[Unity] How to use the Cloth component to represent cloth movement

This article explains how to use one of Unity’s components, “Cloth”, to represent the mesh of a 3D model as cloth.
We will start with how to use the component and explain the basic usage.
Let’s understand the physical representation and apply it to our VR creation!

Sample

This is a simulation of a Plane with a Cloth component attached colliding with a Sphere.
Let’s see what we can create.

Preparation

Let’s start a Unity project and create a new scene.
In this scene, we will create a Plane to which we will attach the Cloth component and a Sphere that will collide with it.
Right click on the Hierarchy window and select 3DModel > Plane and Sphere to create them.

The Transform of Plane is as follows.

The Sphere Transform should look like this

The scene window should look like the following.

Now we are ready.

Cloth Component

Let’s add a Cloth component to the Plane.
With the Plane selected, select “Cloth” from “Add Component” in the Inspector window to add it.

Now we have added the Cloth component.
Looking at the component, you can adjust various properties.

Properties

Each property and function of the Cloth component is shown below.

Properties	Function
Stretching Stiffness	Sets the stretch rate of the cloth.
Bending Stiffness	Sets the bending stiffness of the cloth.
Use Tethers	Applies a restriction that prevents moving cross particles from moving too far away from fixed particles.
Use Gravity	Applies a gravitational acceleration to the cross.
Damping	Sets the damping factor for the motion.
External Acceleration	Sets a constant external acceleration to the cross.
Random Acceleration	Sets the acceleration to be applied randomly to the cross.
World Velocity Scale	Sets how much the character’s movement in world space will affect the cross vertices.
World Acceleration Scale	Sets how much the character’s acceleration in world space will affect the cross vertices.
Friction	Sets the coefficient of friction of the cross when it collides with the character.
Collision Mass Scale	Sets how much the density of the colliding particles will be increased.
Use Continuous Collision	Allows you to enable continuous collision to improve collision stability.
Use Virtual Particles	Adds one virtual particle per triangle to improve collision stability.
Solver Frequency	Sets the number of solver iterations per second.
Sleep Threshold	Sets the cross sleep threshold.
Capsule Colliders	Sets the array of capsule colliders that the cross instance will collide with.
Sphere Colliders	Sets the array of sphere colliders that the cross instance will collide with.

Properties: Taken from the Unity manual “Cloth”. 
https://docs.unity3d.com/ja/2019.3/Manual/class-Cloth.html

The detailed settings for each item will be adjusted when representing clothing and other items.
We will omit them this time since we are just trying to learn the basic usage.

Colliding a Plane with a Sphere

Let’s try to collide a Plane and a Sphere as a basic usage.
The Cloth component will activate Gravity even without attaching a Rigidbody.

Let’s play the scene in this state.

The Plane and the Sphere do not collide with each other, but pass through each other when played in this state.
Set the properties of the Cloth component to make them collide.

Sphere Colliders

A typical way to make a 3D model with a Cloth component attached collide with another 3D model is to use the Sphere Colliders of the Cloth component. Here is an explanation.

With the Plane selected, check the Cloth component in the Inspector window.
You can set the property “Sphere Colliders” to collide.

Click on the left ▶ to display the menu.
When the menu appears, a property labeled “Size” will appear.
The value of “Size” is the number of Colliders that will be used to set the hit detection for the Cloth component.
Currently, it is set to “0”, which means that the number of colliders that will be set to collide is zero (because the Sphere is not set to collide), so no collision will occur.

Set the Sphere Colliders to the Spheres in the scene.
Set the Size value of the Sphere Colliders to 1.

You will now see a new property called “Element 0”.
There are First and Second properties, but we will only use First.
Drag and drop the Sphere in the Hierarchy window to the empty space in the First property.

The Sphere in the scene is now set to be a hit point for the Plane (Cloth).
Let’s try playing the scene.

The Sphere actually collided with the Cloth, and the Cloth-like movement was expressed.
If you want to create another Sphere and collide it, set the Sphere Colliders of the Cloth component in the same way again.

In addition, “Capsule Colliders” on the properties can be used to set the collision detection for the Capsule Collider in the same way.
Use Capsule Colliders when you want to set the hit detection for people, etc.

Uploading to STYLY

Let’s apply these cloth expressions to create various artworks!
By pursuing the cloth expression, you can simulate real objects such as clothes, flags, etc.
In this article, we’ve only covered the basic usage, but in another article, we’ll be able to create clothes, flags, and more!

Finally, let’s upload the file to STYLY. Finally, let’s upload to STYLY.
This time, let’s upload it as a prefabricated Game Object. When uploading as a prefabricated Game Object, make the Sphere and Plane empty Game Objects, then prefabricate the Game Object and upload it.

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