Using a Mtltexture as the Environment Map of a Scnscene

Using a MTLTexture as the environment map of a SCNScene

Lighting SCN Environment with an MTK texture

Using Xcode 13.3.1 on macOS 12.3.1 for iOS 15.4 app.

The trick is, the environment lighting requires a cube texture, not a flat image.

• Create 6 square images for MetalKit cube texture

• in Xcode Assets folder create Cube Texture Set

• place textures to their corresponding slots

• mirror images horizontally and vertically, if needed

Paste the code:

import ARKit
import MetalKit

class ViewController: UIViewController {

    @IBOutlet var sceneView: ARSCNView!
    
    override func viewDidLoad() {
        super.viewDidLoad()    
        let scene = SCNScene()
        
        let imageName = "CubeTextureSet"
        let textureLoader = MTKTextureLoader(device: sceneView.device!)

        let environmentMap = try! textureLoader.newTexture(name: imageName, 
                                                    scaleFactor: 2, 
                                                         bundle: .main, 
                                                        options: nil)
        
        let daeScene = SCNScene(named: "art.scnassets/testCube.dae")!

        let model = daeScene.rootNode.childNode(withName: "polyCube", 
                                             recursively: true)!
        
        scene.lightingEnvironment.contents = environmentMap
        scene.lightingEnvironment.intensity = 2.5
        scene.background.contents = environmentMap

        sceneView.scene = scene
        sceneView.allowsCameraControl = true
        scene.rootNode.addChildNode(model)
    }
}

Apply metallic materials to models. Now MTL environment lighting is On.

If you need a procedural skybox texture – use MDLSkyCubeTexture class.

Also, this post may be useful for you.

SceneKit – Loading HDR or EXR lightingEnvironment has no effect

I usually use a Cube Texture Set, where each of 6 images is square (height == width).

Also, the following cube map representations are supported:

• Vertical strip as single image (height == 6 * width)
• Horizontal strip as single image (6 * height == width)
• Spherical projection as single image (2 * height == width)

Here's a SwiftUI code:

func makeUIView(context: Context) -> SCNView {

    let sceneView = SCNView(frame: .zero)
    sceneView.scene = SCNScene()
    // if EXR or HDR is 2:1 spherical map, it really meets the requirements
    sceneView.scene?.lightingEnvironment.contents = UIImage(named: "std.exr")
    sceneView.backgroundColor = .black
    sceneView.autoenablesDefaultLighting = true
    sceneView.allowsCameraControl = true
    
    let node = SCNNode()
    node.geometry = SCNSphere(radius: 0.1)
    node.geometry?.firstMaterial?.lightingModel = .physicallyBased
    node.geometry?.firstMaterial?.metalness.contents = 1.0
    sceneView.scene?.rootNode.addChildNode(node)
    return sceneView
}

Pay particular attention – you need .physicallyBased lighting model to get HDR or EXR reflections.

And let's set it for BG:

sceneView.scene?.background.contents = UIImage(named: "std.exr")

Why your .exr doesn't work?

The solutions is simple: delete your .exr from project, empty the Trash and after that drag-and-drop .exr file, in Choose options for adding these files window choose Add to targets:

Now your .exr must work.

SceneKit – How can I programmatically adjust 'Sun elevation' parameter?

You can simultaneously use MDL Sky Box for scene lighting and for BG:

sceneView.scene?.background.contents = MDLSkyCubeTexture(name: "procedural sky",
                                              channelEncoding: .float32,
                                            textureDimensions: vector_int2(512,512),
                                                    turbidity: 0.12,
                                                 sunElevation: 1.00,
                                    upperAtmosphereScattering: 0.05,
                                                 groundAlbedo: 0.32)

sceneView.scene?.lightingEnvironment.contents = sceneView.scene?.background.contents

sceneView.scene?.lightingEnvironment.intensity = 2.0

access particular set of pixels MTLTexture in metal

Yes, as a look at the MTLTexture documentation would have shown you. You can use one of the getBytes() methods to copy a region of texture data out to a buffer, and one of the replace() methods to replace a region of the texture's pixel with data from a buffer you supply.

---

Related Topics