# Simulate Actor with Gravity Property Using MATLAB

This example shows how to simulate an actor by enabling physics and gravity properties in the Unreal Engine® simulation environment using MATLAB®. You build a ball to bounce from a plane. First, you create a 3D environment with world object using sim3d.World class and build an actor object using sim3d.Actor class. Then, you create a moveable actor and set a view in the scene. Finally, you view the animation in the Simulation 3D Viewer window. To simulate an actor by enabling physics and gravity properties in the Unreal Engine® simulation environment using Simulink®, see Simulate Actor with Gravity Property Using Simulink.

Unreal Engine® defaults to using the physics engine to control actor motion and perform real-time physics calculations when the physics property of an actor is enabled.

### Create 3D Environment

Create a world object.

world = sim3d.World();

### Build Plane and Movable Ball Actor

Build a ball actor using the createShape function and set the Properties of the actor object. Set the Mobility, Gravity, and Physics properties. Then, build a plane actor. Set the PreciseContacts property of the actor for accurate collision of the ball actor with the plane actor. Add the actors to the world.

ball = sim3d.Actor();
ball.createShape('sphere', [0.5 0.5 0.5]);

ball.Mobility = sim3d.utils.MobilityTypes.Movable;
ball.Gravity = true;
ball.Physics = true;
ball.Translation = [0, 0, 5];
ball.Color = [.77 0 .255];

plane = sim3d.Actor();
plane.createShape('plane', [5 5 0.1]);
plane.PreciseContacts = true;

### Set Viewer Window Point of View

If you do not create a viewport, then the point of view is set to 0, 0, 0, and you can use the keyboard shortcuts and mouse controls to navigate in the Simulation 3D Viewer window.

For this example, use the createViewport function to create a viewport with a single field, Main, that contains a sim3d.sensors.MainCamera object.

viewport = createViewport(world);

### Run Animation

Run an animation set for 10 seconds with a sample time of 0.01 seconds.

run(world,0.01,10)

### Delete World

Delete the world object.

delete(world)