Cable Design with Grasshopper 3D using Kangaroo

Have you ever wanted to simulate realistic cables that maintain tension and flow naturally between devices or components? In this tutorial, we’ll walk through how to create dynamic, form-found cables in Grasshopper 3D using the Kangaroo physics engine.

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Goal

We want to generate a cable between two anchor lines (Line A and Line B), ensuring:

• Tangency at both ends
• Realistic curvature and slack
• Control over bending, length, and gravity

Components Used

1. Length Line
   Maintains constant cable length
   Helps simulate inextensible cable behavior using a Spring force between points.
2. Rod
   Controls axial stretch and bending strength
   Used to make the cable naturally curve while resisting sharp bends.
3. Anchor
   Fixes the start and end points of the cable
   Anchors are placed at the endpoints of Line A and Line B.
4. Dynamic Weight
   Simulates gravity
   Adds subtle sag and realism to the cable’s shape.
5. Direction
   Maintains tangency at both ends
   Ensures the cable starts and ends aligned with the direction of Line A and B respectively. These are implemented as directional constraints.

Visual Setup

On the left: Rhino viewport shows the final cable hugging the VR headset and strap
On the right: Grasshopper definition using Kangaroo with tunable sliders for fine control

Workflow Overview

1. Define Line A and Line B (your target ends).

2. Import in GRasshopper.

Apply Kangaroo Goals:

• Length (Spring) to simulate fixed cable length.
• Rod for smooth bending.
• Anchor to fix start/end points.
• Direction constraints to control tangents.
• DynamicWeight for gravity effect.

Run simulation with Kangaroo Solver.

Why Use This Setup?

• Avoids manually adjusting control points for aesthetics
• Works for cables, hoses, elastic bands, and even lanyards
• Can export directly to manufacturing-ready geometry

Tip

Tweak the BendStrength and AngleFactor to simulate different cable stiffness — useful when switching from rubbery silicone cables to stiff braided ones.
Flip Curve direction if the cable is drawn the opposite way.

Reference:

https://discourse.mcneel.com/t/bending-rod-circles-splines/84971
‍https://www.youtube.com/watch?v=hKeYG6DJwV0
‍https://discourse.mcneel.com/t/extending-rod-simulation-in-kangaroo/157682
‍https://sketchfab.com/3d-models/apple-vision-pro-3341d1f3f75e41b59fcedd1f46f03d56

Learn More

Want to dive deeper into parametric hardware modeling and cable routing in Rhino/Grasshopper?
Check out our live workshops at Cademy.xyz!