Has anyone else experienced issues with G'MIC not performing as expected on large images?

This is probably best explained with an example:

My original image is 3418 pixels square. If I resize it to 800 pixels square, then run the G'MIC painting filter, I get this - which matches the G'MIC preview.


However, if I run G'MIC on the 3418 pixel image (same settings) I get this. (The preview shows the same as the 800 pixel image)

The preview in G'MIC is intended to be as much precise as possible only with the default selected scale. That's why some filters renders a global view for the image, while others render a 1:1 pixel ratio.
If you zoom/unzoom the preview window, there are absolutely no ways the preview can ensure it will be close to the final image. I had even thought about removing the zooming buttons to be honest (the preview widget is the one provided by default by GIMP).
So, my question is : did you change the preview zoom factor before applying the effect ?

I did indeed. I zoomed out to see the whole image.

Thanks - I think I understand what's happening now. I can see that the effect of the filter will be different on a larger image if it works at a pixel level rather than proportionately to the image size but I hadn't realised the preview was only accurate at 100% zoom.

Gareth

Some filters work proportionally to pixels, but others work proportionally to the image size. It all depends on how the filter author wrote the filter. So using the default zoom level set by the filter is probably best.

Thanks, Iain.

That explains a lot... Often the image effect looks good in the preview but really not as expected and desired (i.e. much too "wispy") in the final result...