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Creating Basic 3D Objects for AR in Blender

Blender is a free and open source 3D creation suite. It supports the entirety of the 3D pipeline—modeling, rigging, animation, simulation, rendering, video editing, and animation.

Before you start

In this tutorial, we will be using 3 programs, all of which are free to download:

The Blender Home Screen

When starting a new Blender project, this is the first screen you seen. While it may look daunting, we will only be using a few tools in this tutorial to create new objects and perform minor edits on them.
Your screen when starting a new Blender project

Basic Object Manipulation

The vertical toolbar on the left side of the screen is where we'll find most of the options we need for object manipulation.
The left - object manipulation
This toolbar is very similar to what you might see in Photoshop. When an object is selected, these buttons let you edit its basic properties in the viewer window. Most important for our purposes are the Move, Rotate, Scale, and Transform buttons (3rd-6th buttons counting down, in the group of four tools). These let you edit your object in the standard ways you would expect.

Extruding

A slightly more advanced tool that may be useful is the Extrude tool, which allows you to take a single face of your object and pull it outward. To access this tool, you must first change the mode you are in from Object Mode to Edit Mode from the drop down just above the manipulation tools.
Changing from Object Mode...
....to Edit Mode creates some new options for our object!
Now, extruding our default cube once we are in edit mode takes just a few steps. First, just to the right of Edit Mode on the toolbar are 3 options that let us choose whether we want to select points, edges, or faces. The third option allows us to choose a face to extrude.
Select Extrude by Face (highlighted square)
Now pick which face of our default square we want to pull outward:
I chose the top but you can choose any side to extrude
Finally, one of the choices on the expanded Object Manipulation toolbar on the left is called Extrude Region. Choosing this tool will let you pull outward, expanding your object in one direction.
Expanding the object in one direction using the Extrude Region tool

Scene Objects and Object Properties

The toolbar on the right displays both the collection of objects within our current scene and the properties of that object.
Scene Objects and their Properties
The top of the pane lists all the objects in the current scene and allows you to select them or make them visible/invisible (again, very similar to Photoshop). The lower window displays the object properties, which can be edited directly here. This includes the manipulation properties which you can also edit in the viewing frame itself. There are many other properties, but we don't need to worry about them for now.

Adding Basic Objects

Blender comes with a number of pre-created basic objects that you can then manipulate to create what you want. To add a new object, just go to Add on the toolbar next to Object Mode.
Go to the Add dropdown
There are several basic shapes you can chose from to edit for your own needs
Once you have chosen your mesh, you can manipulate it or extrude it as needed to create the object you want.

Exporting your Object for AR

Apple's Reality Composer program allows you to import .usdz 3D files. Unfortunately, Blender doesn't let you automatically export files in this format. I recommend exporting your object as a .glb file, as this will let you keep the texture, then you have two options for a quick conversion:
  1. 1.
    Use Apple's Reality Converter tool to quickly drag-and-drop your model to convert it.
  2. 2.
    Upload your model to Sketchfab and then download it as a .usdz (see tutorial here)
Note that you cannot change the color/texture of imported objects once they are in Reality Composer. As such, you should color/texture your objects in Blender and export as a .glb to keep the material attached. This can be done in the "material" options under the properties of a specific object.