# custom User-defined properties for the material’s shader functions. ``` var custom: CustomMaterial.Custom { get set } ``` ## Discussion Use a [`CustomMaterial.Custom`](/documentation/RealityKit/CustomMaterial/Custom-swift.struct) object to send custom data to your shader functions. A custom object can hold a texture or a vector value, or both. Both the texture and vector value are available in your shader functions. > Note: Unlike other ``doc://com.apple.RealityKit/documentation/RealityKit/CustomMaterial`` properties, you don’t need to > create a ``doc://com.apple.RealityKit/documentation/RealityKit/CustomMaterial/Custom-swift.struct`` object for your > material. All ``doc://com.apple.RealityKit/documentation/RealityKit/CustomMaterial`` objects have one by default; you just > need to set the ``doc://com.apple.RealityKit/documentation/RealityKit/CustomMaterial/Custom-swift.struct/value`` property, > ``doc://com.apple.RealityKit/documentation/RealityKit/CustomMaterial/Custom-swift.struct/texture`` property, or both. The following code demonstrates how to use the custom property to pass a vector to your shader functions: ```swift // Specify a custom vector to pass to the shader functions. customMaterial.custom.value = [0.25, 0.25, 0.25, 1.0] ``` You can also use it to pass up to four scalar values instead of a vector: ```swift let customValue1: Float = 0.25 let customValue2: Float = 0.75 customMaterial.custom.value[0] = customValue1 customMaterial.custom.value[1] = customValue2 ``` The custom property can also include a texture. The following code demonstrates how to add a texture to the custom property: ```swift if let theResource = try? TextureResource.load(named: "MyCustomTexture") { let myTexture = CustomMaterial.Texture(theResource) customMaterial.custom.texture = .init(myTexture) } ``` The following Metal code shows how to retrieve the custom vector in a shader function: ```cpp float4 myCustomVector = params.uniforms().custom_parameter(); ``` The following Metal code shows how to retrieve individual values from the custom vector in your shader functions: ```cpp float firstCustomValue = params.uniforms().custom_parameter()[0]; float secondCustomValue = params.uniforms().custom_parameter()[1]; ``` Here’s how to retrieve the custom texture in your shader functions: ```cpp float voronoiColor = params.textures() .custom().sample(textureSampler, UV).r; ``` --- 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)