# init(_:) Creates an object containing surface details for an entity from a custom material’s normal property. ``` init(_ value: PhysicallyBasedMaterial.Normal) ``` ## Parameters `value` The normal object from a [`PhysicallyBasedMaterial`](/documentation/RealityKit/PhysicallyBasedMaterial). ## Discussion This initializer creates an object by copying the normal map from the [`normal`](/documentation/RealityKit/PhysicallyBasedMaterial/normal-swift.property) property of a [`PhysicallyBasedMaterial`](/documentation/RealityKit/PhysicallyBasedMaterial). *Normal mapping* is a real-time rendering technique that captures fine surface details for a model by using a texture instead of by increasing the number of polygons in the model. It works by storing *surface normals*, which are vectors perpendicular to the surface of the model, from a much higher-resolution version of the same 3D object. A normal map stores each vector in the image by storing the vectors’ `X`, `Y`, and `Z` values as the `R`, `G`, and `B` components of the corresponding pixel in the UV-mapped image. To render an entity using a normal map, set [`lightingModel`](/documentation/RealityKit/CustomMaterial/lightingModel-swift.property) to [`CustomMaterial.LightingModel.lit`](/documentation/RealityKit/CustomMaterial/LightingModel-swift.enum/lit) or [`CustomMaterial.LightingModel.clearcoat`](/documentation/RealityKit/CustomMaterial/LightingModel-swift.enum/clearcoat), and call `params.surface().set_normal()` from its surface shader. The following Metal code demonstrates how to sample and use a value from the normal map in your surface shader function: ```swift // Retrieve the entity's UV texture coordinates. float2 uv = params.geometry().uv0(); // Models loaded from USDZ or Reality Composer use UVs that are flipped // on the y-axis. This compensates for that. uv.y = 1.0 - uv.y; // Sample the normal map texture based on the resulting UV coordinates. auto tex = params.textures(); float3 normal = (float3)tex.normal().sample(textureSampler, uv).rgb; // Set the sampled value as this pixel's normal. params.surface().set_normal(normal); ``` --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)