# normal A texture map that stores fine surface details for the entity. ``` var normal: CustomMaterial.Normal { get set } ``` ## Discussion *Normal mapping* is a real-time rendering technique that captures fine surface details for a model by using a texture instead of 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. For custom materials, [`normal`](/documentation/RealityKit/CustomMaterial/normal-swift.property) is only used when [`lightingModel`](/documentation/RealityKit/CustomMaterial/lightingModel-swift.property) is [`CustomMaterial.LightingModel.lit`](/documentation/RealityKit/CustomMaterial/LightingModel-swift.enum/lit) or [`CustomMaterial.LightingModel.clearcoat`](/documentation/RealityKit/CustomMaterial/LightingModel-swift.enum/clearcoat) and its surface shader calls `params.surface().set_normal(). T`he normal map texture is still available to your surface shader function when using [`CustomMaterial.LightingModel.unlit`](/documentation/RealityKit/CustomMaterial/LightingModel-swift.enum/unlit). The following code loads a normal map texture and uses it to set this property: ```swift if let normalResource = try? TextureResource.load(named:"entity_normals") { let normalMap = MaterialParameters.Texture(normalResource) material.normal = .init(texture:normalMap) } ``` The following Metal code shows how to sample the normal map texture in a surface shader and use it to set the fragment’s surface normal: ```cpp // Retrieve the entity's texture coordinates. float2 uv = params.geometry().uv0(); // Entities loaded from USDZ or .reality files have texture coordinates // with a flipped y-axis. This adjusts for that. uv.y = 1.0 - uv.y; // Sample the normal map to get the surface normal for this fragment. auto tex = params.textures(); float3 color = (float3)tex.normal().sample(textureSampler, uv).rgb; // Set the fragment's surface normal using the sampled value. params.surface().set_normal(color); ``` For more information on creating custom materials and writing shader functions, see [Modifying RealityKit rendering using custom materials](/documentation/RealityKit/modifying-realitykit-rendering-using-custom-materials). --- 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)