Simulation setup demonstration

There are two ways you can set up physics simulation in Unity Physics. You can use a combination of Unity Physics and PhysX, or just Unity Physics. This page demonstrates how to create a scene that has both a floor, and an object that falls via gravity and lands on the floor. In both cases, the starting steps to create the floor are the same.

Using Built-In Physics Authoring components

First, you need a static body to act as a floor so that your dynamic bodies can hit something and not just fall out of the world:

  1. Create a new SubScene inside the same scene. SubScenes convert Unity GameObjects into Entities.
  2. Create a Cube primitive: GameObject > 3D Object > Cube.
  3. Make the Cube really wide on the X and Z axes – for example: (20,1,20).

Next, create an object that can collide with the floor. Use the first SubScene to proceed with the following steps:

  1. Create a Sphere primitive GameObject (GameObject > 3D Object > Sphere) and place it hovering above the floor.
  2. Add a Rigidbody component. The GameObject needs to fall under simulated gravity, so make sure the Use Gravity property is checked.
Note

For more information, see the PhysX documentation on Rigidbody and Collider components.

Once all of the steps are done, it should look like the following picture:

collider_cast

To simulate, enter Play mode in the Editor. The Sphere should fall and collide with the floor.

For more information refer to the built-in physics authoring section.

Using Custom Unity Physics Authoring components

First, you need a static body to act as a floor so that your dynamic bodies can hit something and not just fall out of the world:

  1. Create a new SubScene inside the same scene. SubScenes convert Unity GameObjects into Entities.
  2. Create a Cube primitive: GameObject > 3D Object > Cube.
  3. Make the Cube really wide on the X and Z axes – for example: (20,1,20).
  4. Remove the Box Collider component. This is the legacy Physics representation, and is not necessary for Unity Physics.
  5. Add a Physics Shape component. The wireframe outline of the collider should match up with the graphical representation.

Next, create an object that can collide with the floor. Use the first SubScene to proceed with the following steps:

  1. Create a Sphere primitive GameObject (GameObject > 3D Object > Sphere) and place it hovering above the floor.
  2. Remove the Sphere Collider component.
  3. Add a Physics Shape component and set its Shape Type to Sphere.
  4. The GameObject needs to fall under simulated gravity, so add a Physics Body component to the object.
  5. Set the Physics Body's Motion Type to Dynamic, and ensure that there is a Mass value (1 will do for this example).

Once all of the steps are done, it should look like the following picture:

collider_cast

To simulate, enter Play mode in the Editor. The Sphere should fall and collide with the floor.

For more information refer to the custom physics authoring section.

Note

The pictures above do not show the default render material.