Xcode – RealityKit: Incorrect Shadows with Directional Light

I have a problem with shadows in RealityKit and DirectionalLight.

After doing some research from my initial question about this, I downloaded an Xcode project that describes the basics of lights in RealityKit. It’s simple enough.

One of the examples used in that sample project involved a DirectionalLight, which can be very helpful for lighting like the sun.

I took a look at the DirectionalLight option in the app, and added an extra sphere the scene:

Here’s the lighting for that:

private func addDirectionalLight() {
        let directionalLight = DirectionalLight()
        directionalLight.light.intensity = 100000
        directionalLight.shadow?.maximumDistance = 5
        directionalLight.shadow?.depthBias = 1
        directionalLight.look(at: [0, 0, 0], from: [-50, 20, 0], relativeTo: nil)
        
        addLight(directionalLight)
    }

I made the intensity of it pretty high so you can easily see the light (white part) vs the shadows (non-white part).

I then went to my own project.

I want to create a directional lighting setup to achieve an effect akin to the sun. I thought that would be easy… I would just have to look at how the sample project did it and make adjustments.

Well… I tried creating my own lighting setup as follows:

let directionalLight = DirectionalLight()
        directionalLight.light.intensity = 100000
        directionalLight.shadow?.maximumDistance = 3
        directionalLight.look(at: [0, 0, 0], from: [0, 100, 1200], relativeTo: nil)
        // directionalLight.orientation = simd_quatf(angle: .pi/2, axis: [0, 1, 0])
        
        lightAnchor.addChild(directionalLight)

where lightAnchor is an AnchorEntity at [0, 0, 0] for the world.

Here’s the result when applied to objects:

Do you notice anything? I circled it. It’s like the lighting is being applied to each individual object without any sort of regard for the fact that another object is there.

In real life, a shadow would be casted from the sphere on top of the cube in addition to the shadow that is currently present. Look at the first image and pretend it is the top of the cube from the second photo. Yes, there’s a shadow on the back of the sphere where the light doesn’t hit, but ALSO on the plane it’s on.

I am extremely confused.

The only thing I thought of is that the first image has a scale where the sphere in the center of the photo is about 3 meters wide… while my second image is at a much, much larger scale. That box is 150 meters wide.

But, that should not impact the lighting, right? I don’t believe it should. Is my DirectionalLight in a bad position? I don’t understand how it would be, considering that it hit box and sphere.

I simply want shadows like in the first image, but for some reason I cannot achieve that.

I really need some help on this. It would be amazing if someone could!

Also, happy Vision Pro day! 🙂

EDIT 1/2:

I changed to my actual model (which is just one, big USDZ — the first photos were just using example meshes) and lighting code to this:

let directionalLight = DirectionalLight()
        directionalLight.light.intensity = 10000
        directionalLight.shadow?.depthBias = 0.5
        directionalLight.shadow?.maximumDistance = 3
        directionalLight.orientation = simd_quatf(angle: -.pi/5, axis: [1, 0, 0])
        
        lightAnchor.addChild(directionalLight)

This results in shadows looking like this:

It looks kind of weird. I have tried looking at the documentation, but I still don’t understand why I am not getting this right.

EDIT 2/2:

I have discovered another interesting property about shadows in relation to the PerspectiveCamera.

After thinking that the large dimensions of my model had an impact on the absence of shadows, I scaled down the model by a considerable amount.

This did actually partially solve the issue. I could now observe shadows on parts of my model:

I then moved the PerspectiveCamera that I created back from the model a bit:

You have to look carefully here. Compare the two photos. I circled one particular part of the model where the change is very clear. The shadows moved, and even disappeared.

This also happens when I change the fieldOfViewInDegrees on the PerspectiveCamera.

This is very odd behavior. Why would the camera impact the shadows at all? Rendering settings? It’s like I need to ignore the rendering settings and have them not change based on where the camera is/FOV/zoom level etc. Any solutions?

I really have no idea what to do and I’m worried. Especially since I want to animate the camera (or model) moving and zooming in/out. I also want to animate the position of the DirectionalLight.

Perhaps I need a more detailed explanation of depthBias and maximumDistance and how they relate to the PerspectiveCamera, its FOV and rendering.