It's what I already said... here ➤ https://www.gimp-forum.net/Thread-crease...6#pid38956 and it's what rich2005 shows on the video, please get some focus when reading and follow instruction step by step don't miss one step.
FIRST make the layer "purple copy #1" AND the "crease" layer ➤ as big as the canvas ➤ that's why you don't see anything.
To do so, for each layer go to Layer > Layer to Image Size, once both layers are to the image size,
Then remove the visibility of the "crease" layer by un-ticking the eye in front of it.
Then select the layer "purple copy #1" and go to Filters > Map > Bump Map... and in the window that open click on the button near "Aux input" and select the "crease" layer by double-clicking on it as auxiliary input.
FIRST make the layer "purple copy #1" AND the "crease" layer ➤ as big as the canvas ➤ that's why you don't see anything.
To do so, for each layer go to Layer > Layer to Image Size, once both layers are to the image size,
Then remove the visibility of the "crease" layer by un-ticking the eye in front of it.
Then select the layer "purple copy #1" and go to Filters > Map > Bump Map... and in the window that open click on the button near "Aux input" and select the "crease" layer by double-clicking on it as auxiliary input.
Patrice