How to Hollow Out Objects in Blender: Practical Tips and Techniques

Written by Daisie Team

Published on 19 June 2023 7 min read

Creating a hollow object in Blender can be a useful skill to have, especially if you're working on 3D printing projects or designing objects with an inner cavity. In this guide, we will walk you through the process of hollowing out an object in Blender using practical tips and techniques. Follow along, and you'll soon be able to master the art of making a blender hollow out object!

1. Preparing the Object

Before you can hollow out an object in Blender, you need to prepare it by importing and scaling it, as well as checking its normals. This will ensure that your object is ready to be hollowed out using various techniques.

1.1 Importing and Scaling

To start, follow these steps:

Open Blender and create a new file or open the file containing the object you want to hollow out.
If necessary, import your object using File > Import and selecting the appropriate file type.
Ensure your object is properly scaled by selecting it and pressing S to scale it. You can also use the Transform panel in the Properties window to adjust the scale values.

1.2 Checking Normals

Normals are important because they define the direction of the faces in your object. If they're not facing the right way, you might encounter issues when hollowing out your object. Here's how to check and correct normals:

Select your object and enter Edit Mode by pressing Tab.
Press A to select all faces of your object.
Go to Mesh > Normals > Recalculate Outside to fix any flipped normals.
To visualize the normals, enable Face Orientation in the Viewport Overlays panel. Blue faces are facing outwards, while red faces are facing inwards. Correct any incorrect normals by selecting them and pressing Shift + N.

With your object prepared, you are now ready to explore different techniques for hollowing it out in Blender.

2. Solidify Modifier

The Solidify Modifier is an easy and effective way to create a Blender hollow out object. It adds thickness to your object by extruding its faces inward or outward. Let's explore how to use this modifier to hollow out your object efficiently.

2.1 Setting Thickness

To set the thickness of your hollow object using the Solidify Modifier, follow these steps:

Select your object and go to the Modifiers tab in the Properties window.
Click on Add Modifier and choose Solidify from the list.
Adjust the Thickness value to determine the thickness of your object's walls. A negative value will create an inward extrusion, while a positive value will create an outward extrusion.
Use the Offset slider to control the position of the new geometry relative to the original geometry. An offset of 0 will place the new geometry in the middle, while an offset of 1 or -1 will place it along the inner or outer surfaces, respectively.
Enable Even Thickness to ensure a uniform thickness throughout the object.

2.2 Applying Modifier

Once you're satisfied with the thickness and offset settings, you'll need to apply the Solidify Modifier to make the changes permanent. To do this:

In the Modifiers tab, click on Apply to apply the Solidify Modifier to your object.
Switch to Edit Mode (press Tab) and inspect your object to ensure the hollowing process was successful.

Now that you've used the Solidify Modifier to create a Blender hollow out object, let's explore another technique - the Boolean Modifier.

3. Boolean Modifier

The Boolean Modifier is another effective method to hollow out objects in Blender. It allows you to create a hollow space inside your object using another object as a "cutter." Let's learn how to use the Boolean Modifier to achieve this.

3.1 Creating Interior Object

First, you need to create an interior object that will define the hollow space inside your main object. Follow these steps:

Add a new object that matches the shape of your main object but is slightly smaller. For example, if your main object is a cube, add a smaller cube inside it.
Position the new object so that it's completely inside the main object and covers the desired hollow space.
Make sure the new object does not intersect with any existing geometry or protrude from the main object.

3.2 Subtracting Interior

Now let's use the Boolean Modifier to subtract the interior object from the main object and create the desired hollow space:

Select the main object and go to the Modifiers tab in the Properties window.
Click on Add Modifier and choose Boolean from the list.
Set the Operation to Difference to subtract the interior object from the main object.
Click on the Object field and select the interior object you created earlier.
Click on Apply to apply the modifier and create the hollow space inside the main object.
Delete or hide the interior object, as it's no longer needed.

With the Boolean Modifier, you've successfully created another Blender hollow out object. However, there's one more technique we can explore: manual hollowing.

4. Manual Hollowing

If you prefer to have more control over the hollowing process, manual hollowing is a great option. This method involves extruding and scaling faces to create the hollow space. Let's dive into the details of how to hollow out objects in Blender manually.

