• Drag on empty canvas to add a bone, from where you press to where you release. If a bone is selected, the new one is its child; the joint follows the parent from then on.
• Click a bone to select it. Tips beat origins, and the selected bone wins a contested press, so you can work a joint without the neighbour stealing it.
• Drag a bone's shaft to move it bodily — children come with it. Drag a tip to re-aim and re-length it; drag an origin to move just that joint. All three edit the skeleton's rest, and each is one undo step.
• Shift-drag a bone's tip to grow a child out of it, glued to the parent's tip — the fastest way to build a limb, one bone at a time. Glued means the joint follows: re-length the upper arm and the forearm comes with it instead of leaving a gap. Dragging the child's own origin away unglues it again, and it stays where you put it from then on. Add child in the options panel does the same without aiming, and Length sets a bone's size by number instead of by drag.
• A dashed line tethers every separated joint to its parent's tip, so hierarchy stays visible when bones stand apart: a glued joint reads as touching, a parented-but-offset one reads as tethered, and a bone with no line to anywhere is a root. The tether follows live while you drag, and it answers what you are looking at — a glued joint keyed apart by a pose translation shows the tether too, because right now it is apart.
• Rename a bone in the options panel — a pair ending .l and .r is what X-symmetry reads. Delete (the button, or the Delete key while the Bone tool is in hand) removes it and re-parents its children to its parent, leaving them exactly where they are; strokes bound to it lose that binding.

Every one of these drags shows its result while you drag. The bone you are creating, moving, re-aiming or extruding follows the pointer, computed by the same code the release runs — so where the drag shows it is where letting go puts it, and the whole gesture is still a single undo step.

More than one character on a drawing

A drawing can carry several skeletons, and they are all real: each one poses, each one animates on the timeline, and drawings can be bound to any of them. That is what lets you put a second character in as a reference you can pose — rough out where the dog is standing frame by frame and draw over it — without the reference being a dead outline you have to keep re-imagining.

One of them is in hand. The bone tool edits that one: drawing a bone adds to it, and rename, delete and the options rows all mean it. The others draw dimmer, so which is in hand reads without clicking anything, and they have no grab handles.

Click another character to take it in hand. The first click selects it and does nothing else; a second click moves the bone you clicked. Two clicks rather than one, deliberately: the other characters are standing on the drawing you are making, and a stray drag there is expensive. When a drawing has more than one skeleton the tool options also list them, so you can switch without hunting for a bone.

The list of characters is absent when there is only one — a picker over a single rig can only tell you what you already know, and the canvas says it anyway.

Skeleton sets — the same character on the next drawing

A skeleton you built once is worth keeping: the human, the dog, the goblin. Skeleton → Skeleton sets… names the open drawing's armature and puts it in the project, the way a guide set keeps guides. Skeleton → Add skeleton from set puts one back on a drawing. Share a set onto a folder from the project manager, and only the characters that belong to a folder are offered under it.

A set travels in head units, and that is the point. When you save one, its height is measured against the character height scale on that drawing — so the human is 7.5 heads, the goblin 4.5, the dog 3. Put one on another drawing and it is scaled to that drawing's height scale and stood on its ground line, at the same head count. The goblin stays shorter than the human on any paper at any resolution, and nobody has to work out a percentage.

The menu says which is which: Goblin — 4.5 heads beside Human — 7.5 heads.

Three sizes to land at, chosen once under the same menu and used by every pull after it:

By head count	The default, and the reason to keep a library. Needs a character height scale on the drawing you are putting it on
To this canvas	The same share of the height it filled when it was saved — the guide-set rule, and what happens anyway if there is no height scale to measure
The size it was saved	Untouched. Keep this for a size comparison: the goblin being short is the drawing, not a mistake to correct

Save the height scale first. A skeleton saved on a drawing with no character height scale has no head count — nothing measured it — so it can only ever be scaled by canvas share. The editor says so before you save rather than after.

You cannot swap the skeleton under work that is already attached to it. Once a layer follows the rig, or strokes are bound to it, Add skeleton from set is refused: the bind pose is what every mark's grain is computed from, so replacing it would re-roll the lot and the character would come back boiling. Unbind, or start the new character on a new drawing. The same applies to a skeleton you have already posed — the keys name bones that would be gone.

