How to create a swinging rope in Unity

I've been prototyping a helicopter game. The helicopter has a winch so it can winch people up from a stormy sea. It took a while to figure out how to make a realistic rope in Unity with C# code, so this is a summary of what I learned.

Image of a helicopter with a winch

Introduction to ropes in computer games

How are you making a rope in a computer game? The most common answer to the question is: you approximate the rope with springs. This may first sound a crazy idea because we don't want a rubber band but a rope and a rope is not bouncy. But the truth is that all materials can be approximated with springs. When the famous entrepreneur Elon Musk first wanted to learn how to design rockets, he read the book Structures: Or why things don't fall down. It says:

The idea that most materials and structures, not only machinery and bridges and buildings but also trees and animals and rocks and mountains and the world itself, behave very much like springs may seem simple enough - perhaps blindingly obvious - but, from [Hooke's] diary, it is clear that to get thus far cost Hooke great mental effort and many doubts. It is perhaps one of the greatest intellectual achievements of history.

So if you know how to make a rope, you will also know how to make cloth. To make cloth, you just add more springs in other directions. This is also how Pixar is simulating hair in their animated movies: by approximating hair with springs.

You will here learn two ways to make a rope:

  1. A realistic rope. This rope will behave like a real rope would.
  2. A simplified rope. This rope will try to overcome the difficulties you will encounter when you make a realistic rope and it will work in most cases. This rope will also be able to move up and down as if attached to a winch.
  3. Another simplified rope. This rope is another solution to the rope problem.

Read more

I don't like to copy what already exists on the Internet, so my tutorials are mostly focused on code with comments. But if you want to read more about ropes, I think these resources were good:


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