Importing 3D Models

Fortunately, it is easy to import existing 3D models into a scene and SceneKit/ARKit support several 3D file formats.

There are an increasing number of websites and creators specializing in pre-made 3D models. I have found free3d.com to be an excellent place to find free and cheap pre-made 3D models.

In Listing 13-1, we can see how simple it is to import a 3D model into our scene.

It is worth noting that once the 3D model has been added to the scene as a SCNNode , it is just like any other SCNNode, so we can change its position, scale, orientation, materials, and so on. In fact, sometimes imported 3D models are far too big for our scene, so we need to change the scale of the nodes before they will fit into our scene.

And of course you can combine other effects we covered in previous chapters with your 3D model. For example, you could use animations to have the 3D model slowly spin or set its opacity to have it slightly transparent or have it fade into the scene.

One thing you must bear in mind when retrieving the 3D model from the file is that you will need to retrieve the specific node you wish to retrieve from the file by name as can be seen in Listing 13-1. Fortunately, Xcode can be quite useful in determining the name of the node you wish to add, as can be seen in Figure 13-1.

public override void ViewDidAppear(bool animated)

{

    base.ViewDidAppear(animated);

    this.sceneView.Session.Run(

       new ARWorldTrackingConfiguration());

    SCNScene sceneFromFile = SCNScene.FromFile(

        "art.scnassets/tree.dae");

    SCNNode model = sceneFromFile.RootNode.FindChildNode(

        childName:"SomeChildName", recursively: true);

    // How to scale or position the node model if needed

    model.Scale = new SCNVector3(0.2f, 0.2f, 0.2f);

    model.Position = new SCNVector3(0, -0.2f, 0);

    this.sceneView.Scene.RootNode.AddChildNode(model);

}

Listing 13-1

Adding a 3D model to a scene

To reiterate, if you have possession of the 3D model file but don’t know the name of the root node, then if you open the file in Xcode, you should be able to click around parts of the model and navigate the scene graph to find the root node name.

Creating Your Own 3D Models in Blender

If you want to create your own 3D models in your Augmented Reality experiences, I strongly recommend you consider learning how to use a 3D modelling tool called Blender . It is something that I am slowly learning myself.

For starters, it is a free tool that is not only powerful but at the same time accessible to beginners willing to put in the time to learn it, and is becoming increasingly popular. In fact, many film studios have started using Blender for creating 3D models and effects rather than using expensive industry standard alternatives. There are also a lot of tutorials online about how to create various 3D models ranging from doughnuts to furniture to castles and cars.

For example, as can be seen in Figure 13-2, using Blender and a plug-in called “BlenderGIS,” we can produce a 3D model of any terrain returned from Google Maps, then export it and use it in our AR experiences.

You can see in Figure 13-2, this example is also using shadows (from Chapter 7, “Lighting”) to help the user to understand how high off the ground it is floating and make it look more real.

Add Shadows, Animations, and Make Interactive

By this point , we have already covered a few other concepts that we can use in conjunction with our 3D models. We can add lighting and shadows to make the 3D models look more real. We can use animations to make the 3D models more dynamic.

Things to Try

You could spend all day playing around with 3D models in your Augmented Reality scenes; however, here are a few ideas of things you could try.

Add a pre-made 3D model to your app.

Obtain a supported, 3D model file, add it to your project, and place it in your scene.

Create a simple model in Blender and use it in your app.

Create a basic model in Blender; it doesn’t have to be complicated. Then export it into a supported file type, add it to your project, then use it in your scene.

Use touch gestures to interact with 3D models in your scene.

Get your 3D model to respond to the touch interactions discussed in Chapter 12, “Touch Gestures and Interaction.”

Add animations to your 3D model.

Use some of the animations (actions) discussed in Chapter 5, “Animations,” to animate the scale, position, or opacity of a 3D model in your scene.

Use 3D models with Image detection.

Try adding a 3D model to an image detected in a scene. You’ll notice that if you rotate the orientation of the detected image, the orientation of the 3D model will change similarly.

Summary

As well as basic 3D shapes, which we learned about previously, you should now be aware of how more complex 3D models can be added to and used in your AR experiences. You can either obtain pre-made ones or even build and use your own using a 3D modelling tool like Blender.

With various models and shapes in our scene now, we should look at ways that we can allow them to simulate interaction with each other and their physical environment through the use of simulated physics. If you are thinking this sounds complicated, don’t worry. ARKit has some built-in physics abilities so that we don’t have to worry about the maths and complexities as we shall see in the next chapter, “Physics.”