Posing

Switch to posing (Shift+K) and the same drags edit the pose instead of the skeleton. Which part of the bone you take hold of decides what the drag does, and it means the same thing in both modes:

Grab	Posing	Binding
The tip handle	aims the bone	aims it, and sets its length
The shaft	carries the bone, and everything parented to it	moves it in the skeleton
The joint handle	puts the joint under the pointer	moves the rest joint

So take a root bone by its shaft to move the whole character — children ride their parent, so one drag carries the skeleton. The pointer says which of the two you are about to get before you press: a move cursor on the shaft and the joint, a turn cursor on the tip.

The pose is keyed at the playhead automatically — pose the arm on frame 8 and a pose key lands on frame 8, interpolating from and to the keys either side, with the frames between showing the blend.

You can see those keys, on the timeline. Once a document has an armature, the track timeline grows an Armature row marking every frame any bone is keyed on — the camera's row, one track down. Tick Bones on the timeline bar (or click the row's chevron) to open it into one row per bone; it is closed by default, because a twenty-bone character would otherwise cost twenty rows.

The bone rows are the hierarchy, and they fold. Children indent under their parents, and a bone with children carries its own chevron in the gutter — click it and the subtree folds away, so a twenty-bone character can show the one limb you are timing rather than twenty rows or none. Folding is a view's memory, never the document's: a folded bone's keys still play, still export, and still move with the summary row.

The keys are editable where they are drawn:

• Drag a key to retime it. On the Armature row that moves the whole pose; on a bone's row it moves only that bone, leaving its neighbours where they are. A key dropped on top of another replaces it.
• Right-click a key to remove it, copy or cut it (the key clipboard — see Copying keys in the timeline chapter), or jump the playhead to it. On a bone's row, removing takes that bone off the key and leaves the rest of the pose alone; when the last bone comes off a key, the key goes with it.
• Select a bone's key and its X, Y and rotation appear as numbers on the strip under the tracks — the departure from rest the key holds, typed instead of dragged.

A bone that gains a key where there was none is seeded from the pose you were already looking at, so keying one bone never snaps its neighbours back to rest. Scrub the timeline and bound drawings follow the pose live, in playback and in every export.

Timing the rig on 2s

Tweened bones move every frame, and every frame is exactly what drawn animation does not do. Two controls give the rig drawn timing, and both are off until you ask:

• Hold a key. Right-click a pose key ▸ Ease into next ▸ Hold and the pose freezes until the next key — pose-to-pose instead of a tween, the same ease menu the camera's keys have. The other choices (linear, ease in, out, in-out) shape the tween the way they always did.
• Sample the whole track on 2s. Right-click the Armature row's empty run ▸ Pose on… ▸ 2s (or 3s, 4s) and the rig is shown every second frame and held between, while the tween underneath stays fluid. Retiming is the point: change the interval, or a key, and the motion re-samples — nothing is re-posed. Back to 1s (every frame) and the track is exactly what it was.

The step is what the frames show — playback, export and bake all step — while posing keeps working at full precision: a key you add or drag is measured against the fluid tween, on whatever frame the playhead is on. Pose on the sampled frames (the even ones, on 2s) to see your key exactly as the frame will show it. Held poses land on the exposure sheet's grid, so a rig on 2s sits flush with drawings on 2s — and baking a stepped rig writes the held drawings, ready to re-expose and re-time like any others.

The skeleton has its own onion skin. With onion skin on, posing also shows outline ghosts of the skeleton at the neighbouring pose keys — warm behind the playhead, cool ahead, the same colours the drawing's ghosts wear — so an inbetween pose is judged against where it came from and where it goes. The onion bar's switch and depths drive it, and a ghost is never grabbed: a press through one lands on the real skeleton or the canvas.

Press play and the bones get out of the way. Watching a cycle is watching the drawings, and a skeleton drawn over them is chrome you did not ask for — so the rig hides for the length of playback and comes back when you stop. Nothing about the pose changes; only whether it is drawn.

