Bendy Shapes and Tails

1What a bendy shape actually is

A bendy part is any long, flexible shape that curves along its length: a tail, a rope, a strand of hair, a tentacle, a scarf. The trick is that it should bend smoothly, like a real rope, not fold at hard hinge points like a robot arm. To get that smooth curl you need two things working together: a shape that can deform, and a chain of bones running down its backbone to steer it. This whole tutorial is about wiring those two things up so the chain carries the shape like a hand carries a ribbon.

2There is no curver layer here

Be clear on this up front. Some desktop animation software has a special bendy-bone or curve layer that turns a bone chain into a smooth spline automatically. FoundryInk does not have that feature, and there is no button to add one. Do not go hunting for it in the panels; you will not find it. Everything you need to get the same result is already here, it just takes a short recipe instead of one dedicated layer. That recipe is the rest of this page.

3Open a vector surface to draw on

Bendy parts start as drawn vector shapes, so you want a surface you can both draw on and rig. In the Animation studio, add a vector layer with the Vector add-row button, or open the drawing surface with Draw and rig. The surface opens with three top modes: Draw, Rig, and Test. You will draw the tail in Draw, build its bones in Rig, and jiggle it in Test to check your work, all without leaving this surface.

4Draw the centre line of the tail

In Draw mode, pick Add Point and click a series of points that trace the backbone of your tail, from the base where it joins the body out to the tip. Six to ten points along the length is plenty; more points means smoother bending but more to manage. Keep the spacing fairly even so the bend looks natural later. Press Esc to finish the line open (you want an open line here, not a closed loop). This centre line is the skeleton of your artwork before any bones exist.

5Round the line so it flows

A tail should curve, not zigzag. Select all the points on your line, then in the contextual Curve group choose Smooth to round the corners into a flowing line. If a spot is too loose or too tight, grab the Curvature tool and drag up to round a point more or down to sharpen it. Aim for a gentle, even sweep, the resting shape of a relaxed tail. This is the pose the bones will start from, so make it a comfortable one.

6Give it width with Line Width

Here is the taper trick, and it is the heart of the look. Rather than drawing two outlines and filling between them, use the outline itself as the body of the tail. In the Fill group pick Line Width and drag along the line to make it thick at the base and thin toward the tip. A fat root tapering to a fine point reads instantly as a tail, a horn, or a brush of hair. You are literally painting the thickness onto the stroke, no second shape required.

7Style the stroke and add a fill if you want one

Open the Shape style panel to colour your tapered stroke. Turn on Enable outline and pick a Line colour, or use a Swatch paint like Oxblood or Amber for a quick pick. If your tail should be a solid colored body rather than just a line, you can also build a closed shape around it and turn on Enable fill with a Fill colour, but for most tails and ropes the tapered stroke alone does the job. Keep it simple; a bendy part reads by its motion more than its detail.

8Switch to Rig and lay the first bone

Now the skeleton. Flip the surface to Rig mode and pick Add Bone. Starting at the base of the tail where it meets the body, drag from the start of the bone to its tip, following your centre line. This first bone is the root of the chain, and it is what you will parent the tail to the body with later. Keep it short enough that the whole tail will take several bones; a good chain has room to curve, and one giant bone cannot curl at all.

9Chain the rest of the bones down the length

With the first bone still selected, drag Add Bone again from its tip to build the next link; because the selected bone becomes the parent, each new bone chains onto the last automatically. Walk your way down the tail, four to eight bones total, ending at the tip. More bones give you a smoother, more controllable curl; fewer bones bend in blockier chunks. Line each bone up along your smoothed centre line so the skeleton and the artwork share the same backbone. When you are done you have a jointed chain running the full length of the shape.

10The key step: Flexi Bind the points to the chain

This is the step that replaces the missing curve layer, so read it twice. With your bone chain built, choose the Flexi Bind bone tool. Flexi Bind tells the drawn points to follow the whole chain smoothly, each point weighted between the nearby bones, so when the bones bend the shape flows around the curve instead of snapping at each joint. Apply it to your tail's points and the shape will now bend like a real rope. This is the difference between a smooth swish and a folding cardboard cutout.

11Bind Points versus Flexi Bind, and when to use each

There are two ways to attach points to bones, and picking the right one matters. Bind Points locks the selected points rigidly to a single bone, so they move as one solid piece, perfect for a stiff paw or a rigid claw at the tail's tip. Flexi Bind spreads each point's influence across the chain for smooth bending, which is what the flexible length of the tail needs. A common pattern is Flexi Bind for the whole bendy body, then Bind Points to nail a small hard detail like a spade tip or a tuft to its own bone.

12Test the bend before you trust it

Flip the surface to Test mode, which lets you drag the bones to preview motion without saving anything. Grab the tip bone and drag it around; the whole tail should curl and follow in a smooth arc. Watch for two problems: hard creases at a joint (usually a hard bind that should be Flexi Bind) and points that get left behind or stretch oddly (a point that missed the bind). Fix anything ugly now, back in Rig mode, while it is cheap. Nothing you do in Test is kept, so drag freely.

13Add Dynamic for natural sway

This is the part that makes the tail move on its own without you keying every wiggle. Select a bone in the chain, open the Bones panel, and tick Dynamic. That turns the bone into a spring: when the body moves, the bone lags and swings and settles by itself, like real weight on the end of a tail. Three sliders shape the feel: Stif (how firmly it springs back), Damp (how quickly the wobble dies down), and Inert (how much it resists starting and stopping). Tick Dynamic down the chain and the whole tail follows the body with a natural delayed swish.

14Tune the spring: Stif, Damp, and Inert

The three Dynamic sliders are worth understanding by feel. Raise Stif for a taut, quick-snapping tail like a stiff cat tail; lower it for a loose, floppy rope. Raise Damp to make the wobble settle fast (a heavy, wet tail); lower it to let it ring on and on (a light, whippy strand). Inert adds weight to the ends, so the tip lags further behind and overshoots more, great for a heavy tuft or a weighted rope end. Nudge one slider at a time and preview, because they interact.

15Parent the tail to the body and finish up

Finally, connect the tail to the rest of the character. Select the tail's root bone, and in the Bones panel set its Parent to the body or hip bone it should hang from. Now when the character moves, the tail travels with the body, and its Dynamic bones add the sway on top automatically. If the tail's root should twist as the body turns, you can also drive it with Angle from a control bone and a Ratio, but for most tails, parenting plus Dynamic is the whole job. Save, and you have a living bendy part.

Bendy shape questions