I am trying to create a flying flag using a vertex displacement shader. I did it with the simple gradient noise node. But I read somewhere these nodes are expensive to use. So I try to figure out how to use a custom grayscale gradient png instead. But I don't make it work until. My current work is below: If I use SimpleNoise output to offset the Y of the current position and feed PBR master, it works perfectly. But with the external gradient image, I could not get it done. What am I doing wrong?