If you would rather watch the rig move, tick Show the bones while the animation plays in Configure ▸ Timeline. It is off by default because the common case — flipping a cycle to judge the timing — wants the drawings and nothing over them. With it on, the bones re-solve at each frame and move with the drawings; with it off there is nothing on screen to go stale. What there is no longer is the third thing, which is what this fixed: the rig frozen at the last pose you touched while everything under it animated.

The rig's onion ghosts stand down for playback either way, the same as the drawing's do — they exist to show where a pose came from and where it goes, which is what you are watching.

The drawing follows the drag, not just the bones. Bound strokes re-render through the provisional pose as you drag, exactly — the same render the release lands, so nothing settles or shifts on pen-up. The one exception is a stroke whose brush carries the expensive badge (a simulated medium, smudge or blur, layer sampling): it draws as a thin ghost of its own centreline during the drag and lands exactly when you release. Nothing is keyed until you let go — and a drag the window loses (focus stolen mid-gesture) is abandoned, the drawing snapping back to its keyed pose.

A pose never touches your lines. It decides where they are drawn; the record keeps them at rest, so un-keying a pose returns exactly the drawing you made.

Baking writes the pose into the drawing: bound strokes become ordinary posed strokes, cut loose from the rig. What you bake is what you saw — the live view and the baked result are pixel-identical.

Keeping a pose as a drawing

Posing writes a pose key and nothing else. That is what makes trying a pose free — but on a long exposure it means the frames you posed still show the one drawing the cel is holding, and playback shows the drawings you made rather than the poses you authored.

Drawing from pose is the other half. Park on a held frame, pose the rig, and use it: the hold breaks and that frame becomes a drawing of its own, holding what you were looking at. Three ways to reach it, all the same command:

• the bone options, which acts on the frame you are standing on;

• right-click a cel in the X-sheet, which acts on the cel you clicked and then takes you to it — the way to work along a row without moving the playhead first. It only appears once the document has an armature;

• a key of your own, bound under Keep this pose as a drawing — worth doing for a cycle, where you press it once per drawing.

• Bound art arrives baked into its posed position, ready to touch up.

• A bone guide over hand-drawn art — nothing bound — arrives as a copy of the drawing the cel was holding, with the posed skeleton showing through it to redraw over. This is the frame-by-frame way to use bones: block the action out with the skeleton, then commit one drawing per frame you want.

Only the frame you are on becomes a drawing. The frames after it go on showing the drawing they were showing — the cel after the new one re-exposes it, so a long hold you commit one frame out of keeps running exactly as it read, and the frames that were following the rig go on following it. Press it on a frame that already has a drawing of its own and nothing is inserted — it bakes the pose into that drawing instead, which is what Bake pose does.

IK — reaching instead of turning

Turning a shoulder and then an elbow to put a hand somewhere is arithmetic an artist should not have to do. IK inverts it: you place the hand and the arm works out its own angles.

Select the bone at the end of the limb and press Add IK. That makes the whole thing in one go — a handle, drawn amber so it is not mistaken for a bone, sitting at the limb's tip. Switch to Pose, drag the handle, and the limb reaches after it. The handle is an ordinary bone, so it keys on the playhead like everything else, and parenting it to a prop or a ground bone is how a foot stays planted or a hand stays on a sword.

• IK bones is how far up the limb the reach goes. Two is an arm or a leg; more is a tail or a neck.
• Pole picks a bone that says which way the elbow or knee bends. Without one the limb keeps whichever way it is already bent, which is usually what you want and occasionally is not.
• Dragging any bone of the limb in Pose moves the handle, because the limb's angles belong to the solver — you are always really moving the hand.
• Remove IK deletes the chain and its handle. The bones stay exactly where they are and go back to being turned by hand.
• Out of reach, the limb points straight at the handle and stops — it stretches no further than it is long.

IK is posing, never the rest: switch back to Bind and the skeleton is the one you built, so re-lengthening a bone under a chain does what you asked rather than being pulled back by the solver.

Constraints — one bone following another

A constraint makes a bone follow another bone, so you pose one thing and several move. Eyes that track a target, a head that looks where a hand goes, a prop that stays in a fist.

