# init(scale:texture:) Creates an object from a single value, a UV-mapped texture, or both. ``` init(scale: Float = 1.0, texture: CustomMaterial.Texture? = nil) ``` ## Parameters `scale` A value from `0.0` to `1.0` to use as the specular value for the material. `texture` An optional UV-mapped image texture. ## Discussion RealityKit automatically draws *specular highlights* for physically based materials using the values of various properties, primarily [`roughness`](/documentation/RealityKit/PhysicallyBasedMaterial/roughness-swift.property) and [`metallic`](/documentation/RealityKit/PhysicallyBasedMaterial/metallic-swift.property). Specular highlights are bright spots of reflected light that appear on shiny objects. -1@2x.png) While many real-world objects can be accurately and realistically simulated with just the core physically based rendering (PBR) properties, you can create additional realistic effects by augmenting the specular highlights. The specular [`scale`](/documentation/RealityKit/CustomMaterial/Specular-swift.struct/scale) and [`texture`](/documentation/RealityKit/CustomMaterial/Specular-swift.struct/texture) values are available to the material’s surface shader, but RealityKit doesn’t render additional specular highlights unless the surface shader function calls `params.surface().set_specular()`. The following Metal code demonstrates using the specular `scale` and `texture` values in a surface shader function to calculate specular highlights, emulating the specular behavior of [`PhysicallyBasedMaterial`](/documentation/RealityKit/PhysicallyBasedMaterial): ```other // Retrieve the opacity scale from the CustomMaterial. float specularScale = params.material_constants().specular_scale(); // Retrieve the entity's texture coordinates. float2 uv = params.geometry().uv0(); // Entities loaded from a USDZ or .reality file use texture coordinates // with a flipped y-axis. This compensates for that. uv.y = 1.0 - uv.y; // Sample the specular texture. auto tex = params.textures(); half specular = tex.specular().sample(textureSampler, uv).r; // Multiply the tint and the sampled value from the texture and assign // the result. specular *= specularScale; params.surface().set_specular(specular); ``` --- 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)