Make a tower of prefab blocks

1. Overview

In this tutorial, you’ll create a few block towers that your bouncing ball will be able to knock over.

When you’re ready to get started, go to the next step.

2. Add a block and reset its Transform

You’re about to begin the construction of your block tower.

To make your first building block, you’ll start by adding a primitive cube. Just like you did with the sphere, you’ll add it to the scene, rename it, then reset its position to the origin as a starting point.

However, this time you’ll use a new technique for creating the new 3D object and a new technique for resetting the object’s position.

Instructions

1. At the top of the Hierarchy window, select the Add (+) button to access the Create menu, then select 3D Object > Cube.

This technique gets you to the same menu as right-clicking an empty area in the Hierarchy window.

2. Rename the cube “Block”.

3. In the Inspector window, select the More (⋮) menu in the upper-right corner of the Transform component and select Reset to reset the cube’s Transform properties, including resetting its position to the origin (0,0,0).

This should position the cube in the center of the room, halfway sunk into the floor.

3. Reposition and scale the block

In this step, you’ll reposition the block so that it’s in the path of the ball and edit its scale so that it looks more like a classic kid’s building block.

However, rather than editing the scale in the Transform component directly like you did with the ball, you’ll actually use the Scale tool in the Scene view.

After you master the Scale tool, you’ll have mastered the three most important tools in the Scene view: Move, Rotate, and Scale.

Instructions

1. In the Hierarchy window, select the Block GameObject.

2. Use the Move tool to reposition the cube above the floor where it will get hit by the ball.

3. Select the Scale tool and use the X, Y, and Z handles to scale it down so it’s a tall, skinny block that the ball can knock over. You can confirm in the Inspector window, but it should be about 0.1, 0.25, 0.1 on the X, Y, and Z scale values.

Tip: For faster editing, flip between the Move, Rotate, and Scale tools using the W, E, and R keyboard shortcuts in the Scene view.

4. Press F to frame the object in the Scene view for a clearer look and make sure that it’s sitting just above the floor.

Remember, you can always undo any unwanted edits with Ctrl+Z (macOS: Cmd+Z).

5. Enter Play mode to see the ball unable to knock over the block, which is something you’ll fix in the next step

6. Exit Play mode.

4. Add Rigidbody Component

In this step, you’ll add a Rigidbody component to the Block GameObject.

Initially, the block won’t move when hit by the ball, acting like an immovable brick wall. This behavior is due to the lack of a Rigidbody component, which governs the physics properties of the GameObject.

With a Rigidbody component, the block can react to a collision and fall over.

Instructions

1. With the Block GameObject selected, select Add Component at the bottom of the Inspector window, then search for and add a Rigidbody component.

2. Enter Play mode to test the interaction.

Observe that the block now gets knocked over when hit by the ball.

Note: Remember to save your scene often with Ctrl+S (macOS: Cmd+S).

5. Create a Block Prefab

In this step, you’ll transform the Block GameObject, which you've already enhanced with a Rigidbody component, into a reusable prefab.

Prefabs in Unity are GameObjects, with all their components and properties already set up, that you can reuse as a template. You can keep these custom prefabs in a folder in the Project window for future use.

Instructions

1. In the Project window, navigate inside the Prefabs folder.

2. Select the Add (+) button at the top of the Project window, then select Folder and name the new folder “My Prefabs”.

Tip: Just like you did in the Hierarchy window, you can access this Create menu using the (+) button or by right-clicking in an empty space in the Project window.

3. Click and drag your Block GameObject from the Hierarchy window into the My Prefabs folder in the Project window.

Note: When you drag a GameObject from the Hierarchy window into any folder in the Project window, it converts the object into a prefab.

Observe that the block in the Hierarchy window turns blue, indicating it is a copy — or an instance — of a prefab.

6. Create a tower from prefab blocks

Now you’ll use the block prefab you created to build a small tower in your Unity scene. The process of constructing a tower not only tests your ability to use prefabs efficiently, but it also allows you to experiment with object positioning in Unity.

Note: The tower doesn’t need to be perfect! As long as it stands up, it'll work well. In fact, it may even be more visually interesting if it’s not perfectly aligned.

Instructions

1. From the Scene view toolbars, locate the Center / Pivot dropdown and make sure that Center is selected.

Note: If the "Center/Pivot" and "Global/Local" buttons aren’t visible in your editor by default, click the three vertical dots in the top-right corner of the Scene window, go to the Overlay Menu, and check the eye icon next to Tool Settings to enable them.

If Pivot is active, your blocks will end up halfway through the floor at their pivot point.

2. Drag multiple instances of the Block prefab from the Project window into your scene, positioning them to form a tower.

Hint: In order to make sure your blocks are aligned, you should examine the tower from all angles. Sometimes it might look aligned from one angle, but not from another. Try framing the block you’re working with, then orbiting it or using the Scene view gizmo to examine it from different angles.

3. After constructing your tower, enter Play mode to observe how the tower behaves.

4. Exit Play mode and make any necessary adjustments to the position of the blocks to refine your tower's stability or design.

7. Reduce the weight in prefab editing mode

You might have noticed that the ball had a hard time knocking over all those blocks. By default, the Rigidbody component sets an object’s mass to 1.0 kilogram (kg). Your 1kg ball is trying to knock over a tower made of three 1kg blocks!