Select the bone that should follow, and pick what it follows from constrain to…. That makes it in one go — an aim, because an aim reads instantly: the bone visibly turns to look. Then set what kind of following it actually is:

• Aim at — turn to point at the target.
• Copy turn of — take the target's angle, wherever it is.
• Copy place of — sit where the target sits, keeping your own angle.

Stack Copy turn and Copy place on the same bone and it follows the target completely. There is no tick-box constraint that does everything, because most of the combinations are never used and every one of them would sit in your file at off.

• Offset is degrees added after the constraint resolves — a head that should look slightly past what it aims at.
• Strength is how far toward the constrained result the bone goes. At 100% the constraint owns the bone's turn, so posing it by hand does nothing; lower it and your pose and the constraint blend. At 0% the bone is exactly where you put it.
• Constraints resolve top to bottom, after IK. A later one sees what an earlier one did, and a constraint can override a bone the IK solver just placed.
• A bone cannot follow itself or anything hanging off it — there would be no answer — so those bones are simply not in the list.
• Like IK, constraints are posing. Switch to Bind and the skeleton is the one you built.

Spline chains — tails, hair and capes

Some things are not posed joint by joint. A tail, a plait, a cape, an antenna: what you want is a shape, and the bones should follow it.

Select the bone at the end of the run and press Add spline. Three amber handles appear along it, laid on the shape you already drew — so nothing moves until you move something. Switch to Pose and drag a handle; the run curves to follow.

• Spline bones is how many bones up from the end lie on the curve.
• The curve passes through every handle, not near it. Where you put a handle is where the tail goes.
• Every bone keeps its own length. A spline bends the run; it never stretches it, so the drawing bound to it is never scaled and its grain never re-rolls.
• If the run is longer than the curve, the rest of it trails straight on rather than bunching up at the end.
• Dragging any bone of the run moves the nearest handle, because the run's angles belong to the curve.
• Remove spline deletes the curve and its handles, unless something else is using one.

A tail that whips is three handles keyed over four frames — the handles are ordinary bones, so they key, parent and drag like everything else in the rig.

Joint fixes — drawing the shape a bend should have

Bend a joint far enough and the skinning goes wrong: the inside of the elbow collapses, the outside pinches. That is not a weights problem — the correct shape at 120° is not a blend of anything — so you draw it.

Bend the joint to where it looks wrong. Select the bone, and in Joint fixes press Draw a fix here. The drawing changes to its posed self, and every tool works on it normally: move points, reshape lines, whatever fixes it. Then press Keep the fix.

From then on, the fix eases in as that joint approaches that angle, and holds past it. At rest the drawing is exactly as you made it.

• Bend further and draw again for a second stop; the shape ramps between them. Drawing at an angle you have already used replaces that stop.
• The second capture starts from the first fix already applied, so you are always correcting what you can see.
• Discard puts the drawing back and keeps nothing. Leaving Pose mode does the same.
• Your lines are never changed. A fix decides where marks are drawn, the same way a pose does, so removing it returns the drawing untouched.
• Add or delete lines during a capture and those lines are skipped — the fix can only describe lines that were there when it started.

A fix belongs to the drawing, so it works for the cutout way of animating, where a limb is one drawing you reuse across the whole sequence. It is not a tool for correcting two hundred hand-drawn frames.

Jiggle — secondary motion

Some motion nobody should have to key: the tip of a tail arriving late, ears that carry on after the head stops, an antenna that will not sit still. Tick Jiggle on a bone and it follows the motion driving it through a spring — lagging behind, swinging past, settling.

• Catch up is how hard the bone is pulled toward where the pose wants it. Low is a whippy antenna; high follows almost immediately.
• Settle is how quickly the swing dies. Low keeps it bouncing; high is a heavy tail that lands at once.
• The swing is computed from the pose track, one step per frame — never from the clock — so the same document renders the same swing on every machine, every export, forever. Scrubbing backwards replays it exactly.
• Children ride the swing, so one jiggled bone at the base of a chain moves everything after it. Jiggle belongs on bones you turn by hand — a bone driven by IK, a spline or a constraint gets its swing overwritten by the solver, the same way hand-posing one does nothing.
• Keys never record the swing: what you author is the pose, and the jiggle is how the frames between and after breathe. Baking writes what you see, swing included.