4.1 Extruding Faces

To start with manual hollowing, follow these steps:

Select your object and enter Edit Mode (Tab key).
Select all faces (A key) that you want to extrude to create the hollow space.
Press the E key to extrude the selected faces, but don't move them yet.
Press the Esc key to cancel the extrusion movement, leaving the new faces in place.

Now that you have extruded the faces, it's time to scale and move them to create the hollow space inside your object.

4.2 Scaling and Moving

Follow these steps to scale and move the extruded faces:

With the new faces still selected, press the S key to scale them down to the desired thickness of the hollow space.
Press the G key to move the scaled faces inward, creating the hollow space inside your object.
Adjust the position of the extruded faces as needed to achieve the desired hollow shape.
Exit Edit Mode (Tab key) and check your object to ensure the hollow space looks as intended.

By manually hollowing your object, you have full control over the process, allowing you to create custom hollow shapes in Blender easily. Now it's time to optimize your model before finalizing it.

5. Optimizing the Model

After hollowing out your object in Blender, it's essential to optimize the model to ensure its quality and performance. This includes removing doubles, fixing non-manifold issues, and recalculating normals. Let's go through each step in detail.

5.1 Removing Doubles

Removing doubles is an important step to clean up your model and reduce its complexity. Follow these steps to remove doubles:

Select your object and enter Edit Mode (Tab key).
Select all vertices (A key).
Press the M key, followed by the By Distance option to merge overlapping vertices automatically.
Exit Edit Mode (Tab key).

This process will help you eliminate any unnecessary vertices and make your model more efficient.

5.2 Fixing Non-Manifold Issues

Non-manifold issues can cause problems with your model, especially when 3D printing. Here's how to fix non-manifold issues in Blender:

Enter Edit Mode (Tab key) and select all vertices (A key).
Press the Shift + Ctrl + Alt + M keys to select non-manifold elements.
Inspect the selected areas and manually fix any issues, such as disconnected vertices or overlapping faces.
Exit Edit Mode (Tab key).

By fixing non-manifold issues, you'll ensure that your hollow object is ready for further use, such as 3D printing or game asset creation.

5.3 Recalculating Normals

Normals define the direction each face is pointing in your model. It's crucial to have consistent normals for a proper hollow object. Here's how to recalculate normals in Blender:

Enter Edit Mode (Tab key) and select all vertices (A key).
Press the Shift + N keys to recalculate the normals.
Exit Edit Mode (Tab key).

Recalculating normals will ensure that the faces of your hollow object are pointing in the correct direction, improving the overall quality of your model.

Now that you've optimized your model, it's time to add some final touches to enhance its appearance and export it for use in other applications.

6. Final Touches

With your hollowed-out object optimized, it's time to add some final touches to enhance its appearance and prepare it for use in other applications, such as 3D printing or game development. Let's cover smoothing the model and exporting it in the right format.

6.1 Smoothing the Model

Smoothing your model can improve its appearance by reducing sharp edges and corners. Here's how to smooth your hollow object in Blender:

Select your object in Object Mode (Tab key).
In the Object Data Properties panel, click on the Normals tab.
Enable the Auto Smooth option and adjust the Angle value to achieve the desired smoothness.

By smoothing your model, you'll give it a more polished look, making it more visually appealing for its intended use.

6.2 Exporting the Model

Finally, after hollowing out and optimizing your object, you'll want to export it in the right format for use in other applications. Here's how to export your hollow object in Blender:

Select your object in Object Mode (Tab key).
Go to File > Export and choose the desired file format, such as .STL for 3D printing or .OBJ for game assets.
In the export settings, tick the Selection Only option to export only your selected object.
Choose a file destination and click on Export.

With your hollow object exported, you're now ready to use it in your preferred application, whether it's 3D printing, game development, or any other creative project.

In summary, learning how to hollow out objects in Blender is a valuable skill that can open up new possibilities in your 3D creations. By following the practical tips and techniques outlined in this guide, you'll be able to master the process and create impressive hollow objects for a wide range of applications. Happy blending!

If you're looking to further develop your skills in 3D art, don't miss the workshop 'Creating 3D Art: How To Build a Room in Blender' by Jonathan K. This workshop will teach you the essential techniques for building a realistic room in Blender, helping you bring your creative ideas to life in 3D.