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Create an object with the LowLevelPhysics2D API

Create a 2D physics body, then attach shapes to the body.
Read time 3 minutesLast updated 12 days ago
Note
This documentation is about writing C# scripts using the 
LowLevelPhysics2D
API. To use 2D physics in the Unity Editor using components like the Rigidbody 2D component, refer to 2D physics instead.
After you create a physics world, you can add physics objects to the world.
An object is usually made up of two parts:
  • A physics body, which defines the position, rotation, and velocity of the object. It doesn't define an area.
  • One or more physics shapes attached to the body, which define the area that interacts with other shapes. Unity also automatically draws the shapes as a debug visualization.
You can add any number of shapes to a physics body. You can create shapes with the following geometries:

Create a physics body and physics shape

Follow these steps:
  1. Create objects that hold the properties of the body and shapes. Make them 
    public
    fields so they display their properties in the
    Inspector

    ?

    window. For example:
    public PhysicsBodyDefinition bodyDefinition = new PhysicsBodyDefinition();public PhysicsShapeDefinition shapeDefinition = new PhysicsShapeDefinition();
    A new definition has a set of default values. For more information about definitions and changing the default values, refer to Configure 2D physics properties using a definition.
    You can also use 
    PhysicsBody.defaultDefinition
    to get a definition object with the default values.
  2. Use the 
    CreateBody
    method of the world object to add a body to the world, and pass in the body definition.
    PhysicsBody myObject = world.CreateBody(bodyDefinition);
  3. Create a shape using a geometry object, for example a 
    CircleGeometry
    object. For example, the following creates a circle with a radius of 2 meters.
    CircleGeometry circleShape = new CircleGeometry { radius = 2f };
  4. Attach the shape to the body using the 
    CreateShape
    method of the body, and pass in the shape definition.
    myObject.CreateShape(circleShape, shapeDefinition);
  5. If your script is in a 
    MonoBehaviour
    class attached to a GameObject, adjust the properties of the body, the geometry, and the shape in the Inspector window.
    To configure the objects in your script instead, set the properties of the definition object before you create the objects. For more information, refer to Configure 2D physics properties using a definition.
  6. Enter Play mode to run the script and create the objects. Unity displays the shape in the Scene view and Game view as a debug visualization. The line on the shape points towards the rotation direction of the shape.
Note
By default, a physics body is static and isn't affected by physics. To make it dynamic, in the Inspector window of the GameObject, set
Body Type

?

to Dynamic. For more information, refer to Configure objects with definitions.
After you create a shape from geometry, the shape doesn't change if you change the geometry object.

Example

The following example creates a circle. Attach the script to a GameObject in your scene then enter Play mode to check the shape.
using UnityEngine;using UnityEngine.LowLevelPhysics2D;public class CreateWorldAndObjects : MonoBehaviour{    // Declare definitions that contain default properties for the body and shape    public PhysicsBodyDefinition bodyDefinition = PhysicsBodyDefinition.defaultDefinition;    public PhysicsShapeDefinition shapeDefinition = PhysicsShapeDefinition.defaultDefinition;     void Start()    {        // Get the default world        PhysicsWorld world = PhysicsWorld.defaultWorld;        // Create the physics body with the body definition        PhysicsBody myObject = world.CreateBody(bodyDefinition);        // Create the circle geometry        CircleGeometry circleGeometry = new CircleGeometry { radius = 1.5f };        // Create the shape with both the geometry and the shape definition        myObject.CreateShape(circleGeometry, shapeDefinition);    }}

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