Connectors and sliders

A connector is a line between two joints of a figure, with a slider that can travel along it. Anything attached to the slider rides along: a carriage on a rail, the sleeve of a piston, a bead on a string, a zip on a jacket.

The problem it solves

Ordinary parts only hang from one joint. That makes some motions very hard: a piston rod has to stay between the crank and the cylinder, a carriage has to stay on its rail. You would have to fix their position by hand on every frame. A connector is pinned at both ends, so it follows both joints by itself, and its slider gives you one number (Position) to animate.

A 30-second example

1. In the playground, drag the red diamond (the slider) along the blue connector. The green carriage rides with it, and Position in Properties follows.
2. Drag the red joint at the end of the right-hand grey bone (Anchor B). The connector stays attached to both ends, and the carriage stays at the same percentage.
3. Click the connector, then Segment in Properties, and set Bend to 60. The slider now travels along the curve.

Create a connector

You need one figure with two joints in different places. (To attach two separate figures, use Join instead.)

1. Open the figure in Build. Finish its shape first: set the origin and split parts before you add rig rules.
2. Click the first joint. In Properties, open Rig and click Connect. (With nothing selected, the figure’s quick action Connect starts from the origin.)
3. The stage header says Click the second joint to connect it. Click it. Esc cancels.
4. The connector appears, selected, with its slider at 50% and a 6 px line. The app says Connector added. Drag its middle joint to slide.
5. With the slider selected, draw the parts that should ride on it: they hang from the slider joint.
6. Check it with Test rig: drag the slider, then move the anchor bones.

Tip: if you select exactly two parts first, Connect joins them straight away.

Position

Drag the slider on the stage, or type Slider → Position. On a bent connector, 50% means halfway along the curve. Position is part of the pose, so each frame (and each copy of the figure) can have its own.

Segment and Slider

A connector is two things: the line you see (Segment) and the joint that travels on it (Slider). Click the line to select the Segment, the slider to select the Slider, or switch with Segment │ Slider at the top of Properties.

A connector has no Angle or Length of its own: its two anchors decide them. The dashed lines marked A and B appear while the slider is selected; they are only guides and don’t show in your export.

Change the anchors

1. Select the connector and switch to Segment.
2. In Rig → Anchors, click the pick button next to Anchor A or Anchor B. The stage header says Click the new anchor on this figure.
3. Click the joint. The origin can be an anchor too. A and B must be different joints.

Parts attached to the slider turn with the connector. To keep one at its drawn angle instead, set its Attachment → Orientation to Keep authored angle.

Make the connector a stretch driver

In Segment → Rig, turn on Smart Stretch, then choose what drives it in Driven by:

Rest slide goes from 0.01% to 100%. Bending a connector does not change its anchor distance: that is measured in a straight line. Minimum and Maximum only limit how much the attached parts stretch; they never pull the connector off its anchors. More in Smart Stretch.

Animate with a connector

For a piston, turn the crank bone and let the connector keep the rod attached; animate Position only if the sleeve should travel. For a carriage on a rail, keep the anchors still and animate Position from 0% to 100%. Anchors and rules belong to the figure’s design (every copy shares them); Position belongs to the pose. Save figures as .stkz and projects as .styk to keep connectors.

Troubleshooting and limits

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