following a thread here (3rd page post by Rod)
thread
I tried Rods way using the warp map filter in gmic
Robs steps:
" Works pretty nice with just 2 layers.
The desaturated layer and a checkerboard layer.
Select the checkerboard layer and run G'MIC>Testing>GarageCoder>Warp Map"
I didn't use a checkerboard layer but an empty layer I had filled with a pattern.
applying the warp map didn't produce any effect!

Thes are the steps I tried
desaturate the bottom layer (with the image on)
make an empty layer above the desaturated one and fill with a pattern/design (edit fill with pattern)
then;
Select the pattern layer and run G'MIC>Testing>GarageCoder>Warp Map
blend mode softglight selected in the filter dialogue

It works for me. Have you enabled the multi-layer input mode in the plug-in (basically 'Input Layers' -> 'All') ?
If this option is set to 'active layer', this won't produce any effect.

@ Ronounours
NO! and that was the reason, thank you!
I havent used Gmic much.