Add components to 3D GameObjects

Components add behaviors and functionality to a GameObject. You have used the Transform Component — and that is just the beginning! In this tutorial, you will add another component, the RigidBody Component, which gives a GameObject physical properties so that it can interact with gravity and other GameObjects. You will also position the Main Camera to watch how a GameObject responds to gravity in 3D.

1. Create a new Sphere GameObject in the Hierarchy.

2. Move the sphere to the space inside the Monument, so that it is positioned in “mid-air” above the steps. You can use the Transform tools, the Transform Component in the Inspector, or both.

In every new Scene, there is a camera like the one shown below.

This camera, named Main Camera in the Hierarchy, captures and displays your Scene to the player as it appears in the Game view. While the Scene view is where you build Scenes, the Game view is a preview of the way your game appears to the player.

The camera in your Scene is a GameObject like any other. When you select it, you will see its Transform Component in the Inspector window. You can change these settings as you would with any other GameObject. Note that scaling a camera will have no effect.

When you select a camera, you see the outlines of a pyramid-like shape called the frustum. The frustum shows you what part of your Scene the camera is viewing. Anything outside the frustum is not visible to the camera.

When a camera is selected (1), you can expand the Camera Component in the Inspector (2) to open a Camera Preview window (3) that shows you what is visible to the camera in the Scene.

Move the camera to a position where it can “see” the ball and the steps below it.

Tip: You can also move the camera to align with your current scene view by selecting it in the Hierarchy window and then pressing Ctrl+Shift+F.

Select the play button to run the game. Notice that nothing is happening at the moment. This is because you still need to apply a component to the sphere to tell it how it needs to interact with the physics of the game. In this case, you need to make it solid so that it reacts to gravity.

Remember when you created a sphere that was inside a cube? Objects in the physical world don’t exist inside other objects that way, but in a Unity Scene, by default, GameObjects don’t have mass or respond to gravity. To make a GameObject behave like a real-world physical object, you can give it physical properties by adding a RigidBody Component.

To add the RigidBody Component to the Sphere GameObject:

1. In the Hierarchy window, select the Sphere.

2. Select the Add Component button in the Inspector window.

3. Use the search bar to find a Rigidbody component and select it. Note that there are two options available, Rigidbody and Rigidbody 2D. Make sure you select the Rigidbody component, not the 2D one.

4. In the RigidBody Component in the Inspector, select Use Gravity if it is not already selected.

5. To see the effect of these properties, start the game by pressing the Play button, which will display the Game view.

The ball falls and rolls down the steps. If it does not roll, try moving it to a new position using the transform tools and run the game again.

Try variations of this exercise. Move the Sphere GameObject and the Main Camera to get the results you want.

More things to try:

• Add more spheres with RigidBody Components at varying heights.
• Add other primitives and see how they behave.
• Drop objects in different places.
• Rotate the Monument GameObject.

One thing to note is that you can change the properties, values and position of a selected GameObject while the game is running, but when the game is stopped all values will revert back to what they were before the game was started. This is useful to test different parameters during runtime, but if you want the changes to be permanent, you need to make the changes while the game is stopped.

You have seen how to add properties to GameObjects through components, and you used the RigidBody Component to make a GameObject respond to gravity in the Game view. You also saw how the Game view differs from the Scene view, and you manipulated the Main Camera to change the Game view’s display.

Next, you’ll add more components that make GameObjects look more realistic in 3D space