private void Update(EvaluationContext context)
        {
            var buffer = PrimaryBuffer.GetValue(context);

            if (buffer == null)
            {
                buffer = Fallback.GetValue(context);
            }

            Output.Value = buffer;
        }
        private void Update(EvaluationContext context)
        {
            var tex = TextureA.GetValue(context);

            if (tex == null)
            {
                tex = Fallback.GetValue(context);
            }

            Output.Value = tex;
        }