public class ToonFilter: TextureSamplingOperation {
    public var threshold: Float = 0.2 { didSet { uniformSettings["threshold"] = threshold } }
    public var quantizationLevels: Float = 10.0 { didSet { uniformSettings["quantizationLevels"] = quantizationLevels } }

    public init() {
        super.init(fragmentShader: ToonFragmentShader)

        ({ threshold = 0.2 })()
        ({ quantizationLevels = 10.0 })()
    }
}
