Created attachment 113920 [details] Comparison of smudge with and without selection Painting with a Color Smudging brush preset inside of a selected area appears to weaken the Smudge Length
I cannot reproduce this. Did you change any other settings (size of the brush, preset settings, flow, opacity)? Could you attach a kra file to make it easier to reproduce?
Created attachment 113921 [details] Video demonstration I haven't made any changes to the brush preset, it is the default one pre-packaged with Krita. I could attach a .kra file if you'd like, but to me this problem isn't bound to any specific project and happens with all smudge brush presets. It might be worth mentioning that I'm not using Instant Preview mode, and I tried turning off Canvas Graphics Acceleration as well, but the problem persists.
I can reproduce it with 4.2.0-pre-alpha (git ae5e111). My simplest steps to reproduce it: Create a new 16-bit integer/channel document. Draw a big enough rectangle with a red color. Select Wet Circle brush Change to a blue color Change its Opacity to 40% Draw over the rectangle Select All Draw over the rectangle The resulting lines are not the same.
Marking this as duplicate of the newer bug as that one's assigned. *** This bug has been marked as a duplicate of bug 423851 ***