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LowLevelPhysics2D API workflow

Create a 2D scene with objects that react to physics using the LowLevelPhysics2D API.
Read time 3 minutesLast updated 13 days ago
Create a 2D scene that simulates physics using the 
LowLevelPhysics2D
API.
Follow these steps:
  1. Include the LowLevelPhysics2D library in a C# script.
  2. Create a 2D physics world.
  3. Create physics objects and add them to the world.
  4. Configure objects with definitions.
  5. Attach the script to a GameObject, then enter Play mode.

Include the LowLevelPhysics2D library

In a C# script, add 
using UnityEngine.LowLevelPhysics2D;
at the top to include the 
LowLevelPhysics2D
library.
You can use the 
LowLevelPhysics2D
API in any C# script, not only MonoBehaviour script files. But if you use a MonoBehaviour script file, you can configure physics properties in the
Inspector

?

window of a GameObject, move GameObjects, and attach sprites.

Create a 2D physics world

To add 2D physics objects, you first need to create a 
PhysicsWorld
object to add them to. Do either of the following:
  • Use the world Unity automatically creates.
  • Create a new world.
For more information, refer to Create a physics world.

Create physics objects

To add physics objects to the world, do the following:
  1. Create a 
    PhysicsBody
    object, which defines the position, rotation, and velocity of an object. It doesn't define an area.
  2. Attach one or more 
    PhysicsShape
    objects to the 
    PhysicsBody
    , which define the area that interacts with other shapes. Unity also draws the shapes as a debug visualization.
  3. Add the body to the world you created.
For more information, refer to Create a physics object.

Configure objects with definitions

To configure the properties of the world and its physics objects, create definition objects, for example 
PhysicsBodyDefinition
. Definition objects contain properties like 
position
and 
gravity
that you can adjust in the Unity Editor, or pass into the object when you create it.
To configure the properties in the Inspector window, make the definition object a 
public
field.
For more information, refer to Configure objects using definitions.

Attach the script to a GameObject

To start the simulation, you usually attach the script to a GameObject in your scene, then enter Play mode.
By default, physics objects don't move a GameObject. To make a physics object update the Transform component of the GameObject, refer to Move a GameObject with the LowLevelPhysics2D API.
To add a sprite, refer to Add a sprite to an object.

Example

The following example creates a small circle that falls under gravity onto a large circle. Attach the script to a GameObject in your scene, then enter Play mode.
using UnityEngine;using UnityEngine.LowLevelPhysics2D;public class Example2DPhysics : MonoBehaviour{    void Start()    {        // Create the world        PhysicsWorld world = PhysicsWorld.defaultWorld;        // Create a body in the world, with a definition object that sets the position and enables physics        PhysicsBody object1 = world.CreateBody(new PhysicsBodyDefinition        {             position = new Vector2(0.5f, 8f),            type = PhysicsBody.BodyType.Dynamic        });        // Attach a circle shape to the first body         PhysicsShape object1shape = object1.CreateShape(new CircleGeometry());        // Create a second body in the world, with a definition object that sets the position and disables physics        PhysicsBody object2 = world.CreateBody(new PhysicsBodyDefinition        {             position = new Vector2(0f, 0f),            type = PhysicsBody.BodyType.Static        });        // Attach a circle shape to the second body         object2.CreateShape(new CircleGeometry {             radius = 3f,        });    }}

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