I've loaded a ShaderGraphMaterial from a RealityKit content bundle and I'm attempting to access the initial values of its parameters using getParameter(handle:), but this method appears to always return nil:
let shaderGraphMaterial = try await ShaderGraphMaterial(named: "MyMaterial", from: "MyFile")
let namedParameterValue = shaderGraphMaterial.getParameter(name: "myParameter")
// This prints the value of the `myParameter` parameter, as expected.
print("namedParameterValue = \(namedParameterValue)")
let handle = ShaderGraphMaterial.parameterHandle(name: "myParameter")
let handleParameterValue = shaderGraphMaterial.getParameter(handle: handle)
// Expected behavior: prints the value of the `myParameter` parameter, as above.
// Observed behavior: prints `nil`.
print("handleParameterValue = \(handleParameterValue)")
Is this expected behavior?
Based on the documentation at https://developer.apple.com/documentation/realitykit/shadergraphmaterial/getparameter(handle:) I'd expect getParameter(handle:) to return the value of the parameter, just as getParameter(name:) does.
I've tested this on iOS 18.5 and iOS 26.0 beta 2.
Assuming this getParameter(handle:) works as designed, is the following ShaderGraphMaterial extension an appropriate workaround, or can you recommend a better approach?
Thank you.
public extension ShaderGraphMaterial {
/// Reassigns the values of all named material parameters using the handle-based API.
///
/// This works around an issue where, at least as of RealityKit 26.0 beta 2 and
/// earlier, `getParameter(handle:)` will always return `nil` when used to read the
/// initial value of a shader graph material parameter read using
/// `ShaderGraphMaterial(named:from:in:)`, whereas `getParameter(name:)` will work
/// as expected.
private mutating func copyNamedParametersToHandles() {
for parameterName in self.parameterNames {
if let value = self.getParameter(name: parameterName) {
let handle = ShaderGraphMaterial.parameterHandle(name: parameterName)
do {
try self.setParameter(handle: handle, value: value)
} catch {
assertionFailure("Cannot set parameter value")
}
}
}
}
}