Binding drawings to bones

A stroke follows the rig once it has weights — how much each bone moves each part of it.

• A whole layer at once — right-click the layer and pick Follows the rig. That covers every stroke on it, on every frame, including ones you draw later, and it is what you want for a character you are about to animate rather than a single illustration. Link the character's layers (lines, colour, details) and rigging one rigs them all — see Layers. Nothing is written onto your lines: the layer's binding is read when the drawing is drawn, so linking a layer moves the drawings that were already on it.

• Assign to bone: select strokes, and assign them wholly to the selected bone. This is the cutout workflow — each body part follows one bone — and it covers most rigs.

• Auto-bind: weight the selected strokes against the whole skeleton, by joint. Each part of a line follows the bone it is on rigidly and blends with the neighbouring bone only near where the two meet — so a straight line along an arm stays straight when the forearm turns, and bends at the elbow. It gets a character most of the way; the last stretch — armpits, hips, anywhere two bones share one drawing — is what the heat view and the weight brush are for. Every point's weights add up to the whole, so a drawing keeps up with the rig however far it moves. A line drawn with the line tool is given the extra points it needs where a joint crosses it, so it bends at the joint too; freehand lines already have them.

• Joint (in the Bone tool's options, for a bone with a parent) sets how far either side of that joint a drawing blends, in pixels. The default is a quarter of the shorter of the two bones — 25 px where a 100 px upper arm meets a 100 px forearm. Wider reads softer and rubbery, 0 is a hinge with no blend at all, and Reset goes back to the default. It applies when weights are made: to the next Auto-bind, and at once to a layer that follows the whole skeleton. Strokes already bound keep the weights they were given — select them and Auto-bind again to take a new zone.

• Rigs made before joint weighting keep posing as they did. Strokes that were auto-bound earlier keep their weights, and a layer bound to the whole skeleton earlier keeps the softer distance weighting it was made with, where every bone pulls a little on every line. Choose Follows the rig → The whole skeleton on that layer again to move it to joint weighting.

• The heat view shows the selected bone's influence over the current drawing, blue (none) through red (owned), while the weight brush is armed — in Bind and Pose the ink stays clean. The dots sit on the drawing as it is posed at the playhead, so what you see is what you would paint.

• The weight brush (Ctrl+Shift+K while the Bone tool is active) paints influence for the selected bone directly on the canvas: pressure drives strength (a mouse paints at full strength, like every brush), weights normalise themselves (painting one bone up takes the others down, a locked bone holds), and a whole brush stroke is one undo step. Red means the selected bone owns those points — it is not a warning colour. To exclude a region from moving, do the opposite of painting it red: select the bone that currently owns it and paint there with Subtract. What no bone claims holds still at rest. The brush ring wears a + or − beside it saying which way the next stroke will paint, and the modes have their own keys: Shift+1 arms Add, Shift+2 Subtract, Shift+3 Smooth — from any tool, in one press. The ring is the weight brush's own radius, whatever the paint brush is set to. Points painted part-way (purple, between blue and red) land between their rest and posed positions, which is also the answer to a line that seems to twist in depth as a bone turns: push its weights to fully red or fully blue and it moves rigidly or not at all. With X-symmetry on, painting one side of a named pair (hip.l / hip.r) paints the other side too, mirrored across the pair's own axis — the character's spine, wherever it sits on the paper, and the mirrored dab lands on the other limb wherever its own pose put it. You can paint at any frame: the brush works on the drawing you are looking at — pose the arm to where the armpit goes wrong, and fix the weights right there. The weights themselves are still stored against the rest drawing, so nothing about a pose changes what a weight means. While the brush is armed, nothing moves: the dots change colour dab by dab, and the drawing holds still — painting edits how much a bone influences a line, it never pushes the line around under your hand. The drawing takes up its corrected deformation the moment you switch back to Bind or Pose.

Exporting the rig: the Godot export writes a Skeleton2D importer beside the sheet when the document is rigged, and the Rig + DragonBones format exports the skeleton file for engines with a DragonBones importer — see Exporting to a game engine. All six phases of docs/DESIGN-bones.md are built.