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Import Cheetah3D Model in SceneKit

This article is really for 3D rookies like me that would like to play with SceneKit. SceneKit[1] is a high-level 3D framework, introduced in Mountain Lion, that allows reading, manipulating and displaying 3D scenes. SceneKit is now part of iOS, starting from iOS 8, allowing developers to easily integrate 3D graphics or develop 3D casual games on iPhone / iPad / iOther.

SceneKit supports the import of COLLADA scenes: COLLADA is an open XML file format for 3D assets, supported by a lot (if not all) 3D creation softwares (like Blender, Maya, Bryce etc…). If you’re new to 3D and just want to play with SceneKit, you can search for free COLLADA files on the web (*.dae), or use the ones included in Apple SceneKit samples (Vehicle, Bananas, or even the complete WWDC 2014 SceneKit session, available as a sample code!)

Besides using free models, you can also create your own using a 3D modelling tool: there are plenty of choices from free (Blender) to very expensive (Maya). On the mac, Cheetah3D is really an excellent, and not very expensive, alternative. For $69, you have a complete 3D modelling, rendering and animation software for OSX (buy directly on Cheetah3D web site or on the Mac App Store).

I’m just beginning to use Cheetah3D, and I really appreciate how easy is the creation of 3D models. Cheetah3D is also a native Cocoa app, with an intuitive, Macintosh-like user interface:

Cheetah3DCheetah3D on Mavericks.

Really a great software!

I’ve created this mug in a couple of minutes, following the first tutorial of Learn 3D with Cheetah3D 6, an excellent resource on Cheetah3D. To include this model in an iOS sample app, we need to first export it as a COLLADA file from Cheetah3D. Select File > Export, choose dae as File Format and save your file (or download it here).

Then, create a SceneKit sample, with Xcode 6: New Project > Single View Application.

SceneKit sample step 1

Give it a product name:

SceneKit sample step 2

Select the main storyboard of the document, Main.storyboard , then the ViewController scene, and remove the default view of the ViewController.

SceneKit sample step 3

Now, in the right corner of Xcode, select the Object library (as in the screenshot), and drag and drop a SceneKit view on the view controller.

SceneKit sample step 4

Now, some code! Open ViewController.m and add the following code:

@import SceneKit;
…
@implementation ViewController
…
- (void)viewDidLoad
{
    [super viewDidLoad];

    SCNView *myView = (SCNView *)self.view;
    myView.scene = [SCNScene sceneNamed:@"mug.dae"];
    myView.allowsCameraControl = YES;
    myView.autoenablesDefaultLighting = YES;
    myView.backgroundColor = [UIColor lightGrayColor];
}

We’ve just loaded our mug COLLADA file into the 3D scene view. Now, we need to import the file into our project: File > Add Files to "TestSK" and select our our mug.dae file. Then build and run:

SceneKit sample step 5

Mmmm… Something must be missing, we don’t have any textures displayed in the simulator! In fact, we forget something really important when importing our COLLADA files from Cheetah3D. In COLLADA files, textures are referenced and not included in the file; in other terms, the mug.dae file is not sufficient, and must be accompanied by the textures files that it references. So, we just need to include our mug-diffuse.png texture in our project: File > Add Files to "TestSK" and select the mug-diffuse.png file. Before running again the sample, you can select the mug.dae file in Xcode, and check that everything looks good now:

SceneKit sample step 6

Then, run the sample, et voilà !

iOS SimulatorThe mug in the iOS simulator

More on SceneKit

WWDC 2012 - Session 504: Introducing Scene Kit

WWDC 2013 - Session 500: What’s New in Scene Kit

WWDC 2014 - Session 609: What’s New in SceneKit

WWDC 2014 - Session 610: Building a Game with SceneKit

From jc.

  1. Spelled "Scene Kit" on Mountain Lion and Mavericks, and "SceneKit" on iOS 8 / OSX Yosemite 

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