This also applies to ar Quick Look.

And https://youtube.com/shorts/U51bsfvQ2FM https://youtube.com/shorts/cFctihaemsI In the first video, iOS 17.5.1, and occlusion works correctly, in the second video, iOS 18.0, and it does not work correctly. The app builds are identical. Here is the shader code. #include <metal_stdlib> #include <RealityKit/RealityKit.h> using namespace metal; constexpr sampler textureSampler(coord::normalized, address::repeat, filter::linear, mip_filter::linear); [[visible]] void pngImage(realitykit::surface_parameters params) { auto surface = params.surface(); float2 uv = params.geometry().uv0() * 8; auto tex = params.textures(); half3 color = (half3)tex.base_color().sample(textureSampler, uv).rgb; half opacity = tex.opacity().sample(textureSampler, uv).r; if (color.r > 0.15 && color.g > 0.15 && color.b > 0.15) { surface.set_emissive_color(color * 1.5); opacity = 0.5; } else { opacity *= 0.0; } params.surface().set_opacity(opacity); } The same problem occurs, for example, with this shader. [[visible]] void strobe(realitykit::surface_parameters params) { auto surface = params.surface(); half3 white = half3(1.0, 1.0, 1.0); params.surface().set_base_color(white); surface.set_base_color(white); surface.set_emissive_color(white); float time = params.uniforms().time(); half opacity = abs (sin (time * 2) * 0.5 + 0.5 ); surface.set_opacity(opacity); }

@DTS Engineer I will try to explain more clearly. The first image shows the correct behavior (iOS 17), while the second shows the incorrect behavior (iOS 18). As you can see, the occlusion is not working. I will also attach two videos of the same build so that you can see the strange behavior on iOS 18. https://youtube.com/shorts/VPCMBiASxLc?feature=share https://youtube.com/shorts/Q8LL4lU2cZE?feature=share You can also try this model in Quick Look on iOS 17 and 18 to see the difference: https://vizbl-2.s3.us-west-1.amazonaws.com/native/cc60dd92-58c2-4867-82a1-55afae8caf9f.usdz The following change was also noticed In iOS 16, 17: materialPlane = UnlitMaterial(color: .init(white: 1.0, alpha: 0.0)) created a fully transparent material. In iOS 18, with this approach, the material becomes fully opaque and white. To fix this, I added: materialPlane?.blending = .transparent(opacity: 0.0) The difference in rendering behavior across different iOS versions is absolutely obvious; something has changed in the post-processing of the alpha value.

After conducting a large number of experiments, I achieved the desired visual result.