In this step, you will reduce the weight of your Block prefab, and in doing so, reduce the weight of every block in the scene — that’s the beauty of prefabs!

To do this, you'll enter prefab editing mode, a powerful feature in Unity that allows you to edit a prefab asset directly. Prefab editing mode isolates the prefab, enabling you to make changes without affecting the rest of your scene.

Instructions

1. In the Unity Editor, locate your Block prefab in the Project window.

2. Double-click the Block prefab to enter prefab editing mode.

This mode allows you to make changes to the prefab independently of your scene. You’ll know you’re in prefab editing mode when the rest of your scene disappears from the Scene view and you can only see the block.

3. With the Block prefab in prefab editing mode, navigate to the Rigidbody component in the Inspector window and reduce the Mass property to 0.1kg.

4. To exit prefab editing mode, select the small back arrow at the top of the Hierarchy window.

This action will return you to the main scene.

5. After exiting prefab editing mode, test the changes by entering Play mode. Observe how the ball can now much more easily knock over the tower.

Remember to exit Play mode when you’re done testing.

8. Add a material to the prefab

In this step, you'll change the block’s material using prefab editing mode so it’s not that boring gray anymore. You'll see the power of prefabs once again, as you modify a single asset and see the change instantly reflected across all instances of that prefab.

Instructions

1. Open the Block prefab in prefab editing mode by double-clicking it in the Project window.

This isolates the prefab for editing.

2. In the Inspector window, in the Mesh Renderer component, locate the Material property of the Block prefab.

3. Select the Object picker (⊙) next to the Material property.

This action opens a window displaying all available material assets in your entire project.

4. Browse through the list of materials. You'll see various options, including some designed for furniture, floors, and so on — some of them might have some unintuitive names. Select a material that appeals to you and apply it to the Block prefab.

Note: You can also create your own material like you did for the ball if you don’t see one you like!

5. Exit prefab editing mode by selecting the back arrow at the top of the Hierarchy window.

Observe how the new material is now applied to all instances of the block in your scene.

Note: Remember to save your scene regularly with Ctrl+S (macOS: Cmd+S).

9. Organize blocks with a parent GameObject

In this step, you’ll address the clutter in your Unity project's Hierarchy window caused by numerous Block prefabs.

You'll learn to organize these blocks under a single parent GameObject, simplifying your scene and making it more manageable.

As a reminder, a parent GameObject is a GameObject that serves as a container for other GameObjects, known as child GameObjects. These terms describe a hierarchical relationship, much like a family tree.

Instructions

1. In the Hierarchy window, select the first Block GameObject, then hold down the Shift key and select the last Block prefab in your list to select all blocks in between. You can also hold Ctrl (macOS: Cmd) to select individual additional GameObjects.

2. Right-click the selected blocks and choose Create Empty Parent.

This action creates a new parent GameObject with the individual blocks indented as child GameObjects.

3. Rename this new GameObject something descriptive, like “Block_Tower”.

4. With the Block_Tower GameObject selected, you can move, rotate, and scale the entire group of blocks as one unit.

10. Turn the block tower into a prefab

The block tower you've created consists of multiple individual blocks arranged in a specific structure.

If you convert this entire structure into a prefab, you enable the possibility of reusing this complex object multiple times within your project.

You’ll see that prefabs are particularly beneficial when creating repeated structures or patterns in your game environment.

Instructions

1. In the Hierarchy window, select the Block_Tower GameObject.

2. Click and drag it into the Prefabs > My Prefabs folder within the Project window (next to your Block prefab).

This action converts your GameObject into a reusable prefab.

Now, you can easily create multiple instances of your Block_Tower throughout your scene.

3. Add a few more of these towers to your scene to make for a more interesting collision.

4. Enter Play mode to test the collision path with multiple towers.

Note: If you want, edit the block tower in prefab editing mode to make it a more interesting structure.

11. Adjust the ball's mass

With so many towers in your scene, the ball may once again have a hard time knocking all of the blocks over. But what would happen if the ball was ten times heavier? Or one hundred times heavier?

Instructions

1. Select the Ball GameObject.

2. In the Inspector window, in the Rigidbody component, increase the mass to ensure it topples the block structure when it collides.

3. Enter Play mode and watch the blocks fly!

Note: Remember to save your scene often with Ctrl+S (macOS: Cmd+S).

12. Review and proceed to next tutorial

Congratulations on creating a fun block tower experiment for the kids’ bedroom!

Here are some of the things you learned how to do along the way:

• Reset the Transform component to reposition an object at the origin.

• Scale objects with the Scale tool.

• Explain how to use prefabs in a scene.

• Make a new prefab from an existing GameObject in a scene.

• Identify a prefab instance in the Hierarchy window.

• Switch the tool handle position of a GameObject between Center and Pivot.

• Edit a prefab in prefab mode.

• Assign a material to a GameObject by changing the Mesh Renderer component.

• Make an empty GameObject as a parent for other GameObjects.

• Arrange GameObjects in parent-child relationships using the Hierarchy window.
  

Instructions

Proceed to the next tutorial where you'll edit the lighting, change the background, and position your camera for a perfect shot of your scene.