SceneKit – Loading HDR or EXR lightingEnvironment has no effect

Question

I tried loading an .hdr file to use it as a skybox and use its lighting informations. This is the code I used:

backgroundColor = UIColor.gray 
// check if a default skybox is added

let environment = UIImage(named: "studio_small_09_2k.hdr")
scene?.lightingEnvironment.contents = environment
scene?.lightingEnvironment.intensity = 1.0
scene?.background.contents = environment

Unfortunately I recieve a grey screen and also no errors. Has anyone experience in using hdr files in SceneKit?

XCode Version: 13.2.1 iOS version: 15.3.1 hdr file: https://polyhaven.com/a/studio_small_09

Answer 1

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.