Ok, so I believe there’s some confusion going on here. A material parameter value is not the value of the individual material attributes like “Roughness”, “Tangent”, “Normal”, etc. It’s the value of a user defined parameter. Your issue is the fact that you don’t actually have a parameter for your “Roughness” at all…you have a constant value plugged in. You need to create a scalar parameter (hold s key and click in the graph). Name the parameter whatever you want. The name you choose will be the name you put in the call to GetParameterValue. Keep in mind that if you wish to set the parameter programmatically in the future you’ll need to create a dynamic material instance.
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